Abstract 957: Regulation of PCGEM1 in castration resistant prostate cancer

PCGEM1 has been shown to be prostate cancer specific long non-coding RNA (lncRNA). Our previous study indicates that PCGEM1 plays a role in castration resistance through regulation of androgen receptor (AR) splice variants. Although it is known that PCGEM1 is often upregulated in prostate cancer, little is known how PCGEM1 is regulated. In the present study, we show that p54/nrb is a positive regulator for PCGEM1. PCGEM1 is higher in castration resistant CWR22Rv1 than in androgen sensitive LNCaP cells. Moreover, androgen deprivation induces PCGEM1 in LNCaP cells. Histone ChIP assays suggest that the active binding site is within 500 bp upstream of putative transcriptional start site. By using biotin-labelled PCR product and pulldown assays combined with mass spectrometry analysis, we show that p54/nrb interacts with the promoter of PCGEM1. While ectopic expression increases, suppression of p54/nrb by RNAi or knockout (KO) suppresses PCGEM1, supporting a role for p54/nrb in PCGEM1 regulation. Moreover, rescue experiments indicate that re-expression of p54/nrb in KO cells restores the ability to induce PCGEM1. Finally, 3, 3’-Diindolylmethane (DIM), a known chemoprevention agent derived from plants such as broccoli, is capable of suppressing PCGEM1 expression by preventing the interaction of p54/nrb with the PCGEM1 promoter. In particular, DIM reduces tumor growth by suppression of PCGEM1 and promoting apoptosis in the castrated xenograft mouse model. Together, these results demonstrate a novel mechanism of how PCGEM1 and AR splicing are regulated. As a result, PCGEM1 may ultimately contribute to castration resistance. Citation Format: Tsui-Ting Ho, Yin-Yuan Mo. Regulation of PCGEM1 in castration resistant prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 957.