Loss of VHL-mediated pRb regulation promotes clear cell renal cell carcinoma

Abstract

The von Hippel-Lindau (VHL) tumor suppressor is a component of E3 ubiquitin ligase complexes that target cellular substrates for proteasome-mediated degradation. VHL inactivation by genetic aberrations is observed in most sporadic cases of clear cell renal cell carcinoma (ccRCC). VHL loss leads to constitutive stabilization of E3 ligase targets, including hypoxia inducible factor (HIF), in VHL-associated tumors. HIF stabilization upon VHL loss promotes transactivation of hypoxia responsive genes, which contributes to ccRCC development. However, several HIF-independent VHL targets have also been implicated in the promotion of tumorigenesis. Using proximity labeling to identify proteasomal VHL interactors, we identified retinoblastoma protein (pRb) as a novel substrate of VHL. Mechanistically, VHL interacts with pRb in an oxygen-sensitive manner, promoting its ubiquitin-mediated degradation. Concordantly, VHL-inactivation results in pRb hyperstabilization. Functionally, the hyperstabilization of pRb in ccRCC promoted tumorigenesis in vitro and in mouse models. We also show that downstream transcriptional changes induced by pRb hyperstabilization may contribute to ccRCC tumor development. Together, our findings reveal a novel VHL-related pathway which can be therapeutically targeted to inhibit ccRCC tumor development.