The von Hippel-Lindau tumor suppressor protein sensitizes renal cell carcinoma cells to tumor necrosis factor-induced cytotoxicity by suppressing the nuclear factor-kappaB-dependent antiapoptotic pathway.

Functional inactivation of the von Hippel-Lindau (VHL) tumor suppressor protein pVHL is the cause of the familial VHL disease and the majority of sporadic renal clear cell carcinomas (RCCs). RCCs pose a significant problem for conventional cancer treatment protocols because of their highly recalcitrant characteristics to radio- and/or chemotherapies. In fact, the leading cause of morbidity and mortality of VHL patients is RCC. Recently, global gene profiling of RCC cells has revealed that sensitivity to tumor necrosis factor (TNF)-alpha-mediated cytotoxicity is pVHL dependent. Here, we report that although RCC cells devoid of functional pVHL (RC3) were resistant to the cytotoxic effects of TNF-alpha, reconstitution of these RCC cells with wild-type pVHL (WT8) restored their sensitivity to TNF-alpha cytotoxicity. The major TNF-alpha-inducible transcription factor nuclear factor (NF)-kappaB in the nuclear fraction capable of binding NF-kappaB-binding motifs was significantly increased in RC3 cells. Concordantly, the expression of NF-kappaB-target antiapoptotic genes c-FLIP, Survivin, c-IAP-1, and cIAP-2, which block the activities of caspases 8 and 3, were dramatically elevated in RC3 cells. Indeed, RC3 cells showed low caspases 8 and 3 activities. These results demonstrate that pVHL facilitates TNF-alpha-induced cytotoxicity in RCC cells, at least in part, through the down-regulation of NF-kappaB activity and subsequent attenuation of antiapoptotic proteins c-FLIP, Survivin, c-IAP-1, and c-IAP-2.