Androgen receptor as therapeutic indicator for LAR-positive triple-negative breast cancer: Preclinical and clinical assessment.

Triple-negative breast cancer (TNBC) is an aggressive disease with limited treatment options, where the luminal androgen receptor (LAR+) subtype presents a promising target for AR-directed therapy. However, the impact of AR splice-variants on responses to bicalutamide (Bica) and enzalutamide (Enza) is not well understood across various breast cancer forms. This study investigated Bica and Enza in the LAR + TNBC (MDA-MB-453), the AR-low TNBC (MDA-MB-231), and the ER + luminal (MCF-7) cells, using both 2D monolayer and 3D spheroid cultures. It examined AR splice-variant expression, cell-cycle progression, viability, and nuclear AR immunohistochemistry in TNBC patient samples from India. In 2D cultures, these drugs showed subtype-specific effects: in MDA-MB-453, both reduced AR-V7 and caused G1 arrest, with Bica exerting a stronger effect; in MDA-MB-231, Bica and Enza differentially regulated AR-V1, AR-V4, AR-V5, and AR-V6 without significant cell-cycle alterations. In MCF-7, Enza induced G1 arrest alongside changes in AR variants. In 3D spheroids, drug responses differed markedly from 2D conditions, and co-treatment with dihydrotestosterone (DHT) emphasized context-dependent AR signaling. Nuclear AR was detected in 30% of Indian TNBC samples. Overall, the findings reveal that AR splice variants vary in expression and regulation across breast cancer subtypes, and that treatment effectiveness is influenced by the splice-variant profile, ER-AR interactions, and the tumor environment. Total AR protein alone is insufficient for patient stratification. These insights support the inclusion of AR splice-variant analysis in biomarker-based strategies to enable precise AR-targeted therapies in breast cancer.