mTOR Adaptive Resistance to Androgen Deprivation Module

Pharmacology Oncology Module mtor_androgen_deprivation_resistance 1 disorder Pathograph 6

A conserved resistance-mechanism module capturing PI3K/AKT/mTOR-driven adaptive resistance to androgen-receptor (AR) pathway blockade in prostate cancer. Androgen deprivation therapy (ADT) and AR-signaling inhibitors (ARPIs) impose a selective pressure on AR-dependent tumor cells; because the AR and PI3K/AKT/mTOR pathways are reciprocally cross-regulated, suppression of AR relieves feedback inhibition of the PI3K/AKT axis (classically potentiated by PTEN loss), driving compensatory mTORC1 hyperactivation. The hyperactive mTORC1 node sustains pro-survival translational and metabolic programs that keep tumor cells alive under androgen blockade, producing adaptive (castration) resistance and treatment failure. Because the reciprocal wiring means inhibiting one pathway activates the other, the therapeutic rationale of the module is co-targeting: pharmacologic mTOR inhibition combined with AR-pathway inhibition, which can be captured with target_mechanisms on conforming treatments (e.g., everolimus plus abiraterone acetate). Individual disorder entries declare conformance via conforms_to, substituting the tumor-context-specific lesion (PTEN loss, PIK3CA/AKT1 activation) and the specific ARPI/mTOR-inhibitor pair.

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Pathophysiology Nodes

5 shared nodes are defined in this module.

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Cell Types

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Biological Processes

Androgen Receptor Signaling Pathway GO:0030521 DECREASED PI3K/AKT Signal Transduction GO:0043491 INCREASED TORC1 Signaling GO:0038202 INCREASED TOR Signaling GO:0031929 INCREASED Positive Regulation of Translation GO:0045727 INCREASED Androgen-Independent Tumor Cell Proliferation GO:0008283 INCREASED

Notes

This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "mtor_androgen_deprivation_resistance#mTORC1 Hyperactivation"). The module defines the expected pathophysiology structure; conforming nodes in disorder files should include the corresponding biological processes and causal edges, specialized to their tumor context. Key tumor-context substitutions: PTEN deletion (the most common route, ~40% of primary and ~70% of metastatic disease) relieving PI3K feedback; PIK3CA or AKT1 activating alterations; the specific ARPI used (abiraterone, enzalutamide) and mTOR inhibitor (everolimus, temsirolimus, rapamycin). Key conformance / treatment target: "mtor_androgen_deprivation_resistance#mTORC1 Hyperactivation". This module is the mechanistic complement to AI-derived morphometric predictors of ADT response: the INR-like ("incomplete/non-responder") tumor state defined by such predictors converges on this mTOR-hyperactive resistance axis, providing the biological explanation for why co-targeting mTOR re-sensitizes resistant tumors to AR blockade.

Mechanistic Hypotheses

mTOR inhibition re-sensitizes ADT-resistant tumors to AR blockade

mtor_resensitization EMERGING

The hypothesis that pharmacologic mTOR inhibition, added to AR-pathway blockade, overcomes adaptive resistance in the PI3K/AKT/mTOR-hyperactive (castration-resistant / INR-like) subset. Preclinical co-inhibition data are strong (near-complete regressions with combined PI3K and AR blockade in murine and xenograft models); prospective clinical confirmation of the specific mTOR-inhibitor-plus-ARPI combination in a morphometrically or molecularly defined resistant subgroup is still emerging.

Discussions and Knowledge Gaps

Can pharmacologic inhibition of mTORC1 actually break the reciprocal PI3K/AKT-AR feedback loop this module is built around, given that rapalogs only partially inhibit mTORC2 and therefore themselves elicit the same PI3K/AKT-induced feedback, and that everolimus monotherapy produced no PSA responses in metastatic castration-resistant prostate cancer?

KNOWLEDGE GAP OPEN gap_mtor_adt_rapalog_feedback_and_monotherapy_failure

Attached to: mTORC1 Hyperactivation

The module's therapeutic arm asserts that inhibiting mTORC1 relieves the resistant phenotype, but the cited review documents the reverse running through the same loop the module models: "the rapalog family only has a partial inhibition of mTORC2. As a result, the associated inhibition of mTORC1 can elicit PI3K/AKT-induced positive feedback mechanisms that constrain the durable effectiveness of the therapeutic responses" (PMID:41525007). The clinical record is correspondingly negative — in NCT00976755 everolimus monotherapy in 37 post-docetaxel mCRPC patients showed "minimal clinical effectiveness, and no patient displayed a PSA response, with a median PFS of only 3 months". Combination evidence for the strategy remains preclinical (PMID:21575859, Pten-deficient murine and xenograft models); the one combination trial named in the review (NCT00814788, everolimus plus bicalutamide) is cited without an outcome. Until a combination trial reports, whether the mTORC1 node is a tractable drug target in this disease or only a mechanistic waypoint is genuinely open, and conforming disorder entries must not curate rapalog therapy as an effective intervention on the strength of this module.

Proposed experiments: Rapalog versus dual mTORC1/mTORC2 inhibitor, each combined with an AR-pathway inhibitor

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Used By Disorder Entries

Prostate Adenocarcinoma via Signaling Bypass and Castration Resistance → mTORC1 Hyperactivation

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Pathograph

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Pathophysiology

Androgen Receptor Pathway Blockade

trigger

Androgen deprivation therapy or an AR-signaling inhibitor (ARPI) suppresses androgen-receptor transcriptional output, the therapeutic starting point that imposes selective pressure on AR-dependent prostate cancer cells. AR cross-talk with oncogenic survival pathways is the substrate on which resistance is built; conforming disorder nodes substitute the specific agent (ADT, abiraterone, enzalutamide).

Androgen Receptor Signaling Pathway GO:0030521 DECREASED

Downstream

Reciprocal PI3K/AKT Feedback Activation

Reciprocal PI3K/AKT Feedback Activation

amplifier

Because the AR and PI3K/AKT pathways cross-regulate each other by reciprocal feedback, suppression of AR signaling relieves feedback inhibition of the PI3K/AKT axis (for example, by reducing the AKT phosphatase PHLPP), so AR blockade paradoxically activates AKT signaling. PTEN loss, the most common PI3K-pathway lesion in prostate cancer, sensitizes the tumor to this compensatory activation. Conforming disorder nodes substitute the specific PI3K-pathway lesion (PTEN deletion, PIK3CA/AKT1 activation).

PI3K/AKT Signal Transduction GO:0043491 INCREASED

Downstream

mTORC1 Hyperactivation

mTORC1 Hyperactivation

central effector

Compensatory PI3K/AKT activation converges on constitutive mTOR complex 1 (mTORC1) signaling, the rate-limiting, disorder-agnostic central node of the module and the pharmacologic target of rapalogs. Hyperactive mTORC1 is the conserved point through which every conforming tumor funnels its ADT-resistant survival signaling, and its activity distinguishes resistant (incomplete/non-responder) from sensitive tumors.

Prostate luminal tumor cell CL:0002340

TORC1 Signaling GO:0038202 INCREASED TOR Signaling GO:0031929 INCREASED

Used by disorders

Prostate Adenocarcinoma as Signaling Bypass and Castration Resistance

Downstream

Pro-Survival Translational and Metabolic Reprogramming

Pro-Survival Translational and Metabolic Reprogramming

effector

Hyperactive mTORC1 drives cap-dependent protein translation and anabolic metabolism (via effectors such as S6K1/p70S6K and 4E-BP1), sustaining biosynthesis, growth, and survival programs that compensate for the loss of AR-driven survival signals under androgen blockade. p70S6K, a direct mTORC1 effector, is a robust functional readout of this node.

Positive Regulation of Translation GO:0045727 INCREASED

Downstream

Adaptive Resistance to Androgen-Deprivation Therapy

Adaptive Resistance to Androgen-Deprivation Therapy

consequence

The net consequence: mTOR-sustained survival signaling renders tumor cells able to grow independently of androgen, producing adaptive (castration-resistant) growth and clinical failure of ADT/ARPI monotherapy. This is the resistant/incomplete-responder phenotype that co-targeting the mTOR node aims to reverse.

Androgen-Independent Tumor Cell Proliferation GO:0008283 INCREASED