Lineage specific chromatin modification guides Pax5 mediated gene expression in neuroendocrine like differentiation of prostate cancer (ATAC-Seq)

Neuroendocrine-like differentiation of castration-resistant prostate cancer is highly aggressive and independent of the androgen receptor signaling for its progression. During such lineage differentiation, adenocarcinoma adopts basal and neuronal characteristics that alter its clinical progression, limiting its therapeutic opportunities. Inadequate understanding of the molecular mechanism for such transformation also restricts its targeted therapies. Using ATAC-Seq, acetylated-histone ChIP-seq, and RNA-seq, we have characterized the early transformation process and identified chromatin occupancy and gene expression differences between adenocarcinoma and neuroendocrine-like cancer cells. By comparing differentially active promoter signatures during lineage-specific transcriptional events, our results indicate that the transcription factor Pax5 plays a major role in the trans-differentiation processes. Using LuCaP PDX tissues and metastatic prostate cancer TMA, in conjunction with patient RNA-expression databases, we validated that Pax5 is selectively expressed only in neuroendocrine like cancer but not in adenocarcinoma. Further analysis reveals that Pax5 expression is involved in neuronal gene expression and critical for imparting therapy resistance. Further, our results indicate that increased hydroxymethylation at the Pax5 promoter leads to recruitment of the homeobox transcription factor Pbx1 for Pax5 transcription. This is in line with our findings that lineage-specific expression of Pbx1/Pax5 is associated with the development of neuroendocrine-like differentiation. Our study suggests, upon continuous exposure to anti-androgen therapeutic stress, chromatin modifications are associated with Pax5-mediated gene expression to adopt neuroendocrine-like characteristics of advanced prostate cancer.