SUZ12 and NF1 loss cooperate to enhance Ras transcriptional output and sensitize cancers to epigenetic therapies

The polycomb repressive complex 2 (PRC2) plays an oncogenic role in several cancers. However, loss-of-function mutations in PRC2 components have been detected in a subset of hematopoietic malignancies, suggesting that different epigenetic landscapes are required in different tumor types. In this study we provide genomic, cellular, and mouse modeling data to demonstrate that loss-of-function mutations in the polycomb gene, SUZ12, and NF1 cooperate in peripheral nervous system tumors, glioblastomas, and melanomas. NF1 encodes a Ras GTPase-activating protein and its loss triggers moderate levels of Ras activation. We show that SUZ12-loss enhances the effects of NF1 mutations, in part, by amplifying Ras transcriptional signatures. Moreover, SUZ12-loss triggers an epigenetic switch that confers sensitivity to combined bromodomain and MEK inhibitors in vivo. Collectively these studies demonstrate an unexpected role for polycomb group genes in NF1 mutant tumors and reveal an epigenetic-based therapeutic strategy that may be exploited for a variety of cancers. 9 samples in triplicates, 3x LacZ control, 3x SUZ12 over expression, 3x JQ1 treatment