PAX6 promotes neuroendocrine phenotypes of prostate cancer via enhancing MET/STAT5A-mediated chromatin accessibility
Neuroendocrine prostate cancer (NEPC) is a highly aggressive form of prostate cancer characterized by the loss of androgen receptor (AR) signaling and the acquisition of neuroendocrine (NE) characteristics. However, the underlying molecular mechanism, especially related to the drivers or the determinants responsible for NE transdifferentiation, remains unclear. In this study, we compared gene expression profiling of NEPC and non-NEPC specimens and paid a particular attention to those transcriptional factors affecting neural differentiation during development. We identified that Paired box 6 (Pax6) expression was significantly elevated in NEPC and negatively regulated by AR signaling. While knock-down of Pax6 in NEPC cells inhibited NEPC phenotypes, over-expression of Pax6 in non-NEPC cells led to development of NEPC. Mechanistically, loss of AR resulted in an enhanced expression of Pax6, which reprogramed the lineage plasticity of prostate cancer cells to develop NE phenotypes through the c-Met/Stat5a signaling. By performing ATAC-seq, we found that high expression level of Pax6 elicited enhanced chromatin accessibility mainly through attenuation of H4K20me3 that usually causes chromatin silence in cancer cells. Taken together, these findings highlight PAX6 as a novel molecule to drive NEPC progression and suggest that it might serve as a potential target for the management of NEPC. Overall design: To investigate the role of PAX6 in the differentiation of LNCaP cell line from androgen-sensitive to androgen-insensitive, we established an androgen-insensitive cell line similar to NEPC by treating LNCaP cells with enzalutamide for 30 days. Morever, we overexpressed PAX6 in LNCaP cells. Besides, we established DU145_shPAX6 cell lines to investigate whether PAX6 knockdown could repress the neuroendocrine transdifferentiation of NE-like cells. We then performed gene expression profiling analyzing data obtained from RNA-seq of  LNCAP, LNCAP_ENZ, DU145-shCon and DU145_shPAX6 cells. We also performed ATAC seq to explore  the chromatin accessibility in LNCaP_oePAX6, LNCaP_oeSTAT5A compared with LNCaP_con cells.