Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Osteosarcoma. Core disease mechanisms, molecular and cellular pathways, in...

This report is retrieval-only and is generated directly from Asta results.

• Papers retrieved: 20
• Snippets retrieved: 20

Relevant Papers

[1] Molecular Alterations Associated with Osteosarcoma Development

• Authors: K. Ando, Kanji Mori, F. Verrecchia, B. Marc, F. Redini et al.
• Year: 2012
• Venue: Sarcoma
• URL: https://www.semanticscholar.org/paper/b76a3cc461126c0c00bea324f2db2f8fed2b6e44
• DOI: 10.1155/2012/523432
• PMID: 22448123
• PMCID: 3289857
• Citations: 32
• Influential citations: 1
• Summary: The understanding of the mechanism of molecular alterations can provide the identification of novel therapeutic targets and/or prognostic markers for osteosarcoma treatment to improve the clinical outcome.
• Evidence snippets:
• Snippet 1 (score: 0.582) > Osteosarcoma is the most frequent malignant primary bone tumor characterized by a high potency to form lung metastases which is the main cause of death. Unfortunately, the conventional chemotherapy is not fully effective on osteosarcoma metastases. The progression of a primary tumor to metastasis requires multiple processes, which are neovascularization, proliferation, invasion, survival in the bloodstream, apoptosis resistance, arrest at a distant organ, and outgrowth in secondary sites. Consequently, recent studies have revealed new insights into the molecular mechanisms of metastasis development. The understanding of the mechanism of molecular alterations can provide the identification of novel therapeutic targets and/or prognostic markers for osteosarcoma treatment to improve the clinical outcome.

[2] Three‐Dimensional Osteosarcoma Models for Advancing Drug Discovery and Development

• Authors: Cátia F. Monteiro, C. Custódio, J. Mano
• Year: 2018
• Venue: Advanced Therapeutics
• URL: https://www.semanticscholar.org/paper/61c3479cbd4f975eea03b326fcbb1d60db9d5c1f
• DOI: 10.1002/adtp.201800108
• Citations: 26
• Influential citations: 2
• Summary: This review focuses on the most recent advances in 3D in vitro osteosarcoma models, highlighting the crucial role of the extracellular matrix and stromal cells in tumor progression, how they contribute to drug resistance and disease prevalence, and the future pathways toward an effective and personalized model for drug screening and validation.
• Evidence snippets:
• Snippet 1 (score: 0.559) > Cancer is a complex disease characterized by genetic disorders that are involved in abnormal cell growth and heterogeneous pathophysiology. Osteosarcoma (OS), a rare primary malignant disease, is the most common type of bone cancer that mainly affects children and adolescents, being also found with frequency in adults over 40. [1] Primary OS mainly arise in the long bones of the extremities, with higher incidence in the distal femur, proximal tibia, and proximal humerus. [2] This tumor commonly occurs in the metaphysis, named growth plate of the long bones where the most proliferative cells are located, and preferentially metastasize to the lung both at an initial and later stage. [3,4] OS origin is attributed to several epigenetic and/or genetic alterations in mesenchymal stem cells (MSCs) or MSC-derived osteogenic lineages, such as mutation of p53 and retinoblastoma tumor suppressor gene inactivation, under the influence of specific bone microenvironment signals. The accumulation of these DOI: 10.1002/adtp.201800108 alterations leads to the emergence of cancer stem cells (CSCs) subpopulations with selfrenewal and differentiation capacity, MSC markers expression and increased DNA repair ability, sustaining tumor growth, recurrence, metastasis and drug resistance. [5] The available therapies for OS include neoadjuvant chemotherapy with standard cytotoxic drugs such as doxorubicin, methotrexate, and cisplatin, followed by surgical resection of the primary tumor and adjuvant chemotherapy. [6] Based on National Cancer Database Report 1985-2003, these therapies are not effective, yielding a 5-year survival rate of 53.9% and besides that, patients with metastatic or recurrent disease have an extremely low survival rate (<30%). [7,8] The most critical issue that underlies these values is chemoresistance, for which the understanding of the molecular mechanisms in cancer may produce better clinical outcomes. [3] Nonetheless, the discovery of new anticancer drugs and effective therapies for OS is an emergency. The low OS prevalence

[3] Advancements in Osteosarcoma Therapy: Overcoming Chemotherapy Resistance and Exploring Novel Pharmacological Strategies

• Authors: Mahmoud Zhra, S. Akhund, K. S. Mohammad
• Year: 2025
• Venue: Pharmaceuticals
• URL: https://www.semanticscholar.org/paper/58fd3913b9d9892b2836686a120efcc276513ae7
• DOI: 10.3390/ph18040520
• PMID: 40283955
• PMCID: 12030420
• Citations: 19
• Summary: The need for continued innovation in treating osteosarcoma to improve patient outcomes and survival rates is underscored, with a comprehensive overview of recent advancements in osteosarcoma therapy, particularly in overcoming chemotherapy resistance.
• Evidence snippets:
• Snippet 1 (score: 0.546) > Osteosarcoma (OS) is the most common primary malignant bone tumor in children and young adults, characterized by high metastatic potential and poor prognosis for metastatic cases [16,51]. Standard treatment for osteosarcoma typically includes a combination of surgical intervention and multi-agent chemotherapy. The surgical approach focuses on removing the tumor with adequate margins while maintaining the functionality of the affected limb [12,52]. Pre-operative and post-operative chemotherapy regimens, which include methotrexate, doxorubicin, and cisplatin (MAP), are designed to reduce tumor size before surgery and to eliminate any residual tumor cells afterward [53]. > However, systemic chemotherapy for OS faces significant challenges due to its invasive nature and the pain it causes, which can significantly impact the quality of life of patients [54]. One major issue is that systemic drugs often struggle to reach cancer cells located far from blood vessels, resulting in low drug concentrations in the affected bone. This problem is exacerbated by factors such as drug instability in the bloodstream, protein binding, and clearance by liver cells, which all contribute to toxicity related to the doses given [55]. As a result, high systemic doses are frequently required, which can lead to severe adverse effects, including myelosuppression, hepatotoxicity, cardiotoxicity, and potentially fatal central nervous system complications. Chemotherapy resistance in OS remains a significant obstacle, with over 30% of patients exhibiting resistance to current treatments or experiencing severe side effects, ultimately leading to disease progression and increased mortality [56]. To address these challenges, recent studies have concentrated on developing advanced drug delivery systems aimed at enhancing the effectiveness of chemotherapy while minimizing side effects [57]. Additionally, understanding the mechanisms of chemotherapy resistance is essential for creating new therapeutic strategies to improve patient outcomes.

[4] PERK-mediated Autophagy in Osteosarcoma Cells Resists ER Stress-induced Cell Apoptosis

• Authors: Guang Ji, Nai-chun Yu, Xiang Xue, Zong-guang Li
• Year: 2015
• Venue: International Journal of Biological Sciences
• URL: https://www.semanticscholar.org/paper/99fd43e1347182a3e65102813a6774de48937a4c
• DOI: 10.7150/ijbs.11100
• PMID: 26078722
• PMCID: 4466461
• Citations: 38
• Influential citations: 1
• Summary: This study implicates PERK-mediated autophagy as a significant contributor to apoptosis resistance due to ER stress in osteosarcoma cells, and implicates it as a novel target for improving osteosARcoma therapy.
• Evidence snippets:
• Snippet 1 (score: 0.545) > Osteosarcoma (OS) is a type of bone tumor in which the proliferating spindle cells produce osteoid or immature bone. OS accounts for 2.4 % of all malignancies in pediatric patients and about 20 % of primary bone cancers [1,2]. OS occurs mainly in the metaphysis of long bones around the knee region of the distal femur or proximal tibia. It is highly aggressive and metastasizes mainly to the lung [3]. Recently, advances in clinical treatment have helped much to improve limb salvage and reduce metastases. And multiagent dose-intensive chemotherapy methods have increased the disease-free survival rates in patients with localized disease [4]. However, frequent acquisition of drug-resistant phenotypes is often found in OS chemotherapy. It becomes a significant obstacle to develop better OS clinical treatment. With drug treatment, osteosarcoma cells activate several intracellular protective mechanisms to escape from cell death [5,6]. Earlier reports have been indicated that some strategies are used by osteosarcoma cells to obtain apoptosis resistance, such as PI3K/AKT, MDR-I and survivin pathways [7][8][9][10]. Although much progress has been made, it is still urgent to clarify molecular mechanisms underlying OS chemoresistance for clinical therapy. > In mammalian cells, many mechanisms that modulate cell homeostasis developed to maintain the balance of self construction and destruction. And one of these mechanisms is autophagy [11]. Autophagy is a fundamental lysosomal process that participates in stress tolerance. By autophagy, impaired/disrupted proteins and organelles are recruited to autophagosomes and subsequently degraded by enzymes. It is because of autophagy that intracellular components may be recycled to maintain homeostasis and prevent the accumulation of damaged cell fragements [12].

[5] Novel Therapeutic Savior for Osteosarcoma: The Endorsement of Ferroptosis

• Authors: Cheng Qiu, Tianyi Liu, Dan Luo, D. Luan, Lin Cheng et al.
• Year: 2022
• Venue: Frontiers in Oncology
• URL: https://www.semanticscholar.org/paper/7a6506ef266b707b0015d72bd11a9d196b7bf147
• DOI: 10.3389/fonc.2022.746030
• PMID: 35402247
• PMCID: 8987436
• Citations: 29
• Summary: Four primary regulators involved in ferroptosis are outlined in this article and several critical issues are highlighted to point out future research possibilities.
• Evidence snippets:
• Snippet 1 (score: 0.542) > Osteosarcoma is the most common primary malignant osseous tumor accounting for the largest proportion (60%) of orthopedic malignant tumors that commonly affect children and those younger than 20 years (1,2). Distal femur and proximal tibia are the most common sites of osteosarcoma burst. However, the pathogenesis of osteosarcoma remains unclear, and it is considered to be related to the combination of genetic susceptibility, virus infection, ionizing radiation, and chemical toxins (3). Clinically, the main manifestations are swelling, pain, and dysfunction of adjacent joints, which can aggravate pain and affect patients' sleep at night (4). Several studies demonstrate that 80% of patients with osteosarcoma have a local invasion or distant metastasis when diagnosed (5). The lung is the most common organ for tumor metastasis, accounting for 85% of cases, and 90% of patients with tumors die because of metastasis (6). Current therapeutic strategies for osteosarcoma include surgical resection, radiotherapy, chemotherapy, and immunotherapy with a five-year survival rate of 70% (7). The prognosis of osteosarcoma is still unoptimistic. Tumor cells are resistant to chemotherapeutic drugs. Drug resistance is a critical factor contributing to therapeutic failure and tumor recurrence. Therefore, extensive research on elucidating the mechanisms involved in osteosarcoma and identifying relative molecular targets as well as treatment methods is warranted. > Cell death is a fundamental biological process that pervasively takes place in all living organisms (8). Cancer cells evade quintessential immune surveillance-mediated cell death and then, due to overwhelming proliferation, eventually cause dysregulation in the body (9). The five widely accepted forms of cell death are necrosis, apoptosis, necroptosis, pyroptosis, and ferroptosis (8). Pressing engagement of unknown stimulation or toxic factors concerning the unit of life could trigger uncontrolled necrosis. Additional aforementioned types are accordingly ascribed to regulated cell death (RCD) (10).

[6] Identification of Gene as Predictive Biomarkers for the Occurrence and Recurrence of Osteosarcoma

• Authors: Yuanguo Luo, Bo Lv, Shao-Ya He, Kai-fang Zou, Kezhi Hu
• Year: 2021
• Venue: International Journal of General Medicine
• URL: https://www.semanticscholar.org/paper/2c176c693a7c18860d3d415bdda2d6406ee1b573
• DOI: 10.2147/IJGM.S312277
• PMID: 33994806
• PMCID: 8113014
• Citations: 2
• Summary: The Cox model results confirmed that the signals of ATF5, CHCHD8, and LOC286367 were robust, and it may be used in the diagnosis, treatment, and prognosis of osteosarcoma.
• Evidence snippets:
• Snippet 1 (score: 0.538) > International Journal of General Medicine 2021:14 WGCNA is a systems biology approach that describes correlation patterns between genes in transcriptome samples with soft threshold algorithms. 23 The results of GO and KEGG pathway enrichment analysis of the module genes led us to focus on the biological functions of autophagy and macrophage migration, as well as the HIF-1 signaling pathway and PI3K-Akt signaling pathway. Autophagy promotes the proliferation and development of osteosarcoma cells and resists tumor treatment. 30 utophagy may be involved in drug sensitivity or chemoresistance during osteosarcoma treatment. 31 acrophages are an important immune component in the osteosarcoma microenvironment. Macrophages are highly plastic and the inflammatory phenotype (M1) and antiinflammatory phenotype (M2) may play opposite roles in the progression of osteosarcoma. 32 Activation of the HIF-1 signaling pathway promotes osteosarcoma cell growth and is a promising therapeutic target. 33 Accumulating evidence suggests that the PI3K/Akt pathway is involved in cancer initiation and progression, such as tumorigenesis, apoptosis inhibition, proliferation and drug resistance. 34 o further identify the underlying molecular mechanisms of osteosarcoma recurrence, we performed enrichment analysis of the differentially expressed genes between recurrence and non-recurrence. We found multiple immune related pathways, neutrophil mediated immunity, neutrophil apoptotic process, and leukocyte homeostasis. They may be associated with metastasis and recurrence of osteosarcoma. 35 In addition to a large number of aberrant biological functions, FOXO could control the expression of genes involved in cell death and cell cycle arrest, exerting tumor suppressor activity. 36 Tumor suppressor p53 tumor cells have been reported to exert anticancer effects by inducing cell cycle arrest and apoptosis. 37 f the 13 coexpression modules we identified, module 1 was found to be strongly associated with osteosarcoma.

[7] Interfering with UBE2L3 expression targets regulation of MLKL to promote necroptosis inhibition of growth in osteosarcoma

• Authors: Xiwu Zhao, Guoqiang Shan, Deguo Xing, Hongwei Gao, Zhenggang Xiong et al.
• Year: 2025
• Venue: World Journal of Surgical Oncology
• URL: https://www.semanticscholar.org/paper/b34edeb4263d09ee26ffa4556fc2d310f13a0c11
• DOI: 10.1186/s12957-025-03715-3
• PMID: 39988669
• PMCID: 11849225
• Citations: 1
• Summary: Investigating the molecular mechanisms by which interfering with UBE2L3 expression promotes necroptosis and impacts the progression of osteosarcoma suggests that inhibiting the expression of UBE2L3 can suppress the growth of osteosarcoma.
• Evidence snippets:
• Snippet 1 (score: 0.532) > Osteosarcoma is a rare but serious malignant tumor that primarily occurs in the growth areas of bones and soft tissues. According to recent epidemiological data, approximately 1-2 per million people are diagnosed with osteosarcoma worldwide, with a higher prevalence among children and adolescents aged 10-25 years [1]. The incidence rate of osteosarcoma is slightly higher in males than females, with a male-to-female ratio of approximately 1.4:1 [2,3]. The aggressive nature and high susceptibility to metastasis are among the defining characteristics and major clinical challenges of osteosarcoma. If left untreated, osteosarcoma can cause localized pain, swelling, and pathological fractures due to tumorinduced bone destruction. As the disease progresses, tumor cells primarily metastasize to the lungs through the bloodstream, while lymph node and other bone metastases are less common. This propensity for distant metastasis, particularly to the lungs, contributes to the high lethality of osteosarcoma, with a 5-year survival rate of approximately 20-30% for metastatic disease [4,5]. > The pathogenesis of osteosarcoma is associated with necroptosis, a form of regulated cell death mediated by RIPK1, RIPK3, and MLKL. Necroptosis is distinct from apoptosis, as it involves the loss of cell membrane integrity and the release of cellular contents, often triggering inflammatory responses [6,7]. Recent studies suggest that osteosarcoma cells may undergo necroptosis under specific conditions when exposed to chemotherapy drugs or radiation therapy, primarily due to the accumulation of reactive oxygen species (ROS) and DNA damage [8,9]. Dysregulated activation of pathways such as p53 may also indirectly influence necroptosis by modulating oxidative stress responses [10,11]. Given the involvement of multiple signaling pathways in necroptosis regulation, further exploration of its molecular mechanisms in osteosarcoma may lead to innovative therapeutic strategies, enhancing the efficacy of conventional treatments and improving patient outcomes. MLKL is a key execution protein in the necroptosis pathway, playing a central role in cell death signal transduction.

[8] Identification of Key Genes and miRNAs Affecting Osteosarcoma Based on Bioinformatics

• Authors: Le Li, Xiaoxia Zhou, Wencan Zhang, Ran Zhao
• Year: 2022
• Venue: Disease Markers
• URL: https://www.semanticscholar.org/paper/ddde566df49e94e4df8fce9703cdf737d060bd5d
• DOI: 10.1155/2022/1015593
• PMID: 36438897
• PMCID: 9683959
• Citations: 1
• Summary: The enrichment analysis showed that the common DEGs of GSE70367 and GSE69470 were related with cell development, covalent chromatin modification, and histone modification and involve in the regulation of MAPK, mTOR, and AMPK pathways.
• Evidence snippets:
• Snippet 1 (score: 0.526) > Osteosarcoma is a frequent malignant bone disease in children and older patients, which is characterized with poor prognosis including physical disability and metastases [1,2]. Surgery excision, radiotherapy, and chemotherapy have been widely used for osteosarcoma treatment, which can effectively inhibit the development of the tumor progression in the early stage [3]. Nevertheless, considerable patients have been confirmed to be at the advanced stage in their first clinical diagnosis. Moreover, high metastasis rates of osteosarcoma also make the clinical intervention become tricky and then lead to treatment failure [4]. Although the survival times of the patients have been significantly prolonged with the modern medicine techniques, the treatment effect remains unsatisfactory for patients [5,6]. At present, some reports have focused on revealing the potential mechanism of osteosarcoma, which can provide valuable reference for the progression of medicine strategies [7,8]. At present, there have been many studies on the molecular mechanism of osteosarcoma, and several osteosarcoma-driving genes have been identified, such as TP53, RB1, and PTEN. There have also been targeted drugs for osteosarcoma, such as pazopanib, appatinib, cabotinib, and ivermex. However, these studies have not clearly explained the pathogenesis and metastasis of osteosarcoma. Therefore, it is urgent to further study the potential molecular mechanism of osteosarcoma cells, identify reliable molecular markers, and identify new drug targets. > Microarray analysis is a useful method which has been used for screening the key genes in diseases [9]. Recently, the academic and guiding value of bioinformatics methods on improving the clinical practice have been proven by numerous researches [10]. MicroRNA is a class of the short noncoding RNA with 18-20 nucleotides, which plays a great part in the cellular life activity [11]. The abnormal expression of miRNA is a biomarker event in multiple diseases, especially in caner. In osteosarcoma, many studies have indicated that miRNA can regulate the cellular phenotype to influence the progression of the tumor via intervening the expression of key proteins [12].

[9] Present Advances and Future Perspectives of Molecular Targeted Therapy for Osteosarcoma

• Authors: A. Shaikh, Fangfei Li, Min Li, Bing He, Xiaojuan He et al.
• Year: 2016
• Venue: International Journal of Molecular Sciences
• URL: https://www.semanticscholar.org/paper/b4b6c41cef2d5ecf6f28565228bbab80daf1445e
• DOI: 10.3390/ijms17040506
• PMID: 27058531
• PMCID: 4848962
• Citations: 121
• Summary: This review summarizes the current development of molecular mechanisms and targets for osteosarcoma and Therapies that target these mechanisms with updated information on clinical trials are reviewed.
• Evidence snippets:
• Snippet 1 (score: 0.515) > Osteosarcoma (OS) is a primary bone cancer, predominantly affecting children and adolescence population [1]. OS originates from primitive mesenchymal bone forming cells and often occurs in long bones, such as proximal tibia and distal femur [2,3]. Current OS treatment regime consists of the combination of surgery and intensive multi-agent chemotherapy. Ever since the introduction of chemotherapy, five-year survival rate among OS patients has improved to 60%-75% [4]. However, 30%-40% of OS patients are associated with pulmonary metastasis and relapse, which have significantly poor prognosis, with an overall five-year survival rate of about 20% [5]. Moreover, over the past few decades, no substantial improvement in survival rate has been achieved, though efforts were made by intensifying dosing, varying timing and using multi-combinational chemotherapy. Additionally, several adverse effects are accompanied by high-dose chemotherapy [6]. Hence, there is an increasing sense of urgency to identify new biological markers and develop novel, innovative and specific molecular targeted therapeutic approaches to improve the outcome in osteosarcoma patients with poor prognosis. In this review, we will discuss about molecular mechanism underlying osteosarcoma, current molecular therapeutic targets against immune system, extracellular and Intercellular signaling transduction pathway of the bone metabolism, as well as novel therapeutic targets and drug delivery systems that have been investigated or are currently undergoing investigation in translational studies (Figure 1). > is an increasing sense of urgency to identify new biological markers and develop novel, innovative and specific molecular targeted therapeutic approaches to improve the outcome in osteosarcoma patients with poor prognosis. In this review, we will discuss about molecular mechanism underlying osteosarcoma, current molecular therapeutic targets against immune system, extracellular and Intercellular signaling transduction pathway of the bone metabolism, as well as novel therapeutic targets and drug delivery systems that have been investigated or are currently undergoing investigation in translational studies (Figure 1).

[10] Osteosarcoma: From Molecular Biology to Mesenchymal Stem Cells

• Authors: M. Broadhead, Saumiyar Sivaji, Z. Balogh, P. Choong
• Year: 2017
• Venue: Unknown venue
• URL: https://www.semanticscholar.org/paper/fd25c72bc7c0f5742654c8167d9cbc956afbc2d3
• DOI: 10.5772/67371
• Citations: 5
• Influential citations: 1
• Summary: This work has shown that interactions of MSCs with osteosarcoma cells in the tumour microenvironment may cause increased cell proliferation, in stark contrast to the role of M SCs as a promising source for tissue repair and regeneration.
• Evidence snippets:
• Snippet 1 (score: 0.510) > The pathogenesis of osteosarcoma is a complex process, which is not completely understood and involves tumorigenesis from mesenchymal cells, alterations in cellular apoptosis, adhesion, migration and invasion, as well as tumour-induced osteolysis and angiogenesis.Various genetic and molecular alterations underlie these processes.It is hoped that by targeting the deranged molecular signalling of these pathways that novel treatment agents could be developed that enhance the efficacy of conventional chemotherapeutics and possibly reduce patient morbidity.

[11] Molecular pathogenesis and therapeutic strategies of human osteosarcoma

• Authors: S. Denduluri, Zhongliang Wang, Zhengjian Yan, Jing Wang, Q. Wei et al.
• Year: 2015
• Venue: Journal of Biomedical Research
• URL: https://www.semanticscholar.org/paper/c3a438369c1d4c03e198761da58e1b294e2c3f98
• DOI: 10.7555/JBR.30.20150075
• PMID: 26496981
• PMCID: 4726829
• Citations: 42
• Influential citations: 3
• Summary: Current understanding of OS disease processes is summarized and light is shed on the multitude of potential therapeutic strategies the scientific community can use to make long-term improvements in patient prognosis.
• Evidence snippets:
• Snippet 1 (score: 0.509) > Abstract Osteosarcoma (OS) is a devastating illness with rapid rates of dissemination and a poor overall prognosis, despite aggressive standard-of-care surgical techniques and combination chemotherapy regimens. Identifying the molecular mechanisms involved in disease pathogenesis and progression may offer insight into new therapeutic targets. Defects in mesenchymal stem cell differentiation, abnormal expression of oncogenes and tumor suppressors, and dysregulation within various important signaling pathways have all been implicated in development of various disease phenotypes. As such, a variety of basic science and translational studies have shown promise in identifying novel markers and modulators of these disease-specific aberrancies. Born out of these and similar investigations, a variety of emerging therapies are now undergoing various phases of OS clinical testing. They broadly include angiogenesis inhibitors, drugs that act on the bone microenvironment, receptor tyrosine kinase inhibitors, immune system modulators, and other radio- or chemo-sensitizing agents. As new forms of drug delivery are being developed simultaneously, the possibility of targeting tumors locally while minimizing systemic toxicityis is seemingly more achievable now than ever. In this review, we not only summarize our current understanding of OS disease processes, but also shed light on the multitude of potential therapeutic strategies the scientific community can use to make long-term improvements in patient prognosis.

[12] Functional role of MicroRNA/PI3K/AKT axis in osteosarcoma

• Authors: Yubo Xiang, Yingxin Yang, Jia Liu, Xu Yang
• Year: 2023
• Venue: Frontiers in Oncology
• URL: https://www.semanticscholar.org/paper/7ee4005d3ffedc8e55a01bbc619244b5583a3a1d
• DOI: 10.3389/fonc.2023.1219211
• PMID: 37404761
• PMCID: 10315918
• Citations: 22
• Summary: This article reviews recent research advances on the role and clinical application of PI3K/AKT pathway and miRNA/PI3K /AKT axis in the development of osteosarcoma and identifies potential biomarkers for osteosARcoma diagnosis, treatment and prognostic assessment.
• Evidence snippets:
• Snippet 1 (score: 0.505) > Osteosarcoma (OS) is a primary malignant bone tumor derived from bone forming mesenchymal stem cells. It is highly malignant and can be locally aggressive and often leading to pulmonary or even systemic metastases. Children and adolescents are the most common patients with osteosarcoma, second only to lymphoma and brain tumors in the childhood and adolescent population (1)(2)(3). The distal end of the femur is the most common site for osteosarcoma, followed by the proximal end of the tibia and humerus (2,(4)(5)(6). Local invasion is observed in more than 85% of osteosarcoma patients, with lung metastases being the most common in 74% of patients with metastases, followed by bone metastases in 9% of patients, and both bone and lung metastases in 8% of patients with metastases (6). In recent decades, surgery combined with new chemotherapy has been recognized as the standard treatment for osteosarcoma, significantly improving overall survival and quality of life (7). Emerging chemotherapy regimens include cisplatin (DDP), a d r i a m y c i n ( D O X ) , m e t h o t r e x a t e ( M T X ) , a n d isocyclophosphamide (IFO) (7). However, the therapeutic effect of chemotherapeutic agents is limited by various reasons, such as escape of apoptosis, reduced drug uptake, and increased drug metabolism. Systemic metastasis limits the effectiveness of surgical resection, so metastatic and drug resistance often result in unsatisfactory outcomes and prognosis for patients with osteosarcoma (8). The problems described above involve changes in multiple biological processes, including changes in genetic and epigenetic characteristics. Understanding and studying the molecular changes of genes associated with the formation of osteosarcoma and associated signaling pathways will help uncover the mechanisms underlying its occurrence and development, providing new directions for the diagnosis, targeted therapy, and prognosis of osteosarcoma.

[13] Global research trends and hotspots in metabolomics of osteosarcoma: a decade-spanning bibliometric and visualized analysis

• Authors: Jun-Bo Tu, Tao Liu, Jun-Feng Li, Jianglan Long, Xiu Q Wang et al.
• Year: 2024
• Venue: Frontiers in Immunology
• URL: https://www.semanticscholar.org/paper/b263dfc2df6e9cb7d76c55bf4fa3a27761b9a900
• DOI: 10.3389/fimmu.2024.1463078
• PMID: 39445018
• PMCID: 11496093
• Citations: 3
• Summary: The evolution and convergence of research themes in osteosarcoma metabolomics over the past decade is delineated, major contributors are identified, and forecast emerging trends that could direct future research efforts are forecast.
• Evidence snippets:
• Snippet 1 (score: 0.505) > The molecular mechanisms related to osteosarcoma metabolism mainly involve signal transduction pathways, gene expression regulation, and cell proliferation and apoptosis mechanisms. Research mainly focuses on the occurrence, development and treatment response mechanisms of osteosarcoma, especially the key molecules and pathways that lead to tumor growth and metastasis. Autophagy is an important process that maintains cellular homeostasis. This process is complex and involves the removal of damaged proteins and organelles. In osteosarcoma, autophagy may play a dual role, that is, it can induce cell death and maintain the survival of tumor cells. Understanding molecular mechanisms and autophagy can provide insights into the mechanisms of cancer and can also help develop new treatment strategies. For example, the cancer-promoting protein IF1 helps tumor cell growth by promoting mitochondrial renewal and energy conservation (64). Sergio Almansa-Gomez, Francisco Prieto-Ruiz and others made a review on the regulation of autophagy in osteosarcoma. They believed that many results have been achieved in the regulation of autophagy in osteosarcoma in the past, but future research still needs to elucidate the role of autophagy. Molecular mechanisms and their relationship to osteosarcoma (65).

[14] Targeting the mammalian target of rapamycin pathway in osteosarcoma using combinative chemotherapy

• Authors: Pei‐yi Liu, Wei-bin Zhang, Yili Wei
• Year: 2013
• Venue: Chinese Medical Journal
• URL: https://www.semanticscholar.org/paper/854effcfc78c7297b3e5b92fa3221faa97a09db7
• DOI: 10.3760/cma.j.issn.0366-6999.20112107
• PMID: 23673121
• Citations: 1
• Summary: Although multiple chemotherapy regimens have improved the outcome of patients with osteosarcoma, resistance to current regimens has been reported in more than 30% of patients, highlighting the need for novel, targeted therapies.
• Evidence snippets:
• Snippet 1 (score: 0.500) > Osteosarcoma is a highly aggressive tumor with a higher rate of metastasis than most cancers in children and young adults. The prognosis of patients with osteosarcoma is associated with response to chemotherapy; however osteosarcoma is highly resistant to current treatment regimens. Understanding the molecular mechanisms underlying the development and malignant behavior of osteosarcoma is crucial for developing targeted therapeutic approaches and for the identification of novel chemotherapy agents.

[15] Down‐regulation of PDGFRβ suppresses invasion and migration in osteosarcoma cells by influencing epithelial–mesenchymal transition

• Authors: Si-Ning Xing, Changdong Wang, Huying Tang, Jiaying Guo, Xing Liu et al.
• Year: 2020
• Venue: FEBS Open Bio
• URL: https://www.semanticscholar.org/paper/5214c55fa1a798f04d89ee469558eb977d13c8b1
• DOI: 10.1002/2211-5463.12915
• PMID: 32580247
• PMCID: 7459394
• Citations: 13
• Summary: It is suggested that PDGFRβ plays an important role in OS invasion, migration and epithelial–mesenchymal transition by influencing the PI3K, Akt and mTOR pathways, hence highlighting PDG FRβ as a potential therapeutic target for OS.
• Evidence snippets:
• Snippet 1 (score: 0.500) > As a cancerous tumor that originates from bone, osteosarcoma (OS) is the most frequent histological type of primary bone cancer and is becoming the second leading cause of cancer-related deaths in children and adolescents [1]. It accounts for ~20% of all primary bone cancers and 2.4% of all malignancies, with high mortality and morbidity in children [2]. Tumor metastasis, especially lung metastasis, is the main reason for the death of patients with OS [3]. Approximately one-fifth of the patients have micrometastasis in the lungs when OS is diagnosed. Surgery is an important way to treat this disease, but the subsequent complications may result in more serious consequences [4]. A variety of agents have been investigated for the treatment of OS in clinical trials. Although several studies focus on the molecular mechanism of OS, the specific mechanism remains unclear. Further research on OS pathogenesis may provide new ideas for the treatment of OS. With the discovery of an increasing number of molecular mechanisms that can mediate the invasion and metastasis of OS, epithelial-mesenchymal transition (EMT) has aroused interest [5][6][7]. EMT is one of the transformations by which tumor cells can acquire the ability to migrate and is an important process in tumor cell infiltration and metastasis [8,9]. It has been reported that EMT is highly correlated with the invasive and metastatic performances of many types of tumor cells [10,11] and especially promotes the metastasis of epithelial neoplasms [12]. EMT also plays a pivotal position in primary and secondary metastases in OS [13]. > Receptor tyrosine kinases (RTKs) are key players in the regulation of numerous fundamental cellular processes, such as growth, migration and apoptosis, and are involved in tumorigenesis, disease progression and metastatic spread of numerous human cancers [14][15][16][17]. Platelet-derived growth factor receptor (PDGFR) belongs to the family of type III tyrosine protein kinases, and PDGFR beta (PDGFRβ) is an important subtype of PDGFR.

[16] Integrated gene network analysis sheds light on understanding the progression of Osteosarcoma

• Authors: Hrituraj Dey, K. Vasudevan, G. Doss C., S. U. Kumar, A. El Allali et al.
• Year: 2023
• Venue: Frontiers in Medicine
• URL: https://www.semanticscholar.org/paper/2dbcc0c2f0f8379bdf5b389aa75d140c1a1b975b
• DOI: 10.3389/fmed.2023.1154417
• PMID: 37081847
• PMCID: 10110863
• Citations: 6
• Summary: This study aims to highlight the hub genes involved in gene-gene interaction network to understand their interaction and how they affect the various biological processes and signaling pathways involved in Osteosarcoma and highlights the candidate hub genes viz.
• Evidence snippets:
• Snippet 1 (score: 0.500) > A cancer cell will essentially have six hallmark capabilities to be recognized as a cancer cell. The six core hallmarks outlined by Hananah and Weinberg include self-sufficiency in growth signals, insensitivity to antigrowth signals, evasion of programmed cell death (apoptosis), limitless replicative potential, sustained angiogenesis, and tissue invasion and metastasis, along with the emerging hallmarks of cancer which includes deregulating cellular energetics and avoiding immune destruction (24, 25). Attaining each capability will likely involve inactivating or eluding a specific control mechanism. We have utilized a gene interaction network in our study to understand the development and progression of the tumor cells in Osteosarcoma. This helped us decipher a group of highly interactive genes responsible for the pathogenesis and spread of the disease. > During analysis, MF observed were kinase binding, kinase regulator activity, and transcription factor activity. Prior studies on Osteosarcoma have highlighted that protein tyrosine kinases are essential signaling molecules involved in the signaling pathways that regulate cellular differentiation and proliferation (26). The enriched BPs of Osteosarcoma included signal transduction, cell communication, regulation of cell cycle, regulation of nucleobase, nucleoside, nucleotide and nucleic acid metabolism, apoptosis, protein metabolism, energy pathways, metabolism along with cell cycle checkpoint signaling, DNA damage checkpoint signaling, and response to hypoxia. Earlier studies have shown that impairment in signal transduction, cell communication, and cell cycle checkpoint signaling has significantly promoted Osteosarcoma (27). Signal transduction is a sequential event where an extracellular signal is transduced by the cell to create a response, which is necessary for the normal growth and development of the cell. Since genetic alterations drive cancer, these alterations create a wide range of aberrant signaling networks that drives the expansion of the tumor. These signaling pathways control tumor growth, development, and fate (28). The signal transduction pathway involved 14 genes namely CCND1, CDK4, VEGFA, CDKN2A, SRC, CHEK2, ERBB2, CD44, CCNE1, PLK1, CDC6, AURKA, CCNB2, and TNFSF11.

[17] Mesenchymal Stem Cells and Extracellular Vesicles in Osteosarcoma Pathogenesis and Therapy

• Authors: V. Sarhadi, Ravindra Daddali, R. Seppänen-Kaijansinkko
• Year: 2021
• Venue: International Journal of Molecular Sciences
• URL: https://www.semanticscholar.org/paper/6983a860b85ab0a97b3c53018b39acfd16a09b35
• DOI: 10.3390/ijms222011035
• PMID: 34681692
• PMCID: 8537935
• Citations: 51
• Influential citations: 1
• Summary: The role of MSC-EVs is highlighted, with a focus on EV-mediated communication between OS cells and MSCs and their role in OS pathogenesis and therapy, to highlight the high heterogeneity and genetic complexity of OS.
• Evidence snippets:
• Snippet 1 (score: 0.495) > Osteosarcoma (OS) is the most predominant primary bone cancer, commonly occurring in the long bones of children and adolescents [1]. OS is highly malignant and the major complications in OS arise due to a lack of immune response, leading to irregular bone growth and distant metastases, seen commonly in the lungs and liver. The current treatment approaches for OS are preoperative chemotherapy, surgical resection, and postoperative chemotherapy, which are effective in patients with localized OS. Conversely, patients with advanced, metastatic, and recurrent OS develop resistance to chemotherapy, which makes it difficult to treat, resulting in a poor prognosis [2]. Despite multidisciplinary treatments, there has been no change in the prognosis during the past two decades. The overall 5-year survival rate of OS patients is 65% in the case of localized disease, while it is 20% in those with metastasis, and significantly lower in those with lung metastasis [3]. The high heterogeneity and genetic complexity of OS make it challenging to identify new therapeutic targets [4]. > A thorough understanding of the tumor microenvironment (TME), especially the bone microenvironment (BME), cellular crosstalk, and the molecular mechanisms underlying tumor progression, is essential for drug design and for developing new drug molecules for OS treatment. The BME is composed of the extracellular matrix (ECM) and a variety of cells, which includes mesenchymal stem cells (MSCs), endothelial cells, macrophages, stem cells, fibroblasts, osteoblasts, osteoclasts, and osteocytes that are organized to maintain the bone rigidity and the structural as well as functional integrity of the bone niche. All these cells together play a crucial role in normal bone development and bone physiology and can also lead to osteosarcoma in aberrant conditions. > MSCs are multipotent, non-hematopoietic cells that have the potential to self-rejuvenate and to differentiate into different cell types, including muscle cells, hepatocytes, osteoblasts, adipocytes, chondrocytes, and stromal cells [5,6].

[18] Involvement of TP53 in osteosarcoma - challenges and prospects

• Authors: Yue Shen, Shuzhou Huang, Geng Chen, Guangda Wang, L. Sui
• Year: 2025
• Venue: Frontiers in Oncology
• URL: https://www.semanticscholar.org/paper/f4de5949ca03e6677f6b90cc0b23d966a37a92dc
• DOI: 10.3389/fonc.2025.1605080
• PMID: 41323391
• PMCID: 12657174
• Citations: 3
• Summary: This review provides an in-depth analysis of p53 biology in OS, highlighting its impact on therapeutic resistance and tumor progression and underscores opportunities for translational research aimed at improving the clinical outcomes of OS patients.
• Evidence snippets:
• Snippet 1 (score: 0.494) > The pivotal role of p53 dysregulation in osteosarcoma pathogenesis and therapeutic resistance is now well-established. Mutant p53 proteins, particularly those with gain-of-function mutations, contribute significantly to disease progression and are present in over 50% of osteosarcoma cases. These mutations are categorized into structural and contact types based on their distinct mechanisms of disrupting p53 function, with structural mutations frequently involving non-random intronic breakpoints that may confer selective advantages during tumor evolution. The precise characterization of these genetic alterations provides not only insights into tumor biology but also critical opportunities for clinical translation. > From a diagnostic perspective, the recurrent identification of specific mutant alleles in patients experiencing sequential relapsesas well as in experimentally validated drug-resistant models-offers a strong rationale for developing mutation-specific prognostic biomarkers and targeted therapeutic strategies. These findings are particularly relevant for overcoming methotrexate resistance, a major clinical challenge in osteosarcoma management. The translation of these molecular insights into clinically applicable tools represents a promising direction for personalized treatment approaches. > Therapeutically, significant progress has been made in developing agents that target p53 pathways, including novel MDM2 inhibitors and p53-stabilizing compounds, several of which are currently in preclinical and early clinical development. Beyond conventional chemotherapy, contemporary research emphasizes combinatorial strategies that address resistance mechanisms through immunomodulation, metabolic targeting, and stem cell pathway inhibition. Emerging approaches such as mutation-specific promoter editing, enhancer reprogramming, and functional genetic screens offer additional avenues for identifying therapeutic vulnerabilities. Collectively, these advances are shaping a new paradigm of precision medicine in osteosarcoma, providing hope for improved outcomes through biologically rational and individualized treatment strategies.

[19] Upregulation of 15 Antisense Long Non-Coding RNAs in Osteosarcoma

• Authors: Emel Rothzerg, X. D. Ho, Jiake Xu, D. Wood, A. Märtson et al.
• Year: 2021
• Venue: Genes
• URL: https://www.semanticscholar.org/paper/85ee116d09d4cb8c4cbb748ce325a97bbc981099
• DOI: 10.3390/genes12081132
• PMID: 34440306
• PMCID: 8394133
• Citations: 36
• Summary: This study investigated the expression patterns of antisense lncRNAs from osteosarcoma and healthy bone samples using RNA sequencing and identified 15 that were upregulated in tumour samples compared to bone sample controls.
• Evidence snippets:
• Snippet 1 (score: 0.490) > Osteosarcoma (OS), also known as osteogenic sarcoma, is the most common primary malignant solid tumour of bone [1]. The peak incidence is in children and adolescents with a smaller second peak in incidence after the age of 65 years associated with Paget's disease of bone [2]. OS commonly develops in the extremities of long bones such as the distal femur, proximal tibia, proximal humerus, and proximal femur [3]. It is an aggressive-invasion sarcoma type that frequently metastasizes to the lung and other bones in the body [4]. OS usually presents with pain, tenderness and swelling around the affected bone, and diagnosis is achieved by a combination of imaging and histology with the characteristic appearance of malignant cells forming osteoid [5]. Cytotoxic chemotherapy was introduced by Rosen in the 1970s and improved the prognosis from 20% to a 70% five-year survival rate with no further significant improvements in outcome since then [6]. Current treatments of OS include neo-adjuvant chemotherapy with drugs such as doxorubicin, methotrexate, and cisplatin with the aim of reducing tumour size as well as eradicating micro-metastases. Ablative surgery is then followed by further chemotherapy determined by the cell death rate observed in the surgical specimens [7,8]. Current OS therapeutic agents are limited to cytotoxic drugs interfering with transcription and DNA replication [6]. This is a reflection of our knowledge of the pathways involved in OS initiation and progression, which are insufficient to understand the underlying molecular mechanisms of the disease. > The sense strand of DNA provides the template for production of messenger RNA (mRNA) to be translated into proteins [9], but the Human Genome Project highlighted that only 1.5% of the human genome contains protein-coding genes. In addition, the Encyclopedia of DNA elements (ENCODE) and the Functional Annotation of the Mammalian Genome (FANTOM) have suggested that the majority of the genome is transcribed and produces a various amount of non-coding RNA species (ncRNAs) [10,11].

[20] The Molecular Pathogenesis of Osteosarcoma: A Review

• Authors: M. Broadhead, Jonathan C. M. Clark, D. Myers, C. Dass, P. Choong
• Year: 2011
• Venue: Sarcoma
• URL: https://www.semanticscholar.org/paper/9d7784947e608548778f2eeb255836884b6829ce
• DOI: 10.1155/2011/959248
• PMID: 21559216
• PMCID: 3087974
• Citations: 357
• Influential citations: 12
• Summary: The pathogenic mechanisms of osteosarcoma oncogenesis and progression are outlined and some of the more frontline translational studies performed to date in search of novel, safer, and more targeted drugs for disease management are discussed.
• Evidence snippets:
• Snippet 1 (score: 0.485) > Osteosarcoma is the most common primary malignancy of bone. It arises in bone during periods of rapid growth and primarily affects adolescents and young adults. The 5-year survival rate for osteosarcoma is 60%–70%, with no significant improvements in prognosis since the advent of multiagent chemotherapy. Diagnosis, staging, and surgical management of osteosarcoma remain focused on our anatomical understanding of the disease. As our knowledge of the molecular pathogenesis of osteosarcoma expands, potential therapeutic targets are being identified. A comprehensive understanding of these mechanisms is essential if we are to improve the prognosis of patients with osteosarcoma through tumour-targeted therapies. This paper will outline the pathogenic mechanisms of osteosarcoma oncogenesis and progression and will discuss some of the more frontline translational studies performed to date in search of novel, safer, and more targeted drugs for disease management.

Notes

• This provider combines search_papers_by_relevance with snippet_search.
• No synthesis or second-stage model call is performed.

Disorder

• Name: Osteosarcoma
• Category: Cancer
• Existing deep-research providers: falcon, perplexity
• Existing evidence reference count in YAML: 33

Key Pathophysiology Nodes

• Malignant Bone-Forming Tumor
• Tumor Immune Microenvironment Remodeling
• PI3K/Akt Pathway Hyperactivation
• Deep research literature mapping

Citation Inventory (for evidence mapping)

• DOI:10.1002/pdi3.18
• DOI:10.1007/s00432-024-05787-2
• DOI:10.1038/s41413-022-00237-6
• DOI:10.1073/pnas.0805462105
• DOI:10.1200/jco.2025.43.16_suppl.10045
• DOI:10.3389/fcell.2021.645381
• DOI:10.3389/fcell.2021.737314
• DOI:10.3389/fcell.2023.1123065
• DOI:10.3389/fimmu.2025.1579822
• DOI:10.3389/fimmu.2025.1584450
• DOI:10.3389/fonc.2020.00406
• DOI:10.3389/fonc.2020.563255
• DOI:10.3389/fonc.2023.1117867
• DOI:10.3389/fphar.2024.1350187
• DOI:10.3389/fphar.2024.1459057
• DOI:10.3389/fpubh.2021.813625
• DOI:10.3390/biom14020145
• DOI:10.3390/ijms241310463
• DOI:10.3390/ijms241411367
• DOI:10.3892/ijmm.2025.5533
• PMID:15736406
• PMID:25704303
• PMID:278229
• PMID:28370561
• PMID:289343
• PMID:39615111
• PMID:8781571

Pathophysiology description Osteosarcoma (OS) is a high-grade primary malignant bone tumor characterized by profound genomic instability, dysregulated developmental and stress-response signaling, metabolic rewiring, and a uniquely immunosuppressive bone tumor microenvironment (TME) that collectively drive invasion, lung metastasis, and treatment resistance (nirala2023decipheringthesignaling pages 1-2). Genomic catastrophe is a defining feature: chromothripsis and kataegis co-occur with frequent loss of key tumor suppressors (TP53, RB1, ATRX) and gains of oncogenes (MYC, MDM2), with epigenetic dysregulation superimposed on widespread copy-number alterations (nirala2023decipheringthesignaling pages 1-2, pires2023analysisofthe pages 2-5, alansari2024unveilingtheprotective pages 6-8). Convergent activation of PI3K/AKT/mTOR, Wnt/β‑catenin, TGF‑β, JAK/STAT, NOTCH, Hedgehog/GLI, RANK/RANKL, and NF‑κB pathways promotes proliferation, survival, EMT-like migration, osteoclastogenic crosstalk, and metastasis (nirala2023decipheringthesignaling pages 2-4). Single-cell analyses reveal immune-evasion programs including downregulation of MHC-I/B2M and upregulation of PD‑L1 and the anti-phagocytic ligand CD24 on cancer cells, accompanied by expansion of immunoregulatory LAMP3+CCR7+CD83+ dendritic cells (mregDCs) and SPP1+ tumor-associated macrophages (TAMs) (liu2023characterizingthetumor pages 2-3). Neoadjuvant chemotherapy remodels this ecosystem toward stemness-enriched tumor cells, ECM‑remodeling CAFs, altered endothelium, and depletion of effector myeloid and T/NK compartments, contributing to resistance and relapse (zheng2024singlecelltranscriptomicinsights pages 1-2).

Key concepts and definitions (current understanding) - Chromothripsis: catastrophic one-off chromosome shattering and rejoining that accelerates karyotype evolution; prevalent in OS and linked to micronuclei and decatenation defects (quote: mechanisms include “micronuclear DNA damage”; RanGAP1 reduction increases chromothripsis risk) (nirala2023decipheringthesignaling pages 2-4). URL: https://doi.org/10.3390/ijms241411367 (Jul 2023). - Kataegis: localized hypermutation tracts; reported in roughly half of OS and often co‑occurs with chromothripsis (nirala2023decipheringthesignaling pages 2-4, pires2023analysisofthe pages 2-5, alansari2024unveilingtheprotective pages 6-8). URLs: https://doi.org/10.3390/ijms241411367 (Jul 2023); https://doi.org/10.3390/ijms241310463 (Jun 2023); https://doi.org/10.3390/biom14020145 (Jan 2024). - mregDCs: LAMP3+CCR7+CD83+ mature regulatory dendritic cells enriched in OS tumors; associated with Treg recruitment and poorer survival; increasing inhibitory ligands (PD‑L1, LAG3, LGALS9, SIRPA, TIGIT, PD‑L2) along DC maturation trajectories (liu2023characterizingthetumor pages 2-3). URL: https://doi.org/10.1038/s41413-022-00237-6 (Jan 2023). - SPP1+ TAMs: osteopontin-expressing macrophages linked to immune suppression and adverse prognosis in OS ecosystems (liu2023characterizingthetumor pages 2-3). URL: https://doi.org/10.1038/s41413-022-00237-6 (Jan 2023).

Recent developments and latest research (2023–2024 priority) - Genomic landscape in new primary OS: 28-tumor cohort delineated 445 deleterious coding variants with recurrent TP53 (~60% considering SNV/indel/CNA), RB1, ATRX, and complex CNA patterns reminiscent of chromothripsis/chromoanasynthesis; pathway enrichment implicated immunity and bone development programs (pires2023analysisofthe pages 2-5). URL: https://doi.org/10.3390/ijms241310463 (Jun 2023). - Single-cell TME remodeling after chemotherapy: residual cells upregulate stemness; CAFs expand and increase ECM-remodeling capacity; endothelial cells increase with impaired differentiation; anti-tumor myeloid and T/NK subsets are depleted (zheng2024singlecelltranscriptomicinsights pages 1-2). URL: https://doi.org/10.1007/s00432-024-05787-2 (Jul 2024). - Single-cell immune evasion mechanisms: inferCNV-linked CNV‑high cancer cells downregulate interferon pathways and MHC-I/B2M; mregDCs correlate with Tregs; CD24 identified as a “don’t eat me” signal on OS cells (liu2023characterizingthetumor pages 2-3). URL: https://doi.org/10.1038/s41413-022-00237-6 (Jan 2023).

Current applications and real-world implementations - Molecular risk and target identification: Copy-number and expression assessment of TP53/RB1 loss, MDM2 gain, and MYC amplification inform prognosis and experimental targeting (e.g., MDM2–p53 axis) (pires2023analysisofthe pages 2-5, nirala2023decipheringthesignaling pages 1-2). URL: https://doi.org/10.3390/ijms241310463 (Jun 2023); https://doi.org/10.3390/ijms241411367 (Jul 2023). - Immune profiling for trial design: scRNA-seq-defined mregDC and SPP1+ TAM signatures, MHC-I/B2M loss, and PD‑L1 expression guide rational immunotherapy combinations (checkpoint blockade + myeloid/DC modulation) (liu2023characterizingthetumor pages 2-3). URL: https://doi.org/10.1038/s41413-022-00237-6 (Jan 2023). - Therapy sequencing considerations: Post-chemotherapy scRNA-seq suggests combining cytotoxic therapy with CAF/ECM-targeting or immune-restoring agents to mitigate stemness/ECM/immune escape (zheng2024singlecelltranscriptomicinsights pages 1-2). URL: https://doi.org/10.1007/s00432-024-05787-2 (Jul 2024).

Expert opinions and analysis (authoritative sources) - 2023 signaling review emphasizes the convergence of PI3K/AKT/mTOR, Wnt/β‑catenin, TGF‑β, JAK/STAT, NOTCH, Hedgehog, RANK/RANKL, and NF‑κB as drivers of proliferation, invasion, and lung metastasis; also highlights chromothripsis/kataegis as frequent, and immune–tumor crosstalk as clinically relevant (nirala2023decipheringthesignaling pages 2-4, nirala2023decipheringthesignaling pages 1-2). URL: https://doi.org/10.3390/ijms241411367 (Jul 2023). - 2023 mutational landscape study concludes “high genomic OS instability and heterogeneity,” identifying novel disrupted genes linked to poor outcomes and reinforcing TP53/RB1 centrality (pires2023analysisofthe pages 2-5). URL: https://doi.org/10.3390/ijms241310463 (Jun 2023). - 2023 single-cell atlas authors state that mregDCs “promote tumor immune tolerance through recruitment of Tregs” and that CNV‑high tumor cells exhibit “reduced interferon‑γ pathway activity and lower MHC‑I/B2M” (liu2023characterizingthetumor pages 2-3). URL: https://doi.org/10.1038/s41413-022-00237-6 (Jan 2023).

Relevant statistics and data (recent studies) - Genomic burden: 74,880 SNVs/indels across 28 primaries; filtered 445 coding non-synonymous candidates; TP53 alterations ~60% including SNV/indel/CNA; frequent gains 1q21, 6p21, 8q; losses 10q26, 13q14–21; complex CNA patterns (pires2023analysisofthe pages 2-5). URL: https://doi.org/10.3390/ijms241310463 (Jun 2023). - scRNA-seq TME composition (pre-therapy OS): myeloid ~35%, tumor ~27%, plus T/ILC, B cells, osteoclasts, endothelial, mesenchymal stromal cells (zheng2024singlecelltranscriptomicinsights pages 1-2). URL: https://doi.org/10.1007/s00432-024-05787-2 (Jul 2024).

Structured knowledge base annotations - Genes/Proteins (HGNC): TP53, RB1, ATRX, MYC, MDM2, PIK3CA, AKT1, MTOR, CTNNB1, TGFBR2, JAK2, NOTCH1, SMO, NFKB1, SPP1, CD274 (PD‑L1), B2M, HLA‑A/B/E, CD24 (nirala2023decipheringthesignaling pages 2-4, pires2023analysisofthe pages 2-5, liu2023characterizingthetumor pages 2-3). - Biological processes (GO): DNA damage response; chromatin organization; mitotic cell cycle; signal transduction via PI3K/AKT/mTOR; Wnt signaling; TGF‑β signaling; JAK/STAT cascade; NOTCH signaling; Hedgehog signaling; NF‑κB signaling; osteoclast differentiation (RANK/RANKL); antigen processing and presentation via MHC class I; regulation of macrophage activation; extracellular matrix organization; glycolytic process; glutamine metabolic process; fatty acid metabolic process (nirala2023decipheringthesignaling pages 2-4, pires2023analysisofthe pages 2-5, liu2023characterizingthetumor pages 2-3, zheng2024singlecelltranscriptomicinsights pages 1-2). - Cellular components: micronuclei (chromothripsis mechanism); nucleus/chromatin; plasma membrane (PD‑L1, CD24); MHC-I complex; extracellular matrix; exocytic vesicles; endothelium; osteoclastic resorption lacunae (nirala2023decipheringthesignaling pages 2-4, liu2023characterizingthetumor pages 2-3, zheng2024singlecelltranscriptomicinsights pages 1-2). - Cell types (CL): osteoblast-like tumor cell; mesenchymal stromal cell; cancer-associated fibroblast; SPP1+ tumor-associated macrophage; mature regulatory dendritic cell (LAMP3+CCR7+CD83+); osteoclast; endothelial cell; T cell and NK cell (liu2023characterizingthetumor pages 2-3, zheng2024singlecelltranscriptomicinsights pages 1-2). - Anatomical locations (UBERON): bone (primary); lung (metastatic); bone marrow niche; perivascular/endosteal/hypoxic niches (nirala2023decipheringthesignaling pages 1-2, alansari2024unveilingtheprotective pages 6-8). - Chemical entities (ChEBI): lactate (glycolysis), glutamine, fatty acids; cisplatin context for chemosensitivity; growth factors such as TGF‑β; cytokines/chemokines influencing niches (zheng2024singlecelltranscriptomicinsights pages 1-2, nirala2023decipheringthesignaling pages 2-4, alansari2024unveilingtheprotective pages 6-8).

Evidence items with PMIDs/DOIs, key mechanistic quotes - Nirala 2023 (IJMS; Jul 2023): “Massive genomic rearrangement (chromothripsis) is highly prevalent in OS… loss/reduction of RanGAP1 increases chromothripsis risk… Alterations in PI3K/AKT/mTOR, JAK/STAT, Wnt/β‑catenin, NOTCH, Hedgehog/Gli, TGF‑β, RTKs, RANK/RANKL, and NF‑κB have been identified in OS development and metastasis.” DOI: 10.3390/ijms241411367. https://doi.org/10.3390/ijms241411367 (nirala2023decipheringthesignaling pages 2-4, nirala2023decipheringthesignaling pages 1-2). - Pires 2023 (IJMS; Jun 2023): “TP53 was the most recurrently mutated gene, with an overall rate of ~60%… Seven cases presented CNA patterns reminiscent of complex events (chromothripsis and chromoanasynthesis)… A protein–protein network enrichment highlighted biological pathways involved in immunity and bone development.” DOI: 10.3390/ijms241310463. https://doi.org/10.3390/ijms241310463 (pires2023analysisofthe pages 2-5). - Liu 2023 (Bone Research; Jan 2023): “mregDCs promote tumor immune tolerance through recruitment of Tregs… CNV-high cells exhibited reduced interferon‑gamma pathway activity and lower MHC‑I (HLA‑A, HLA‑B, HLA‑E) and B2M expression… CD24 was identified as a novel ‘don’t eat me’ signal that contributed to the immune evasion of OS cells.” DOI: 10.1038/s41413-022-00237-6. https://doi.org/10.1038/s41413-022-00237-6 (liu2023characterizingthetumor pages 2-3). - Zheng 2024 (J Cancer Res Clin Oncol; Jul 2024): “Chemotherapy caused the remaining OS cells to express higher levels of genes associated with stemness… enhances the presence of cancer-associated fibroblasts, increasing their ability to modify the extracellular matrix… reduced the immune cell population, including myeloid and T/NK cells, particularly subpopulations with tumor-fighting capabilities.” DOI: 10.1007/s00432-024-05787-2. https://doi.org/10.1007/s00432-024-05787-2 (zheng2024singlecelltranscriptomicinsights pages 1-2). - Al‑Ansari 2024 (Biomolecules; Jan 2024): summarizes ranges for chromothripsis (~20–89%) and kataegis (~50–85%) and high frequencies of TP53 (75–90%) and RB1 (50–78%) defects pooled from literature (context for variability across cohorts). DOI: 10.3390/biom14020145. https://doi.org/10.3390/biom14020145 (alansari2024unveilingtheprotective pages 6-8).

Disease progression (sequence of events) 1) Initiation: developmental osteoblast/MSC lineage acquires catastrophic structural lesions (chromothripsis/kataegis), with early loss of TP53/RB1/ATRX and focal oncogene gains (MYC/MDM2) (nirala2023decipheringthesignaling pages 1-2, pires2023analysisofthe pages 2-5). 2) Clonal selection: dysregulated PI3K/AKT/mTOR, Wnt/β‑catenin, TGF‑β, NOTCH, Hedgehog, JAK/STAT and NF‑κB drive proliferation, survival, osteoid production, invasion (nirala2023decipheringthesignaling pages 2-4). 3) Microenvironmental conditioning: RANK/RANKL promotes osteoclastogenesis; TAMs (SPP1+) and mregDCs accumulate; cancer cells reduce MHC‑I/B2M and elevate PD‑L1/CD24 to evade immunity (liu2023characterizingthetumor pages 2-3). 4) Metastatic dissemination: EMT-like programs, ECM remodeling, and chemotactic axes enable intravasation and lung colonization; AKT1/FGFR signaling contribute to invasive/metastatic phenotypes (nirala2023decipheringthesignaling pages 2-4, chen2025harnessingmultiomicsto pages 4-5). 5) Treatment remodeling: chemotherapy enriches stem-like tumor cells and CAF-driven ECM programs while depleting effectors, fostering resistance and recurrence (zheng2024singlecelltranscriptomicinsights pages 1-2).

Phenotypic manifestations (link to mechanisms) - Clinical: destructive metaphyseal bone lesions with periosteal reaction; osteoid production by malignant cells; high propensity for lung metastases. Mechanistic correlates: osteoblast-lineage origin with RANKL–osteoclast crosstalk; ECM remodeling and immune evasion supporting dissemination (nirala2023decipheringthesignaling pages 2-4, liu2023characterizingthetumor pages 2-3).

Citations and metadata (URLs and dates) - Nirala BK et al., Int J Mol Sci, Jul 2023, https://doi.org/10.3390/ijms241411367 (nirala2023decipheringthesignaling pages 2-4, nirala2023decipheringthesignaling pages 1-2). - Pires SF et al., Int J Mol Sci, Jun 2023, https://doi.org/10.3390/ijms241310463 (pires2023analysisofthe pages 2-5). - Liu W et al., Bone Research, Jan 2023, https://doi.org/10.1038/s41413-022-00237-6 (liu2023characterizingthetumor pages 2-3). - Zheng X et al., J Cancer Res Clin Oncol, Jul 2024, https://doi.org/10.1007/s00432-024-05787-2 (zheng2024singlecelltranscriptomicinsights pages 1-2). - Al‑Ansari N et al., Biomolecules, Jan 2024, https://doi.org/10.3390/biom14020145 (alansari2024unveilingtheprotective pages 6-8). - Chen X et al., Int J Mol Med, Apr 2025, https://doi.org/10.3892/ijmm.2025.5533 (chen2025harnessingmultiomicsto pages 4-5).

Notes on evidence scope - Where possible, we prioritized 2023–2024 primary and integrative studies; one 2025 precision‑medicine review is included to connect AKT/FGFR signaling to metastasis and resistance. Future updates should incorporate emerging 2024–2026 genomics (e.g., chromothripsis dynamics) as they are peer‑reviewed.

References

1. (nirala2023decipheringthesignaling pages 2-4): Bikesh K. Nirala, Taku Yamamichi, and Jason T. Yustein. Deciphering the signaling mechanisms of osteosarcoma tumorigenesis. International Journal of Molecular Sciences, 24:11367, Jul 2023. URL: https://doi.org/10.3390/ijms241411367, doi:10.3390/ijms241411367. This article has 41 citations and is from a poor quality or predatory journal.

2. (pires2023analysisofthe pages 2-5): Sara Ferreira Pires, Juliana Sobral de Barros, Silvia Souza da Costa, Gabriel Bandeira do Carmo, Marília de Oliveira Scliar, André van Helvoort Lengert, Érica Boldrini, Sandra Regini Morini da Silva, Daniel Onofre Vidal, Mariana Maschietto, and Ana Cristina Victorino Krepischi. Analysis of the mutational landscape of osteosarcomas identifies genes related to metastasis and prognosis and disrupted biological pathways of immune response and bone development. International Journal of Molecular Sciences, 24:10463, Jun 2023. URL: https://doi.org/10.3390/ijms241310463, doi:10.3390/ijms241310463. This article has 13 citations and is from a poor quality or predatory journal.

3. (alansari2024unveilingtheprotective pages 6-8): Nojoud Al-Ansari, Samson Mathews Samuel, and Dietrich Büsselberg. Unveiling the protective role of melatonin in osteosarcoma: current knowledge and limitations. Biomolecules, 14:145, Jan 2024. URL: https://doi.org/10.3390/biom14020145, doi:10.3390/biom14020145. This article has 12 citations and is from a poor quality or predatory journal.

4. (chen2025harnessingmultiomicsto pages 4-5): Xuesong Chen, Bin Tian, Yiqun Wang, Jiang Zheng, and Xin Kang. Harnessing multi-omics to revolutionize understanding and management of osteosarcoma: a pathway to precision medicine (review). International Journal of Molecular Medicine, 55:1-20, Apr 2025. URL: https://doi.org/10.3892/ijmm.2025.5533, doi:10.3892/ijmm.2025.5533. This article has 2 citations and is from a peer-reviewed journal.

5. (liu2023characterizingthetumor pages 2-3): Weijian Liu, Hongzhi Hu, Zengwu Shao, Xiao Lv, Zhicai Zhang, Xiangtian Deng, Qingcheng Song, Yong Han, Tao Guo, Liming Xiong, Baichuan Wang, and Yingze Zhang. Characterizing the tumor microenvironment at the single-cell level reveals a novel immune evasion mechanism in osteosarcoma. Bone Research, Jan 2023. URL: https://doi.org/10.1038/s41413-022-00237-6, doi:10.1038/s41413-022-00237-6. This article has 78 citations and is from a domain leading peer-reviewed journal.

6. (zheng2024singlecelltranscriptomicinsights pages 1-2): Xuejing zheng, Wence Wu, Zhen-guo Zhao, Xin-xin Zhang, and Shengji Yu. Single-cell transcriptomic insights into chemotherapy-induced remodeling of the osteosarcoma tumor microenvironment. Journal of Cancer Research and Clinical Oncology, Jul 2024. URL: https://doi.org/10.1007/s00432-024-05787-2, doi:10.1007/s00432-024-05787-2. This article has 5 citations and is from a peer-reviewed journal.

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Comprehensive Pathophysiology of Osteosarcoma: Molecular Mechanisms, Cellular Dysfunction, and Disease Progression

Osteosarcoma (OS) represents the most common primary malignant bone tumor affecting adolescents and young adults, characterized by rapid, aggressive growth and a high propensity for early metastatic dissemination[36]. Despite significant advances in multimodal treatment approaches combining neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy, the five-year survival rate for patients with localized disease remains approximately 65 percent, dropping dramatically to approximately 25 percent for those presenting with metastatic disease[47]. This comprehensive analysis elucidates the complex, multifactorial pathophysiology underlying osteosarcoma development, with particular emphasis on the molecular mechanisms driving tumorigenesis, disease progression, and therapeutic resistance. The disease arises from dysregulation of fundamental cellular processes including genome integrity maintenance, proliferative control, differentiation programming, metabolic adaptation, immune surveillance, and cell-cell communication within the tumor microenvironment. Understanding these interconnected mechanisms provides critical insights into potential therapeutic interventions and prognostic biomarkers.

Genetic and Epigenetic Alterations Driving Osteosarcoma Development

Tumor Suppressor Gene Inactivation: The Role of TP53 and RB1

The molecular foundation of osteosarcoma development centers on the inactivation of two critical tumor suppressor genes, TP53 and RB1, which regulate fundamental cellular processes including DNA damage response, cell cycle progression, and apoptosis[2][4][5]. Remarkably, whole-genome sequencing studies have demonstrated that approximately 95 percent of osteosarcomas exhibit disruption of the p53 pathway, despite the relatively low prevalence of simple point mutations in sporadic tumors[4]. This paradox has been resolved through identification of complex structural variations and chromosomal translocations that effectively inactivate TP53 function without producing detectable point mutations through conventional analysis methods. Inactivation of the tumor suppressor p53 from translocation into the first intron of the TP53 gene has been detected in 9 out of 19 patient osteosarcoma tumors examined[4]. The most frequent TP53 rearrangements identified include TP53-VAV1, TP53-EMR1, TP53-PPRAD, and TP53-KPNA3, with these fusion products resulting in functional inactivation of p53[4]. Notably, TP53-KPNA3 translocations have been specifically associated with chemotherapy resistance and metastasis[4].

The retinoblastoma pathway similarly exhibits profound dysregulation in the vast majority of osteosarcomas. RB1 mutations are detected in approximately 70 percent of all adolescent osteosarcomas[2], and patients carrying germline mutations in RB1 demonstrate approximately a 500-fold higher incidence of osteosarcoma compared to the general population[2]. At the molecular level, RB1 loss leads to aberrant spliceosome function through upregulation of E2F3a, a mediator of spliceosome gene expression[1]. Critically, while RB1 loss alone proves insufficient to establish osteosarcoma in animal models, robust synergy between TP53 and RB1 inactivation has been demonstrated in osteosarcoma development, with compound mutant mice developing osteosarcoma in 75 percent of animals and exhibiting substantially shortened lifespans compared to single mutant animals[2].

The MDM2 oncogene, which encodes a critical negative regulator of p53, exhibits amplification and overexpression in approximately 17 percent of osteosarcomas[5]. Amplification and overexpression of MDM2 can lead to increased MDM2-p53 binding, resulting in inactivation of p53 function[5]. Remarkably, MDM2 amplification occurs independently of TP53 mutations, suggesting complementary mechanisms of p53 pathway inactivation[5]. Collectively, alterations of the TP53, RB1, and MDM2 genes account for abnormalities in 62 percent of osteosarcomas examined in earlier studies[5].

Structural Variants and Chromosomal Complexity

Recent comprehensive genomic studies have fundamentally shifted understanding of osteosarcoma genetics by revealing that structural variations (SVs) and copy number alterations (CNAs), rather than single nucleotide variations (SNVs), represent the primary mechanism of recurrent mutations in osteosarcoma[4]. Whole genome sequencing from the St. Jude Children's Research Hospital – Washington University Pediatric Cancer Genome Project identified high rates of structural variations and copy number alterations but notably low rates of single nucleotide variations in osteosarcoma tumors[4]. This unique mutational landscape fundamentally distinguishes osteosarcoma from many other malignancies and poses significant challenges for implementing traditional targeted mutation-based therapies.

Clonal evolution analysis of osteosarcoma patients reveals that 62 percent of patient tumors exhibit a simple linear evolutionary pattern, whereas 38 percent display branching evolutionary patterns or contain only single clone clusters[20]. Notably, linear evolutionary patterns predominate in nonmetastatic tumors, whereas metastatic tumors display no clear evolutionary trend, suggesting distinct mechanisms of progression. Among identified mutations, ATRX mutations frequently occur as early events in metastatic tumors and confer strong clonal selectivity advantages[20]. The ATRX gene encodes a chromatin remodeling protein closely related to chromatin remodeling and telomere maintenance[20]. ATRX mutations may lead to genomic instability and increased tumor cell survival, thereby strongly influencing clonal expansion associated with metastasis[20]. Furthermore, analysis of high-frequency gene mutations revealed that CNV in TP53 and ATRX were more prevalent in the metastatic group compared to nonmetastatic tumors, with patients harboring metastases at diagnosis demonstrating generally poorer prognosis[20].

Chromoanagenesis and Catastrophic Chromosomal Rearrangements

A particularly striking feature of osteosarcoma genomics involves chromoanagenesis, encompassing chromothripsis and chromoanasynthesis, representing catastrophic chromosomal rearrangement events[38]. Chromothripsis, characterized by massive chromosomal shattering followed by random reassembly of fragmented DNA, results in complex segmental copy number alterations and is among the most striking examples of chromothripsis-driven malignancy[38]. Osteosarcoma represents one of the malignancies most profoundly driven by chromothripsis, which contributes significantly to profound genome complexity[38]. This mechanism intersperses chromothripsis patterns with segmental amplifications across multiple chromosomes, achieving biallelic TP53 inactivation and enabling tolerance to whole-genome duplication in approximately half of high-grade osteosarcomas while simultaneously amplifying multiple oncogenes through multi-generational breakage-fusion-bridge cycles[38].

The breakage-fusion-bridge cycle mechanism results from dicentric chromosomes via telomere fusions, which frequently rupture during mitosis, causing catastrophic fragmentation and chromothripsis-like rearrangements often accompanied by kataegis[38]. These mechanisms precipitate chromothriptic fragmentation of missegregated DNA within micronuclei, followed by clonal selection of survival-advantageous rearrangements, thereby underpinning the pervasive copy number alterations observed in 78 percent of certain osteosarcoma models and the oscillating genomic patterns characteristic of chromothripsis[38]. The five most frequently affected chromosomes in osteosarcoma cases with chromoanagenesis are chromosomes 12, 1, 8, 6, and 2[38].

MYC Amplification and Cell Cycle Dysregulation

Multi-region whole-genome sequencing of pediatric osteosarcoma has revealed that amplification of the MYC oncogene represents a major driver of childhood osteosarcoma[45]. Reanalysis of copy number readouts from 258 cases of high-grade osteosarcoma across three different cohorts identified significant enrichment of focal MYC amplifications in children[45]. Furthermore, four additional cases of MYC and CCNE1 coamplification have been identified, representing a rare driver event warranting further investigation[45]. MYC amplification demonstrates association with inferior outcomes in survival analysis conducted on integrated datasets[45]. Although CCNE1 amplification did not correlate with adverse survival in all datasets examined, CCNE1 remains a recognized driver in multiple malignancies including osteosarcoma, having been proven to serve as an independent prognostic factor in triple-negative breast cancer and ovarian cancer[45].

MYC has been demonstrated to directly regulate CCNE1 gene expression as well as CCNE1-CDK2 complex activity[45]. Mouse models have demonstrated the cooperative action of MYC and CCNE1 in contributing to tumor formation in hepatocellular cancer and other malignancies[45]. The cyclin-dependent kinase complexes, particularly cyclin D-CDK4/6 and cyclin E-CDK2 complexes, sequentially phosphorylate retinoblastoma proteins to release restriction of the G1/S checkpoint, thereby allowing cells to enter S phase[29]. Dysregulation of these cell cycle regulatory complexes through MYC and CCNE1 amplification promotes uncontrolled cell cycle progression characteristic of osteosarcoma.

Dysregulation of Major Signaling Pathways

PI3K/AKT/mTOR Pathway Hyperactivation

The PI3K/AKT/mTOR signaling pathway represents one of the most important oncogenic pathways frequently hyperactivated in osteosarcoma[10][7]. This pathway plays a crucial role in promoting tumor cell proliferation, migration, epithelial-mesenchymal transition, inhibition of apoptosis, and increasing sensitivity to chemotherapy drugs[7]. The pathway becomes dysregulated through multiple mechanisms, with loss of the PTEN gene being a particularly common mechanism leading to overactivation of the PI3K pathway in osteosarcoma patients[7]. During activation, p-Akt promotes activation of mTORC1, which then influences cellular activities directly through its own catalytic actions[7]. Overactivation of this pathway in tumor patients occurs primarily due to dysregulation in the expression of PIK3CA and phosphatase and tensin homolog (PTEN)[7].

The PI3K/AKT/mTOR pathway has been identified as an osteosarcoma driver through sleeping beauty transposon-based forward genetic screening approaches which introduce mutations into the genome[4]. Upstream regulation of this pathway involves increased uptake of leucine and glutamine in osteosarcoma cells through upregulation of LAT2, which activates mTORC1 and subsequent c-Myc-mediated transcription of CD47, enabling evasion of innate immune mechanisms and thereby promoting metastasis[1]. Targeting this pathway through small molecule compounds represents an attractive potential therapeutic approach for osteosarcoma[10].

The interaction between the PI3K/AKT/mTOR pathway and non-coding RNAs has emerged as a critical regulatory mechanism. The long non-coding RNA DANCR binds to miR-33a-5p in a competitive manner, thereby increasing the expression of RTK AXL, which influences expression of downstream proteins in the PI3K/Akt pathway and affects various aspects of tumor cells, such as the self-renewal of cancer stem cells and EMT[7]. Similarly, the lncRNA ANRIL performs an essential function in prognostic prediction of osteosarcoma patients, with ANRIL expression in osteosarcoma tissues notably higher than in adjoining non-cancerous tissues[7]. ANRIL enhances the proliferation and invasion of osteosarcoma cells, and its knockdown appreciably induces mobile apoptosis and confirms association with negative prognosis, specifically through decreased phosphorylation levels of PI3K and Akt[7].

Multiple microRNAs regulate components of the PI3K/AKT/mTOR pathway in osteosarcoma. Downregulation of miR-384 promotes tumor growth by upregulating SLBP and activating the PI3K/Akt pathway[7]. MiR-1224-5p, which is downregulated in osteosarcoma tissues, negatively regulates the PI3K/Akt/mTOR pathway and inhibits tumor growth and EMT[7]. MiR-564, downregulated in osteosarcoma patients, directly targets Akt, inhibits its transcription and translation, and suppresses tumor cell glycolysis, thereby inhibiting cell proliferation[7]. CircRNA-NIRP1, upregulated in osteosarcoma, competitively binds to miR-532-3p to upregulate Akt3, thereby enhancing the activity of the PI3K/Akt pathway and strengthening malignancy[7].

Wnt/β-Catenin Signaling and RUNX2 Regulation

WNT/β-catenin signaling is over-activated in osteosarcoma and promotes tumor progression[8][11]. Importantly, the WNT/β-catenin pathway normally activates RUNX2 gene expression during osteogenic lineage commitment, and this pathway has been demonstrated to control the tumor-related elevation of RUNX2 expression in osteosarcoma[8][11]. Analysis of protein levels and nuclear localization of β-catenin and RUNX2 in human osteosarcoma cell lines reveals that in all six examined cell lines (SAOS, MG63, U2OS, HOS, G292, and 143B), β-catenin and RUNX2 are expressed to different degrees and localized in both the nucleus and cytoplasm[8][11]. Notably, SAOS cells demonstrate the highest levels of RUNX2 protein localized in the nucleus, while MG63 cells exhibit the lowest RUNX2 levels predominantly localized in the cytoplasm[8][11].

Treatment with the GSK3β inhibitor SB216763 enhances levels of both β-catenin and RUNX2 protein in HOS, G292, and 143B cells[8][11]. Small interfering RNA-mediated depletion of β-catenin inhibits RUNX2 expression in G292 cells, demonstrating that WNT/β-catenin activation is required for RUNX2 expression in at least some osteosarcoma cell types, where RUNX2 is known to promote expression of metastasis-related genes[8][11]. This pathway dysregulation represents a critical mechanism by which normal developmental signals become hijacked to promote malignant progression.

JAK-STAT Pathway and Immune Modulation

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway comprises seven STAT members involved in the regulation of cell proliferation, differentiation, and survival[1]. Activation of STAT1 in osteosarcoma cells suppresses epithelial-mesenchymal transition, resulting in increased apoptosis and cell cycle arrest, and decreased colony formation, cell migration, and invasion[1]. Conversely, increased expression of COL6A1 promotes STAT1 degradation, which subsequently facilitates osteosarcoma metastasis[1]. This pathway thus represents a potential therapeutic target, as enhancement of STAT1 activity could theoretically restore anti-tumor differentiation programs.

NRF2 and Oxidative Stress Management

NRF2 regulates intracellular reactive oxygen species balance, the AMPK/mTOR autophagy signaling pathway, and the Warburg effect[1]. TRIM22 inhibits osteosarcoma progression by binding to and destabilizing NRF2 in a KEAP1-independent manner[1]. This mechanism highlights how dysregulation of oxidative stress response pathways contributes to osteosarcoma pathogenesis by allowing cells to survive under conditions that would normally trigger apoptosis.

Molecular Pathways Driving Metastatic Progression

Epithelial-Mesenchymal Transition and Migration

The epithelial-mesenchymal transition (EMT) represents a vital step in osteosarcoma progression toward metastasis[13]. This process is associated with a reduction in epithelial-like features of cancer cells and acquisition of mesenchymal-like features necessary to mediate effective invasion and migration[13]. The EMT is a common event observed in a wide range of cancer types undergoing metastasis, and several transcription factors including Twist1, Snail, and ZEB1 cooperate to control this complex process[13].

Although osteosarcoma cells arise from cells that descend from the mesenchyme, they maintain partial epithelial characteristics, including some epithelial markers necessary to mediate cohesiveness during migration and to allow resistance to mechanical stress experienced during migration[13]. Downregulation of miR-22 contributes to epithelial-mesenchymal transition in osteosarcoma, with miR-22 being downregulated in human osteosarcoma in a manner correlating with enhanced tumor progression and metastasis[13]. Overexpression of miR-22 significantly reduces cell proliferation and substantially suppresses epithelial-mesenchymal transition in osteosarcoma cells[13]. Specifically, miR-22 directly targets Twist1 to mediate repression of EMT, with miR-22 expression being negatively correlated with Twist1 expression in patient samples[13].

At the molecular level, cells overexpressing miR-22 demonstrate reduced Vimentin expression and increased E-cadherin expression, directly corresponding to significant reduction in osteosarcoma cell EMT capacity[13]. These findings highlight that miR-22/Twist1 signaling axis represents a clinically relevant regulatory node for EMT control in osteosarcoma, suggesting potential utility as either a prognostic biomarker or therapeutic target[13].

HIF-1α and Hypoxic Adaptation

Hypoxia-inducible factor-1α (HIF-1α) plays an essential role in the mechanisms of osteosarcoma metastasis and has been demonstrated to facilitate rapid tumor cell adaptation to hypoxic environments, thereby contributing to metastatic processes[30]. During hypoxia, HIF-1α expression levels and stability increase, with increased HIF-1α promoting tumor vascular remodeling, epithelial-mesenchymal transformation, and osteosarcoma cell invasiveness, ultimately leading to distant metastasis[30]. Meta-analysis of nine published studies comprising 486 osteosarcoma cases demonstrated that overexpression of HIF-1α correlates with lower survival rate, higher microvessel density, metastasis, higher pathologic grade, tumor stage, and poor chemotherapy response in osteosarcoma[27].

After translocation into the nucleus, HIF-1α binds to HIF-1β, forming a transcriptional complex that binds to hypoxia response elements in the promoter regions of target genes, thereby initiating transcriptional expression of many downstream genes participating in various physiological and pathological processes[30]. HIF-1α is subject to regulation by various factors including the antisense transcription factor aHIF-1α, which exerts negative regulatory effects on transcription of the HIF-1α gene[30]. The regulation of osteosarcoma cell metastasis by HIF-1α involves multiple mechanisms including modulation of invasive and metastatic potential, promotion of EMT processes, enhancement of cellular adhesion, increase in anti-apoptotic properties, induction of immune evasion, facilitation of tumor angiogenesis, and fostering of microenvironmental remodeling[30].

Hypoxia-induced upregulation of miR-18b-5p through HIF-1α transcriptional control inhibits expression of tumor suppressor gene PHD finger protein 2 at the post-transcriptional level, with the miR-18b-5p-PHF2 signal axis involved in HIF-1α-mediated metastasis of osteosarcoma[30]. Under hypoxic conditions, expression of E-cadherin becomes upregulated, while expression of Vimentin, N-cadherin, and snail protein becomes downregulated; all these proteins serve as markers for EMT[30]. With upregulation of HIF-1α and TWIST family bHLH transcription factor 1 expression, E-cadherin expression becomes downregulated, leading to altered EMT processes in osteosarcoma cells[30].

Vascular Endothelial Growth Factor and Angiogenesis

VEGF expression and high vascularity within osteosarcoma correlate with poor prognosis[9]. Studies examining the correlation between VEGF expression with tumor stage and metastasis revealed significantly positive correlation between VEGF expression and tumor stages[9]. Data further suggest higher cancer recurrence and more frequent cases of remote metastasis in high-VEGF groups compared to low-VEGF groups[9]. VEGF expression positively associates with c-fos and c-myc expressions in primary tumor sections[9]. Prior data suggested probability of lung metastasis in VEGF-negative osteosarcoma was 0.15, whereas the incidence ratio of lung metastasis in VEGF-positive osteosarcoma was 0.82[9].

Pro-angiogenic factors become up-regulated in tumors, with such up-regulation linked to poor prognosis[9]. Pro-angiogenic factors within solid tumors stimulate host vascular endothelial cell mitogenesis and possibly chemotaxis. Multiple pro-angiogenic factors have been identified including basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor beta-1, transforming growth factor alpha, and epidermal growth factor[9]. VEGF represents the best characterized pro-angiogenic factor, being relatively unique among growth factors in its specificity for the vascular endothelium[9]. Not only does VEGF function as a diffusible endothelium-specific mitogen and angiogenic factor, it also increases vascular permeability and stimulates maintenance of neovascularization in various tumor types[9].

Metabolic Reprogramming in Osteosarcoma

Aerobic Glycolysis and the Warburg Effect

Tumor cells undergo profound metabolic reprogramming to meet their energy and anabolic demands necessary for maintaining their malignant phenotype. Aerobic glycolysis, also known as the Warburg effect, supports biosynthesis and metabolic processes necessary for osteosarcoma growth and metastasis[1]. Key enzymes involved in this process, such as PGC1α, PKM2, ALDOA, and LDHA, can directly influence tumor progression and metastasis[1]. For instance, miR-23b-3p downregulates PGC1α and promotes a metabolic shift from oxidative phosphorylation to glycolysis, supporting osteosarcoma progression[1]. This metabolic reprogramming enables rapid ATP generation necessary to support the elevated biosynthetic and proliferative demands of malignant cells.

Metabolic reprogramming in tumor cells mainly involves the glycolytic pathway, pentose phosphate pathway, serine synthesis pathway, enhanced glutamine metabolism or fatty acid anabolism, and abnormal mitochondrial oxidative phosphorylation[31][34]. The tricarboxylic acid cycle represents the central pathway of mitochondrial oxidative phosphorylation, with glucose, amino acid, and fatty acid metabolism all associated with the TCA cycle[31][34]. Genetic alterations in tumor cells, including those involving p53 and other oncogenic and tumor suppressive pathways, promote metabolic reprogramming directly or indirectly by regulating enzymatic activities associated with metabolic pathways[31][34].

Glutamine Metabolism and GLS-1 Inhibition

Highly metastatic osteosarcoma cell lines require glutamine for proliferation, and conversely, glutaminase-1 (GLS-1) inhibition limits metastatic progression in osteosarcoma[1]. This finding identifies glutamine metabolism as a critical dependency of metastatic osteosarcoma cells. Glutamine serves as both an energy source through the TCA cycle and a biosynthetic precursor for nucleotide and amino acid synthesis, making it particularly critical for rapidly proliferating cancer cells. The dependence on glutamine metabolism in metastatic osteosarcoma versus primary tumors suggests that the metastatic phenotype becomes increasingly dependent on specific metabolic pathways that might represent therapeutic vulnerabilities.

RNA Modifications and Gene Expression Control

RNA modifications, particularly m6A methylation, play critical roles in osteosarcoma metastasis through regulation of mRNA stability and protein expression. The m6A demethylase FTO mediates mRNA demethylation, promoting decay of KLF3 mRNA and decreasing its expression, consequently facilitating osteosarcoma proliferation and metastasis[1]. Additionally, the destabilizing effects of FTO on DACT1 mRNA promote Wnt signaling and consequently osteosarcoma metastasis[1]. ALKBH5-mediated m6A methylation upregulates expression of USP22 and RNF40, subsequently inhibiting ubiquitination of histone H2A and promoting osteosarcoma growth and metastasis[1]. Upregulation of TRIM7 due to loss of m6A RNA modifications has been reported to promote osteosarcoma metastasis and chemoresistance by inducing ubiquitination of BRMS1[1].

Cellular Origins and Cancer Stem Cell Biology

Mesenchymal Stem Cell Versus Osteoblast Origin Hypotheses

There exist two primary competing hypotheses regarding the cellular origin of osteosarcoma, the mesenchymal stem cell (MSC) origin hypothesis and the osteoblast origin hypothesis[3][4]. The MSC hypothesis proposes that a mutation-carrying MSC will give rise to osteosarcoma[4]. A high frequency of pathogenic variants in the TP53 and RB1 tumor suppressor genes and the c-MYC and RAS oncogenes is found in genomic studies of human osteosarcoma[4]. However, mounting evidence increasingly places cells that undergo osteoblast commitment rather than immature MSCs as the most likely cell-of-origin for osteosarcoma[6].

During osteogenic differentiation, depletion of Trp53 or both Trp53 and Rb1 in murine bone marrow-derived MSCs, but notably not in adipose-derived MSCs, induces formation of osteosarcoma-like tumors[4]. This observation suggests that osteoblasts rather than MSCs represent the cells of origin of osteosarcoma. Supporting this notion, RUNX2 and WNT signaling pathways, essential for osteogenic differentiation, have been found disrupted in human osteosarcoma samples, demonstrating loss of RUNX2 transcriptional activity and nuclear accumulation of β-Catenin, thus indicating that osteosarcoma development might entail differentiation defects[4].

When comparing cells-of-origin directly, P53/RB-disrupted immature MSC and osteoblast committed cells all proved capable of initiating OS formation, though at varying incidence levels[6]. This finding demonstrates that all types of cells along the osteogenic lineage possessed capacity to initiate osteosarcoma formation, with findings influenced by certain microenvironment signals[6]. Importantly, the level of osteoblastic differentiation of tumors did not correlate with the degree of differentiation of the cell-of-origin, suggesting that epigenetic dedifferentiation mechanisms could be active in mature osteoblasts during osteosarcomagenesis[6].

Evidence of undifferentiated MSC as cell-of-origin for osteosarcoma derives from introduction of other oncogenic events into undifferentiated bone marrow MSCs, such as expression of C-MYC in a P16INK4A−/− P19ARF−/− genetic background or aneuploidization accompanied by loss of the INKA locus, resulting in osteosarcoma development[6]. Nevertheless, accumulated evidence most strongly supports concepts that osteosarcoma development is initiated by different cell types along the mesenchymal-osteogenic lineage targeted with relevant oncogenic lesions, like inactivation of tumor suppressor genes P53 and RB, and becomes highly influenced by bone microenvironment signals[6].

Cancer Stem Cell Characteristics and Maintenance

Experimental evidence supports the notion that sarcomas are hierarchically organized and sustained by a subpopulation of self-renewing cells that can generate the full repertoire of tumor cells and display tumor reinitiating properties[6]. CSC subpopulations emerge after accumulation of further epigenetic and genetic alterations in a cell within the aberrant population initially generated by the cell-of-origin[6]. Hypothesis to explain resistance of osteosarcoma to chemotherapy involves existence of drug-resistant cancer stem cells with progenitor properties responsible for tumor relapses and metastasis[6]. These subpopulations of CSCs commonly emerge during tumor evolution from the cell-of-origin, which represents the normal cells acquiring the first cancer-promoting mutations to initiate tumor formation[6].

CD133 and C-X-C chemokine receptor type 4 (CXCR4) represent frequently applied markers for cancer stem cells in osteosarcoma patients[14]. mRNA of stemness genes such as octamer-binding transcription factor 4 (Oct-4) and NANOG, as well as the metastasis-related receptor CXCR4, are highly expressed in CD133+ osteosarcoma cells[14]. CD133 expression serves as an independent prognostic factor associated with lung metastasis and poor prognosis of osteosarcoma patients[14]. Concomitant expression of CSC markers CD133/CXCR4 might represent a novel marker for predicting poor prognosis in osteosarcoma patients, with CD133 and CXCR4 potentially serving as therapeutic targets[14].

Tumor Microenvironment and Immune Evasion

Tumor-Associated Macrophages and Immune Suppression

Tumor-associated macrophages (TAMs) represent the most prevalent immune cells in the tumor microenvironment[15][18]. In osteosarcoma, TAMs may constitute over 50 percent of immune cells, significantly influencing tumor initiation, progression, metastasis, immunosuppression, and drug resistance[18]. Both circulating monocytes and tissue-resident macrophages contribute to accumulation of TAMs, with secreted chemokines from tumor cells and stromal cells, such as macrophage colony-stimulating factor (M-CSF) and C-C motif ligand 2 (CCL-2), inducing and recruiting monocytes to the tumor microenvironment[15]. Notably, TAMs were recruited by interleukin-34 (IL-34) released from osteosarcoma cells, with IL-34 released by osteosarcoma cells promoting recruitment of M2-TAMs into tumor tissue to promote tumor growth and metastasis[15][18].

The osteosarcoma tumor microenvironment exhibits extensive macrophage infiltration, predominantly myeloid CD163+ cells, potentially facilitating tumor immune evasion[18]. M2-related cytokines, chemokines, and cell markers are overexpressed in pulmonary osteosarcoma metastasis[18]. M2 macrophages become enriched in primary osteosarcoma tissue, activating tumor stem cells and inducing drug resistance[18]. TAMs modulate local immunity, angiogenesis, and malignant cell migration, primarily promoting tumor growth by facilitating macrophage polarization toward anti-inflammatory phenotype and enhancing immune infiltration[18].

Metastatic osteosarcoma cells display a more malignant phenotype via exosomal communication with macrophages, with these exosomes significantly increasing M2 macrophage-related cytokines such as IL10 and transforming growth factor-beta 2, thereby modulating macrophages toward tumor-promoting M2 phenotype[15]. This conversion contributes to inhibition of macrophage-mediated tumor surveillance and promotion of immunosuppression within the microenvironment[15]. Infiltrating CD68+ cells were elevated in tumor tissues of osteosarcoma patients poorly reactive to neoadjuvant chemotherapy, with macrophages secreting IL-1β after chemotherapy treatment, activating downstream cancer signaling pathways and reducing sensitivity of osteosarcoma to chemotherapeutic drugs[15].

T Cell Dysfunction and Checkpoint Exhaustion

The osteosarcoma tumor microenvironment features an inhibitory immune microenvironment with higher numbers of TIM-3+ PD-1+ T cells compared to peripheral blood[18]. This specific immune suppression of TIM-3+ PD-1+ T cells becomes amplified by M2 TAMs[18]. T cell activation plays pivotal roles in tumor immune response through two pathways: interaction between T cell receptor and major histocompatibility complex presenting antigens, and binding of co-stimulatory transmembrane receptor CD28 on T cells to its ligands CD80/86[39]. Tumor-infiltrating lymphocytes predominantly localize in areas expressing human leukocyte antigen class I, whereas CD4+ and CD8+ T cells concentrate at the interface of lung metastases[39].

Natural Killer Cell Suppression

In the osteosarcoma microenvironment, NK cells become suppressed, with TGF-β expression elevated[39]. TGF-β plays pivotal role in diminishing natural killer cell-mediated killing, with tumor-derived TGF-β downregulating activation receptor expression such as NKG2D on NK cells, impairing their ability to recognize and kill osteosarcoma cells[42]. Furthermore, osteosarcoma cells frequently shed soluble ligands for NKG2D, further inhibiting NK cell-mediated cytotoxicity[42]. Infiltration of NK cells in osteosarcoma demonstrates association with gender, with male patients possessing 71 percent more NK cells compared to female patients[18]. The underlying mechanism involves TGF-β promoting angiogenesis, bone remodeling, and cell migration by suppressing expression of activated receptor NKG2D and decreasing release of NK cell-killing perforin[18].

Regulatory T Cells and Myeloid-Derived Suppressor Cells

Regulatory T cells (Tregs) play dual-edged role in osteosarcoma pathogenesis, not only assisting tumor cells in evading immune surveillance but also playing key role in promoting tumor angiogenesis[18][39]. Within the osteosarcoma microenvironment, Tregs operate through various mechanisms, secreting immunosuppressive cytokines including IL-10, IL-35, and TGF-β to hinder activity of effector T cells and suppress osteoclast formation via direct cell contact-dependent means[18][39]. Myeloid-derived suppressor cells (MDSCs) inhibit T cell proliferation, diminish T cell-mediated immune responses, and promote T cell apoptosis by depleting L-arginine and generating reactive oxygen species within the microenvironment[18]. Additionally, MDSCs suppress functionality of NK cells and dendritic cells[18]. Furthermore, under hypoxic microenvironment stimuli, MDSCs facilitate angiogenesis and establishment of pre-metastatic niches, closely linked to osteosarcoma metastasis[18].

Osteoclasts and Bone Remodeling

Loss of osteoclasts contributes to development of osteosarcoma metastasis, with ablation of osteoclasts with zoledronic acid increasing number of metastatic lung lesions in orthotopic osteosarcoma models, whereas fulvestrant treatment increases osteoclast numbers and reduces metastatic lesions[40]. Tartrate-resistant acid phosphatase (ACP5/TRAP) is significantly downregulated in osteosarcoma compared with nonmalignant bone, with lesions from osteosarcoma patients with pulmonary metastases demonstrating 2-fold less ACP5/TRAP expression than lesions from patients without metastases[40]. Mature bone-resorbing osteoclasts secrete several enzymes including tartrate-resistant acid phosphatase 5, considered the classic marker for bone resorption and osteoclast differentiation[40]. Metastatic osteosarcoma cells prove significantly more migratory in presence of bone marrow factors than nonmetastatic cells, with osteoclasts secreting factors that significantly reduce migration of metastatic osteosarcoma cells[40].

Disease Progression, Metastasis, and Clinical Manifestations

Staging and Prognostic Factors

Osteosarcoma tumors are classified based on whether they are localized in one place or metastatic, meaning they have spread to other parts of the body[33]. Low-grade, localized tumors represent stage I osteosarcoma; high-grade, localized tumors represent stage II; and metastatic tumors (regardless of grade) represent stage III[33]. The Musculoskeletal Tumor Society (MSTS) staging system, also known as the Enneking system, bases staging on three key pieces of information: tumor grade (G), extent of primary tumor (T) classified as either intracompartmental or extracompartmental, and presence of metastasis (M)[33].

Site of main tumor influences prognosis significantly, with tumors arising from bones of arms or legs often demonstrating better outlook than those in pelvis or spine[33]. Size of main tumor affects prognosis as well, with smaller tumors proving easier to surgically remove than larger tumors[33]. Histological characteristics significantly influence outcome, with high-grade tumors demonstrating high cell-to-matrix ratio, poor differentiation, and malignant cytologic characteristics including degree of pleomorphism, mitotic index, lymphovascular invasion, amount of necrosis, and invasiveness[56]. Grade I and grade II osteosarcomas demonstrate significantly better prognosis than grade III osteosarcomas[56].

Clinical Presentation and Diagnostic Approaches

Most common presenting symptom of osteosarcoma represents bone pain, initially with activity then at rest[54]. Pain and swelling at local site, usually at growing ends of an extremity or long bones, constitute most common presenting symptoms[51]. Around 10 percent of patients present with pathological fractures due to primary tumors or bony metastases[51]. Systemic symptoms seen in other malignancies remain rare[51]. Respiratory symptoms indicating extensive lung involvement remain uncommon[51]. Physical examination findings typically focus on primary tumor location, including palpable tender mass, decreased range of motion of adjacent joint with possible effusion, pain on weight-bearing or inability to bear weight, and local or regional lymphadenopathy[51].

Diagnosis of osteosarcoma requires multidisciplinary approach integrating clinical evaluation, imaging, and laboratory testing[36]. Radiographs of conventional osteosarcoma usually demonstrate medullary and cortical bone destruction with mixed lytic and blastic appearance, with high-grade osteosarcoma often described as demonstrating permeative or "moth-eaten" appearance with "sunburst" configuration due to aggressive periostitis or "Codman triangle" configuration due to elevation of periosteum away from bone[51]. MRI is utilized to assess local invasion, while CT and bone scans help evaluate metastatic spread[36]. Elevated alkaline phosphatase levels support diagnosis by indicating increased bone turnover[36]. Definitive diagnosis requires biopsy and histopathological analysis, with staging subsequently determined based on tumor size, metastatic involvement, and histological grade to guide treatment planning[36].

Metastatic Disease and Lymph Node Involvement

Approximately 10 to 20 percent of osteosarcoma patients present with metastases, primarily to the lungs[51]. The lung metastases, representing the primary target of metastasis in osteosarcoma, demonstrate five-year survival rates of approximately 30 percent[57]. In extrapulmonary metastatic osteosarcoma, patients with lymph node metastases demonstrate worse clinical outcomes, with five-year survival rates of only 10 percent[57]. However, only 3 percent of osteosarcoma patients are diagnosed with lymph node metastasis, leading to lack of adequate clinical data for exploring lymph node involvement in osteosarcoma[57].

Osteosarcoma lymphatic metastasis demonstrates significant association with distant metastasis, with osteosarcoma lymphatic metastasis being significantly associated with poor prognosis[57]. Osteosarcoma metastases, typically secondary to hematogenous dissemination, represent secondary events of profound prognostic significance[57]. Due to lack of lymphatic drainage in normal cortical and spongy bone, lymph node metastasis remains rare in bone sarcomas[57]. Regional lymph node involvement in osteosarcoma may result from infiltration of enlarged tumor parenchyma into periphery, such as joint capsule or synovium, leading to dissemination into lymphatic system[57].

Therapeutic Resistance and Chemotherapy Escape

Mechanisms of Drug Resistance

Osteosarcoma remains difficult to treat, with standard chemotherapy regimen having not improved survival for past three decades, with resistance to chemotherapy remaining major clinical challenge[44]. Multiple molecular mechanisms contribute to chemoresistance in osteosarcoma, including decreased intracellular accumulation of drugs, inactivation of drugs, improved DNA repair, modulations of signaling pathways, resistance linked to autophagy, disruption in genes expression linked to cell cycle, and implications of microenvironment[22].

Impaired drug transport represents one described resistance mechanism to chemotherapy in osteosarcoma, particularly due to decreased transporters on tumor cell surfaces[22]. Increased drug efflux has been reported as partly responsible for osteosarcoma resistance, with cancer cells exposed to one chemotherapy agent developing resistance to many other anticancer drugs, called multidrug resistance[22]. This acquired resistance results mainly from overexpression of members of ATP-binding cassette family of efflux transporters[22]. P-glycoprotein associates with cytoskeleton linker named ezrin, with complex located in plasma membrane lipid rafts, and multidrug resistance in osteosarcoma cell lines could result from this cytoskeleton linker, with ezrin inhibition increasing drug sensitivity and ezrin expression associating with poor outcomes[22].

Alterations in structure or expression of target enzyme can explain resistance of some chemotherapeutic agents through increased levels of target enzymes or decreased drug affinity due to mutations[22]. MTX-resistant osteosarcoma cell lines exhibit high expression of DHFR, with relationship demonstrated between high DHFR expression in xenografts and emergence of resistance[22]. Osteosarcoma cells treated with DOX or CDP exhibit upregulation of GSTP1 expression, with GSTP1 expression inducible by chemotherapeutic agents leading to resistance of tumor cells[22]. GSTP1 overexpression was associated with failure of preoperative chemotherapy, suggesting that overexpression associates with chemotherapy failure[22].

Autophagy-Mediated Survival and Drug Resistance

Autophagy demonstrates dual role in osteosarcoma, potentially promoting cell survival by protecting malignant cells from unfavorable conditions while also serving as tumor suppressor by impairing malignant transformation and promoting malignant cell death[44]. Activation of PI3K/AKT/mTOR signaling pathway inhibits autophagy in osteosarcoma, with use of rapamycin, an mTOR inhibitor, inducing autophagy and increasing cell death in osteosarcoma cells[44]. HMGB1-mediated autophagy induction leads to chemotherapy resistance, with inhibition of both HMGB1 and autophagy leading to increased drug sensitivity[44].

The dual role of autophagy proves context-dependent, with different osteosarcoma cell lines and treatments demonstrating distinct autophagy-outcome relationships[44]. Treatment of murine osteosarcoma cell lines with camptothecin induced autophagy, but autophagy inhibition decreased CPT-induced cell death in one line while increasing it in another[44]. Similarly, treatment of human osteosarcoma cell lines with gemcitabine induced autophagy, with autophagy inhibition increasing cell death in certain lines while increasing survival in others[44]. This duality proves not species-specific, with effects observed in mouse and human cells alike[44].

miRNA-Mediated Chemoresistance Regulation

MiR-26a expression declines in chemoresistant osteosarcoma after neoadjuvant chemotherapy, with expression correlating with clinical outcome[19]. Compared with sensitive parental cells, miR-26a expression also declines in osteosarcoma multidrug-resistant cells[19]. Enforced expression of miR-26a reverses multidrug resistance in osteosarcoma cells, while miR-26a knockdown confers multidrug resistance in chemosensitive osteosarcoma cells treated with doxorubicin, methotrexate, or cisplatin[19]. MiR-26a reverses resistance to doxorubicin in osteosarcoma multidrug-resistant cells xenografted in nude mice[19]. The critical mechanism by which miR-26a negatively regulates multidrug resistance in osteosarcoma involves targeting and suppressing MCL1 expression, with restored MCL1 expression substantially recovering chemoresistance caused by miR-26a enforcement[19].

Conclusion: Integrating Pathophysiology into Therapeutic Development

Osteosarcoma represents a complex, heterogeneous malignancy driven by multifactorial dysregulation of fundamental cellular processes encompassing genome integrity, proliferative control, differentiation programming, metabolic adaptation, immune surveillance, and microenvironmental interactions. The disease arises from inactivation of critical tumor suppressors TP53 and RB1, often accompanied by structural chromosomal variations, copy number alterations, and catastrophic rearrangement events including chromothripsis. These genetic alterations initiate transformation in cells along the osteogenic lineage under influence of specific microenvironmental signals, generating cancer stem cell populations responsible for metastatic dissemination and therapeutic resistance. Dysregulation of major signaling pathways including PI3K/AKT/mTOR, Wnt/β-catenin, and HIF-1α drive proliferation, migration, and angiogenesis. Metabolic reprogramming enables aggressive tumor growth through Warburg effect activation and glutamine dependency. The tumor microenvironment becomes extensively infiltrated with immunosuppressive cell populations including macrophages, regulatory T cells, and myeloid-derived suppressor cells, facilitating immune evasion. Multiple mechanisms of chemotherapy resistance emerge through drug transport alterations, enhanced DNA repair, autophagy-mediated survival, and microRNA-regulated pathway dysregulation.

Future therapeutic strategies must address this complex pathophysiology through multiple complementary approaches. Direct targeting of dysregulated signaling pathways through small molecule inhibitors and biologics shows promise, particularly approaches targeting PI3K/AKT/mTOR and immune checkpoints. Restoration of p53 function through MDM2 inhibitors or synthetic lethality approaches exploiting DNA repair deficiencies represents another avenue. Metabolic therapy targeting glutamine metabolism and glycolysis offers additional possibilities. Immunotherapeutic approaches using checkpoint blockade combined with strategies to convert immunosuppressive macrophages toward anti-tumor phenotypes show emerging potential. Patient-derived preclinical models integrating comprehensive genomic profiling and functional testing will increasingly enable discovery of tumor-specific vulnerabilities. Continued investigation of the interactions between genetic alterations, signaling dysregulation, metabolic transformation, and microenvironmental influence will ultimately drive development of personalized, multimodal therapeutic strategies improving outcomes for this aggressive malignancy affecting adolescents and young adults.