NF-κ-Dependent Plasticity of the Epithelial to Mesenchymal Transition Induced by Von Hippel-Lindau Inactivation in Renal Cell Carcinomas

The critical downstream signaling consequences contributing to renal cancer as a result of loss of the tumor suppressor gene von Hippel-Lindau (VHL) have yet to be fully elucidated. Here, we report that VHL loss results in an epithelial to mesenchymal transition (EMT). In studies of paired isogenic cell lines, VHL silencing increased the levels of N-cadherin and vimentin and reduced the levels of E-cadherin relative to the parental VHL(+) cell line, which displayed the opposite profile. VHL(+) cells grew as clusters of cuboidal and rhomboid cells, whereas VHL-silenced cells took on an elongated, fibroblastoid morphology associated with a more highly invasive character in Matrigel chamber assays. Based on earlier evidence that VHL loss can activate NF-kappa B, a known mediator of EMT, we tested whether NF-kappa B contributed to VHL-mediated effects on EMT. On pharmacologic or molecular inhibition of NF-kappa B, VHL-silenced cells regained expression of E-cadherin, lost expression of N-cadherin, and reversed their highly invasive phenotype. Introducing a pVHL-resistant hypoxia-inducible factor 1 alpha (HIF1 alpha) mutant (HIF alpha(M)) into VHL(+) cells heightened NF-kappa B activity, phenocopying EMT effects produced by VHL silencing. Conversely, inhibiting the heightened NF-kappa B activity in this setting reversed the EMT phenotype. Taken together, these results suggest that VHL loss induces an EMT that is largely dependent on HIF alpha-induced NF-kappa B. Our findings rationalize targeting the NF-kappa B pathway as a therapeutic strategy to treat renal tumors characterized by biallelic VHL inactivation. Cancer Res; 70(2); 752-61. (C)2010 AACR.