von Hippel-Lindau Tumor Suppressor Protein and Hypoxia-Inducible Factor in Kidney Cancer

The development of hereditary von Hippel-Lindau (VHL) disease and the majority of sporadic kidney cancers are due to the functional inactivation of the VHL gene. The product of the VHL gene, pVHL, in association with elongins B and C, cullin 2, and Rbx1 form an E3 ubiquitin-ligase complex VEC that targets the alpha subunits of hypoxia-inducible factor (HIF) for ubiquitination. Ubiquitin-tagged HIF-alpha proteins are subsequently degraded by the common 26S proteasome. pVHL functions as the substrate-docking interface that specifically recognizes prolyl-hydroxylated HIF-alpha. This hydroxylation occurs only in the presence of oxygen or normoxia. Thus, under hypoxia, HIF-alpha subunits are no longer subjected to degradation and are thereby able to dimerize with the common and constitutively stable beta subunits. The heterodimeric HIFs upregulate a myriad of hypoxia-inducible genes, triggering our physiologic response to hypoxia. Inappropriate accumulations of HIF-alpha in VHL disease are believed to contribute to the pathogenesis via the upregulation of several of these HIF target genes. Our current molecular understanding of the roles of HIF and pVHL in the development of VHL-associated clear-cell renal cell carcinoma (CC-RCC) is the focus of this review.