Understanding the contribution of the AR to the emergence of highly lethal, drug-resistant NEPC is critical for better implementation of current standard-of-care therapies and novel drug design. Our first-in-field data underscore the consequences of potent AR inhibition in prostate tumors, revealing a novel mechanism of AR-dependent control of neuroendocrine differentiation, and uncover BRN2 as a potential therapeutic target to prevent emergence of NEPC. Cancer Discov; 7(1); 54-71. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 1.

Resistance to antiandrogen drugs, like MDV3100, occurs in patients with castration-resistant prostate cancer (CRPC). Thus, preventing or treating antiandrogen resistance is a major clinical challenge. We identified a novel antiandrogen, Compound 30, and compared its efficacy with MDV3100. We found that Compound 30 inhibits androgen receptor (AR) activity in LNCaP cells, C4-2 cells, as well as MDV3100-resistant cell lines. Compared with MDV3100, Compound 30 treatment induces greater reduction in AR, prostate-specific antigen (PSA), and AR transcriptional activity, and prevents AR nuclear translocation in AR-sensitive LNCaP cells. Compound 30 has antiproliferative effects in LNCaP cells, in castrate-resistant C4-2 cells, and those resistant to MDV3100. Compound 30 was equally as effective as MDV3100 in reducing tumor volume and PSA in vivo. More importantly, Compound 30 is effective at inhibiting AR activity in MDV3100-resistant cell lines and significantly prevented tumor growth and PSA increases in mice bearing MDV3100-resistant xenografts. Together, our data show that Compound 30 strongly inhibited AR activity and suppressed castration-resistant LNCaP growth as well as MDV3100-resistant cell growth in vitro and in vivo. These data provide a preclinical proof-of-principle that Compound 30 could be a promising next generation anti-AR agent, especially in the context of antiandrogen-resistant tumors. Mol Cancer Ther; 12(5); 567–76. ©2013 AACR.

Growth factor receptor tyrosine kinase (RTK) pathway activation is a key mechanism for mediating cancer growth, survival, and treatment resistance. Cognate ligands play crucial roles in autocrine or paracrine stimulation of these RTK pathways. Here, we show SEMA3C drives activation of multiple RTKs including EGFR, ErbB2, and MET in a cognate ligand‐independent manner via Plexin B1. SEMA3C expression levels increase in castration‐resistant prostate cancer (CRPC), where it functions to promote cancer cell growth and resistance to androgen receptor pathway inhibition. SEMA3C inhibition delays CRPC and enzalutamide‐resistant progression. Plexin B1 sema domain‐containing:Fc fusion proteins suppress RTK signaling and cell growth and inhibit CRPC progression of LNCaP xenografts post‐castration in vivo. SEMA3C inhibition represents a novel therapeutic strategy for treatment of advanced prostate cancer.

YB-1 appears to be a promising target to inhibit the development of castration resistance, even at the AR variant-expressing stage. Polymorphism in the YB-1 gene may be a promising predictive biomarker in hormonal therapy.