Endocrine Abstracts

Neuroendocrine castrate resistant prostate cancer (NE-CRPC) is a lethal CRPC subtype that arises as prostate cancer cells transdifferentiate to neuroendocrine cells, evading the potent selective pressure of androgen deprivation therapies (ADT). Currently, clinicians lack biomarkers to detect NE-CRPC evolution and specific therapies to target it. With ~50% of prostate cancer (PC) patients receiving ADT and NE-CRPC accounting for ~25% of CRPC deaths, CRPC and NE-CRPC are a significant clinical challenge. Whilst neuroendocrine transdifferentiation (NEtD) of PC is not fully understood, there are several parallels between NE-CRPC and small cell lung cancer (SCLC); an aggressive neuroendocrine lung tumour. Driver of neurogenesis, ASCL1, is essential for SCLC survival and SCLC switching to a neuroendocrine-like lineage to escape chemotherapy. We have shown ASCL1 induction accompanies NEtD of PCa. Whether ASCL1 actively initiates NEtD of CRPC and/or maintains the NE-CRPC phenotype is unknown. We investigated ASCL1’s role in driving NEtD by culturing androgen-sensitive LNCaP cells in androgen-deprived conditions with the potent anti-androgen, Enzalutamide, to model NEtD. ASCL1 target genes (DLL1, DLL3, HES6), cell fate (NOTCH1-3), androgen signalling (AR, KLK3) and neuroendocrine (ENO2, TUBB3) gene expression was analysed by qRT-PCR. Morphological and molecular changes associated with NEtD of LNCaP cells (loss KLK3, induction of ASCL1, ENO2 & TUBB3) were accompanied by marked induction of DLL1 and NOTCH3. Temporal analysis showed initial induction of ASCL1 that was sustained and accompanied by an initial increase, and subsequent decrease in DLL1 expression, suggesting these may be involved in driving NEtD. CRISPR knockout will ascertain if ASCL1 is essential to initiate and maintain NEtD of LNCaP cells. This data indicates ASCL1 is active during early NEtD of CRPC by inducing direct and indirect target genes that may initiate NE-CRPC formation, akin to SCLC evolution. In future, this knowledge may facilitate development of precision therapies to target lethal NE-CRPC.