Sigma1 Targeting to Suppress Aberrant Androgen Receptor Signaling in Prostate Cancer

We reported previously that some Sigma1-selective small molecules can be used to pharmacologically modulate protein homeostasis pathways. We hypothesized that these Sigma1-mediated responses could be exploited to suppress AR protein levels and activity. Here we demonstrate that treatment with a small-molecule Sigma1 inhibitor prevented 5α- dihydrotestosterone-mediated nuclear translocation of AR and induced proteasomal degradation of AR and ARV, suppressing the transcriptional activity and protein levels of both full-length and splice-variant AR. Consistent with these data, RNAi knockdown of Sigma1 resulted in decreased AR levels and transcriptional activity. Furthermore, Sigma1 physically associated with ARV7 and ARv567es as well as full-length AR. Treatment of mice xenografted with ARV-driven CRPC tumors with a drug-like small-molecule Sigma1 inhibitor significantly inhibited tumor growth associated with elimination of AR and ARV7 in responsive tumors. Together, our data show that Sigma1 modulators can be used to suppress AR/ARV–driven prostate cancer cells via regulation of pharmacologically responsive Sigma1-AR/ARV interactions, both in vitro and in vivo. Cancer Res; 77(9); 2439–52. ©2017 AACR.

Source: Cancer Research - April 30, 2017 Category: Cancer & Oncology Authors: Jeffrey D. Thomas, Charles G. Longen, Halley M. Oyer, Nan Chen, Christina M. Maher, Joseph M. Salvino, Blase Kania, Kelsey N. Anderson, William F. Ostrander, Karen E. Knudsen, Felix J. Kim Tags: Therapeutics, Targets, and Chemical Biology Source Type: research