GSE132062
Alternative splicing of LSD1+8a is mediated by SRRM4 in Neuroendocrine Prostate Cancer
Neuroendocrine prostate cancer (NEPC) is the most virulent subtype. Currently, there is an urgent need to identify new biomarkers and therapeutic targets in NEPC. The splicing factor SRRM4 was previously demonstrated to be highly expressed in NEPC, to promote expression of genes linked to neuroendocrine differentiation and cancer progression, and to promote alternate splicing of genes, including REST. One of REST's binding protein is lysine specific demethylase 1 (LSD1). Importantly,  a transcript variant of LSD1 called LSD1+8a is expressed in neuronal tissues and promotes neuronal gene expression.  However, there was no information about LSD1+8a's importance in prostate cancer. Using adenocarcinoma and NEPC patient-derived xenografts and clinical specimens, we determined that LSD1+8a was expressed exclusively in NEPC. Furthermore, LSD1+8a  expression was significantly correlated with elevated mRNA expression of SRRM4.  Using SRRM4-overexpressing prostate cancer cell lines, we determined that alternative splicing of LSD1+8a is directly mediated by SRRM4 and that LSD1+8a and SRRM4 co-regulate a unique program of cancer-promoting genes that is not regulated by canonical LSD1. Our findings demonstrate that measurement of LSD1+8a expression is a promising NEPC biomarker and suggest that targeting LSD1+8a in NEPC may be a useful strategy to block expression of genes linked to cancer progression. Overall design: We analyzed differential gene expression in LNCaP (clone FGC) cells transiently transfected with LSD1, LSD1+8a, SRRM4, and empty vector