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 ARv567es are 2 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 ARv567es to delineate similarities and differences in transcriptomics, metabolomics, and lipidomics resulting from the activation of AR, ARv7, or ARv567es. While the majority of target genes were similarly regulated by the action of all 3 isoforms, we found a clear difference in transcriptomic activities of AR versus the variants, and a few differences between ARv7 and ARv567es. 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.