The histone lysine demethylase, GASC1 (Gene Amplified in Squamous Cell Carcinoma 1) is an epigenetic regulatory protein both highly expressed during mammalian embryogenesis and overexpressed in several types of cancer, including aggressive Castration Resistant Prostate Cancer (CRPC). GASC1 mainly catalyzes demethylation of tri- and di-methylated forms of histone H3 lysine 9 (H3K9me3/me2) epigenetic repressive marks, regulating gene expression and chromatin architecture. This research aims to elucidate the fundamental mechanism by which GASC1 dysregulation contributes to CRPC progression, as well as to evaluate its potential as a therapeutic target against aggressive prostate cancer. Previously, our lab and others have shown that GASC1 interacts with the androgen receptor (AR) and functions as a co-activator of AR-induced transcription in prostate cancer. We have used an shRNA approach to determine whether GASC1 knockdown affects the proliferation and transformation of CRPC cells. We found that knocking down GASC1 inhibits the growth and colony formation of C4-2B and CWR22Rv1 cells in vitro. Knockdown also reduced transcript levels of classical and CRPC-specific AR target genes in either the presence or absence of the AR ligand. As a result, we are evaluating the therapeutic potential of novel and highly specific lysine demethylase inhibitors towards abating GASC1 function in prostate cancer cells in vitro. We have recently determined that one of these novel inhibitors is highly effective in modulating the survival and proliferation of several prostate cancer cell lines including CRPC lines with IC50 values, all well under 1 uM. Together, our data demonstrates that GASC1 is a therapeutically relevant target in controlling and preventing the emergence of prostate cancers, with particular application against aggressive CRPC subtypes.

Citation Format: Roselyne M. Labbe, Qin Ye, Andreana Holowatyj, Lihong Zhang, Zeng Quan Yang. Mechanism and therapeutic potential of the histone demethylase GASC1 in castration-resistant prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5152. doi:10.1158/1538-7445.AM2014-5152