N-MYC in NEPC

Emerging observations from clinical trials for CRPC suggest that up to 30% of men eventually evolve or progress to a predominantly neuroendocrine phenotype. Neuroendocrine prostate cancer (NEPC) do not respond to hormonal intervention; they frequently metastasize to visceral organs, and carry a poor prognosis with an average survival of less than one year. Together with Drs. Himisha Beltran and Mark Rubin, we discovered significant over-expression and gene amplification of AURKA (encoding Aurora-A) and MYCN (chromosome 2p24, encoding N-Myc) in NEPC as compared to PCa. However, there is a spectrum of N-Myc expression in CRPC samples with 20% of CRPC tumors demonstrating transcript levels in the range of NEPC. We developed an in situ hybridization (RNAish) probe for MYCN mRNA expression and confirmed abundant levels of MYCN mRNA in NEPC tumor cells and in CRPC tumors with focal neuroendocrine differentiation (shown above, inset: chromogranin A IHC).   Consistent with neuroblastoma data, we found that these proteins form a complex that stabilizes N-Myc and that is targetable with allosteric Aurora-A inhibitors. We have generated novel pre-clinical models of N-Myc driven prostate cancer including genetically engineered mice that molecularly and histologically mimic clinical NEPC and that elucidated a novel transcription regulating complex between N-Myc and (Enhancer of Zeste Homolog 2) EZH2 in driving the NEPC phenotype (Dardenne et al. Cancer Cell, 2016). Our mouse N-Myc signature distinguished NEPC samples from CRPC samples from a large cohort of human prostate cancer samples based on pathological criteria, low AR signaling, and high Integrated NEPC score from a recently defined multi-gene molecular classifier of NEPC (Beltran et al. Nature Medicine, 2016)

The next phase of this project will be to biochemically and functionally characterize the driving role of the N-Myc/EZH2 complex and query the role of Aurora A in both prostate adenocarcinoma and NEPC.  For this, we have generated multiple preclinical models (human and mouse cell lines, organoids, genetically engineered mouse (GEM) models, xenografts and allografts) and are currently developing a new GEM that will allow for temporal control of N-Myc expression and cell lineage tracing and enrichment.