An oncogene-tumor suppressor cascade drives metastatic prostate cancer by coordinately activating Ras and nuclear factor-κB

Metastasis is a fatal complication of prostate cancer, but its mechanisms remain largely unknown. In this report, the authors identify a signaling pathway commonly deregulated in human prostate cancer and describe how it can foster both primary growth and metastatic tumor progression. Epigenetic silencing of the RasGAP DAB2IP by EZH2 overexpression results in aberrant activation of Ras signaling, but also of NF-κB. These two events are mediated by different DAB2IP domains and have distinct roles in localized growth and distant dissemination. Metastasis is responsible for the majority of prostate cancer–related deaths; however, little is known about the molecular mechanisms that underlie this process. Here we identify an oncogene–tumor suppressor cascade that promotes prostate cancer growth and metastasis by coordinately activating the small GTPase Ras and nuclear factor-κB (NF-κB). Specifically, we show that loss of the Ras GTPase-activating protein (RasGAP) gene DAB2IP induces metastatic prostate cancer in an orthotopic mouse tumor model. Notably, DAB2IP functions as a signaling scaffold that coordinately regulates Ras and NF-κB through distinct domains to promote tumor growth and metastasis, respectively. DAB2IP is suppressed in human prostate cancer, where its expression inversely correlates with tumor grade and predicts prognosis. Moreover, we report that epigenetic silencing of DAB2IP is a key mechanism by which the polycomb-group protein histone-lysine N -methyltransferase EZH2 activates Ras and NF-κB and triggers metastasis. These studies define the mechanism by which two major pathways can be simultaneously activated in metastatic prostate cancer and establish EZH2 as a driver of metastasis.