MCPIP1 Downregulation in Clear Cell Renal Cell Carcinoma Promotes Vascularization and Metastatic Progression.

Clear cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer and it forms highly vascularized tumors. The monocyte endoribonuclease MCPIP1 negatively regulates inflammation by degrading mRNA encoding proinflammatory cytokines, such as IL6, IL1, and IL12. MCPIP1 is also a negative regulator of NFκB and AP1 activity and it influences a broad range of miRNA activities. Here we report that MCPIP1 protein levels are decreased during renal cancer progression. In patient-derived tumors and xenografts established in NOD-SCID or nude mice, low MCPIP1 levels correlated strongly with increased proliferation, tumor outgrowth, and vascularity. MCPIP1 activity regulated secretion of VEGF, IL8, and CXCL12 leading to chemotaxis of microvascular endothelial cells, phosphorylation of VE-cadherin, and increased vascular permeability. Mechanistic investigations showed that MCPIP1 regulated ccRCC cell motility, lung metastasis, and mesenchymal phenotype by regulating key elements in the EMT signaling axis. Overall, our results illuminate how MCPIP1 serves as a key nodal point in coordinating tumor growth, angiogenesis, and metastatic spread in ccRCC. Cancer Res; 77(18); 4905-20. ©2017 AACR. ©2017 American Association for Cancer Research.