Isoform specific activities of androgen receptor and its splice variants in prostate cancer cells

Androgen receptor (AR) signaling continues to drive castration resistant prostate cancer (CRPC) in spite of androgen deprivation therapy (ADT). Constitutively active shorter variants of AR, lacking the ligand binding domain, are frequently expressed in CRPC and have emerged as a potential mechanism for prostate cancer to escape ADT. ARv7 and AR v567es are two of the most commonly detected variants of AR in clinical samples of advanced, metastatic prostate cancer. It is not clear if variants of AR merely act as weaker substitutes for AR or can mediate unique isoform specific activities different from AR. In this study, we employed LNCaP prostate cancer cell lines with inducible expression of ARv7 or AR v567es to delineate similarities and differences in transcriptomics, metabolomics and lipidomics resulting from the activation of AR, ARv7 or AR v567es. While the majority of target genes were similarly regulated by the action of all three isoforms, we found a clear difference in transcriptomic activities of AR versus the variants, and a few differences between ARv7 and AR v567es. Some of the target gene regulation by AR isoforms was similar in the VCaP background as well. Differences in downstream activities of AR isoforms were also evident from comparison of the metabolome and lipidome in an LNCaP model. Overall our study implies that shorter variants of AR are capable of mediating unique downstream activities different from AR and some of these are isoform specific.

23-O-Substituted-2,3-Dehydrosilybins Selectively Suppress Androgen Receptor-Positive LNCaP Prostate Cancer Cell Proliferation

As part of our ongoing project to search for natural product-based antiandrogens, nine derivatives of 2,3-dehydrosilybin have been synthesized for the evaluation of its antiproliferative activity in an androgen receptor-positive prostate cancer cell model. Specifically, 3,5,7,20- O-tetramethyl-2,3-dehydrosilybin was synthesized through two approaches, and eight 23- O-substituted-3,5,7,20- O-tetramethyl-2,3-dehydrosilybins were achieved from 3,5,7,20- O-tetramethyl-2,3-dehydrosilybin. The antiproliferative potency of 3,5,7,20- O-tetramethyl-2,3-dehydrosilybin and its eight derivatives were assessed in an androgen receptor (AR)-positive LNCaP prostate cancer cell line, as well as in two AR-negative (PC-3 and DU145) prostate cancer cell models as a comparison. Our WST cell proliferation assay data indicate 3,5,7,20- O-tetramethyl-2,3-dehydrosilybin and most of its 23- O-substituents can selectively inhibit AR-positive LNCaP prostate cancer cell proliferation. Our data suggest that 3,5,7,20- O-tetramethyl-2,3-dehydrosilibins could serve as a natural product-based scaffold for new antiandrogens for lethal castration-resistant prostate cancer.