Abstract 957: Aurora kinase and N-myc are involved in neuroendocrine differentiation of prostate cancer and are new drug targets

Abstract

Abstract Background: Neuroendocrine prostate cancer (NEPC) is an aggressive variant of prostate cancer that can arise de novo or from existing prostate adenocarcinoma (PCA), and is promoted by the use of androgen deprivation therapy. We sought to better understand the molecular transformation of NEPC and identify new drug targets. Methods: Using Next Generation RNA sequencing and oligonucleotide arrays, we profiled NEPC, PCA, and benign prostate (BEN), and validated findings on tumors from a large cohort of patients using IHC and FISH. Functional studies were performed using NCI-H660 (NEPC), VCaP and LnCaP (PCA), RWPE (BEN) cell lines and xenografts. Results: There was a spectrum of NEPC, ranging from pure NEPC to those with mixed features of PCA and NEPC. ERG rearrangement was detected by FISH break-apart in 47% of NEPC, but ERG protein expression by IHC was absent and corresponded directly with lack of androgen receptor expression. We sequenced 7 NEPC, 30 PCA, 5 BEN. There were significant molecular differences between NEPC and PCA, with 936/25932 genes differentially expressed (P<0.001). The cell cycle kinases Aurora kinase A and B (AURKA, AURKB) were overexpressed in NEPC, and notably this was independent of cell proliferation (Ki67 expression). N-myc (MYCN), a gene frequently amplified in neuroblastoma, was overexpressed in NEPC (P<0.001), and both AURKA and MYCN were amplified. Using IHC and FISH, we validated these findings on a large cohort (30 BEN, 118 PCA, 30 NEPC) and found majority (>80%) of NEPC showed Aurora kinase A and B overexpression, and 35% harbored AURKA and co-existent MYCN amplification. A small subset of PCA (5%) and no BEN were positive. Transfection of MYCN induced AURKA expression as well as Aurora kinase activity in RWPE in vitro, and AURKA could also induce MYCN expression. MYCN and AURKA independently induced expression of the neuroendocrine (NE) markers, SYP and NSE. After validating NCI-H660 as model of NEPC, we observed enhanced in vitro and in vivo sensitivity to the Aurora kinase inhibitor PHA-739358 compared to LnCaP and VCaP, with > 50% tumor shrinkage in NEPC xenografts and minimal to no effect in PCA. Phosphorylated histone 3 expression, a downstream marker of Aurora kinase activity, was significantly inhibited in the treated NCI-H660 but not in treated PCA xenografts. Notably, NE marker expression was completely 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. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 957. doi:10.1158/1538-7445.AM2011-957