Regulation of Apoptosis by a Prostate-Specific and Prostate Cancer-Associated Noncoding Gene, PCGEM1

Abstract

PCGEM1 is a prostate tissue-specific, and prostate cancer-associated noncoding RNA (ncRNA) gene. Previous results revealed a significant association of elevated PCGEM1 expression levels in prostate cancer cells of African-American patients, whose mortality rate is the highest among prostate cancer patients. Functional study of PCGEM1 demonstrated a marked increase in colony formation in LNCaP prostate cancer cells and NIH3T3 mouse fibroblast cells. This study demonstrates that PCGEM1 overexpression in LNCaP cell culture model results in the inhibition of apoptosis induced by doxorubicin (DOX). Induction of p53 and p21(Waf1/Cip1) by DOX were delayed in LNCaP cells stably overexpressing PCGEM1 (LNCaP-PCGEM1 cells) compared to control LNCaP cells. The protein levels of cleaved caspase 7, and cleaved PARP were attenuated in DOXtreated LNCaP-PCGEM1 cells compared to control LNCaP cells. Similar results were observed in LNCaP cells transiently overexpressing PCGEM1. The inhibition of PARP cleavage by PCGEM1 overexpression was also observed in LNCaP-PCGEM1 cells incubated with etoposide and sodium selenite. Fluorescence-Activated Cell Sorter Annexin-V analysis revealed significantly lower percentage of apoptotic cells in DOX-treated LNCaP-PCGEM1 cells compared to control LNCaP cells. The attenuation of apoptic response appears to be androgen dependent in this experimental model, as androgen-independent variants of LNCaP cells did not exhibit this response. In summary, this study provides new insights into cell biologic functions and novel features of an ncRNA. Further, these data unravel biological mechanisms of cell growth/cell survival-associated functions of this ncRNA in a widely used prostate cancer cell culture model.