Molecular characterization of neuroendocrine prostate cancer (NEPC) and identification of new drug targets.

Abstract

19 Background: NEPC is an aggressive variant of prostate cancer that can arise de novo or from existing prostate adenocarcinoma (PCA). We sought to better understand the molecular transformation of NEPC and identify new drug targets. Methods: We used Next Generation RNA sequencing and oligonucleotide arrays to profile 7 NEPC, 30 PCA, 5 benign prostate (BEN), and validated findings on tumors from a large cohort of patients (30 NEPC, 118 PCA, 30 BEN) using IHC and FISH. Functional studies were performed using NCI-H660 (NEPC), VCaP and LnCaP (PCA), RWPE (BEN). Results: ERG rearrangement was present in 47% of NEPC, but ERG protein expression was absent and corresponded directly with lack of AR expression. 936/25932 genes were differentially expressed in NEPC versus PCA (P<0.001). Aurora kinases (AURKA, AURKB) and N-myc (MYCN) were overexpressed in NEPC (P<0.001) and AURKA and MYCN amplified. Using IHC and FISH, we validated these findings on a large cohort and found majority (>80%) of NEPC showed Aurora overexpression, 35% had AURKA and MYCN amplification. A small subset of PCA (5%) and no BEN were positive. Transfection of MYCN induced AURKA expression and kinase activity in vitro, and MYCN or AURKA could induce expression of neuroendocrine (NE) markers (SYP, NSE). After validating NCI-H660 as model of NEPC, we observed dramatic and enhanced in vitro and in vivo sensitivity to the Aurora kinase inhibitor PHA-739358 in NCI-H660 compared to minimal to no effect in LnCaP and VCaP. Phospho-H3 expression, a downstream marker of Aurora kinase activity, was inhibited in the treated NCI-H660 and not in PCA. Notably, NE marker expression was also suppressed in the treated NCI-H660 xenografts, again supporting a role of Aurora kinase in modulating the NE phenotype. Conclusions: There is likely clonal origin of NEPC from PCA (with ERG fusion positivity seen in both), but ERG expression is limited to PCA and driven by AR signaling. We discovered significant overexpression and gene amplification of Aurora kinases and N-myc in NEPC and a small subset of PCA, and evidence that that they cooperate and induce a NE phenotype in prostate cells. In vitro and in vivo data confirms that these are novel drug targets for NEPC. No significant financial relationships to disclose.