Targeting the MYCN-PARP-DNA Damage Response Pathway inNeuroendocrine Prostate Cancer

Purpose: We investigated MYCN-regulated molecular pathways in castration-resistant prostate cancer (CRPC) classified by morphological criteria as adenocarcinoma or neuroendocrine to extend the molecular phenotype, establish driver pathways, and identify novel approaches to combination therapy for NEPC. Results: Using comparative bioinformatics analyses of CRPC-Adeno and CRPC-Neuro RNA sequence data from public datasets and a panel of 28 PDX models we identified a MYCN-PARP-DNA damage response (DDR) pathway that is enriched in CRPC with neuroendocrine differentiation (NED) and CRPC-Neuro. ChIP-PCR assay revealed that N-MYC transcriptionally activates PARP1, PARP2, BRCA1, RMI2, and TOPBP1 through binding to the promoters of these genes. MYCN or PARP1 gene knockdown significantly reduced the expression of MYCN-PARP-DDR pathway genes and NED markers, and inhibition with MYCNsi and/or PARPsi, BRCA1si, or RMI2si significantly suppressed malignant activities including cell viability, colony formation and cell migration in C4-2b4 and NCI-H660 cells. Targeting this pathway with AURKA inhibitor PHA739358 and PARP inhibitor olaparib generated similar therapeutic effects to gene knockdown in vitro and significantly suppressed tumor growth in both C4-2b4 and MDA PDX144-13C subcutaneous models in vivo. Conclusions: Our results identify a novel MYCN-PARP-DDR pathway that is driven by N-MYC in a subset of CRPC-Adeno and in NEPC. Targeting this pathway using in vitro and in vivo CRPC-Adeno and CRPC-Neuro models demonstrated a novel therapeutic strategy for NEPC. Further investigation of N-MYC-regulated DDR gene targets and the biological and clinical significance of MYCN-PARP-DDR signaling will more fully elucidate the importance of the MYCN-PARP-DDR signaling pathway in the development and maintenance of NEPC.

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