Abstract A043: Functional PTEN loss rewires AR-AKT crosstalk and alters therapeutic response in a novel AR-positive prostate cancer model

Abstract Functional loss of the tumor suppressor phosphatase and tensin homolog (PTEN) is detected in ∼40–60% of advanced prostate cancers and is linked to hyperactivation of the PI3K/AKT pathway, therapeutic resistance, and disease progression. However, most existing PTEN-deficient models lack androgen receptor (AR) expression, limiting investigation of the AR-AKT signaling interplay. We generated and characterized a novel CRISPR/Cas9-mediated PTEN knockout (KO) CWR-R1 model that retains functional AR signaling in both enzalutamide-sensitive (Parental/Par) and enzalutamide-resistant (EnzR) contexts. WGS, RNA-seq and Western blot validation confirmed complete PTEN loss and enrichment of PI3K/AKT signatures. PTEN deficiency increased phosphorylation of AKT (Ser473), S6 kinase and GSK-3β, consistent with constitutive pathway activation. Drug sensitivity profiling using the AKT inhibitor AZD5363 (Capivasertib) demonstrated a dose-dependent reduction in cell viability across all PTEN KO clones, with IC50 values markedly lower than WT controls (Par WT: 0.66 μM vs. KO clones: 0.18–0.50 μM; EnzR WT: >10 μM vs. KO clones: 0.11–0.53 μM), indicating enhanced pathway dependence. In contrast, PTEN loss modulated AR-targeted therapy response in a context-dependent manner: while Par KO clones displayed stable or reduced response to AR antagonists, EnzR KO clones exhibited partial re-sensitization, suggesting adaptive AR-AKT feedback regulation under PTEN-deficient conditions. Collectively, these findings establish the first AR-expressing CWR-R1 PTEN-KO system to dissect AR–AKT crosstalk under clinically relevant resistance settings. These findings reveal that PTEN loss enhances AKT pathway dependence and alters AR inhibitor responsiveness, supporting rational dual-pathway therapeutic strategies in PTEN-deficient prostate cancer. Citation Format: Shauna McClelland, Cristina Branco, Simon T. Barry, Cath Eberlein, Melissa J. LaBonte-Wilson. Functional PTEN loss rewires AR-AKT crosstalk and alters therapeutic response in a novel AR-positive prostate cancer model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Innovations in Prostate Cancer Research and Treatment; 2026 Jan 20-22; Philadelphia PA. Philadelphia (PA): AACR; Cancer Res 2026;86(2_Suppl):Abstract nr A043.