472 Biochemical Society Transactions (2008) Volume 36, part 3 Role of the VHL (von Hippel–Lindau) gene in renal cancer: a multifunctional tumour suppressor Michelle J. Nyhan*, Gerald C. O’Sullivan† and Sharon L. McKenna* 1 *Leslie C. Quick Laboratory, Cork Cancer Research Centre, University College Cork, Cork, Ireland, and †Mercy University Hospital, Grenville Place, Cork, Ireland Abstract The VHL (von Hippel–Lindau) tumour-suppressor gene is inactivated in VHL disease and in sporadic cases of CCRCC [clear-cell RCC (renal cell carcinoma)]. pVHL (VHL protein) functions as part of an E3 ubiquitin ligase complex that targets proteins for proteasomal degradation. The best-characterized substrate is HIF- α (hypoxia-inducible factor-α). Loss of pVHL and subsequent up-regulation of HIF target genes has been attributed to the highly vascular nature of these neoplasms. However, pVHL does not just function as the executioner of HIF-α. Additional functions of pVHL that may be important in preventing CCRCC tumorigenesis have been identified, including primary cilium maintenance, assembly of the extracellular matrix and roles in the stabilization of p53 and Jade-1 (gene for apoptosis and differentiation in epithelia). Current evidence indicates that pVHL probably requires additional co-operating signalling pathways for CCRCC initiation and tumorigenesis. Introduction The familial cancer syndrome, VHL (von Hippel–Lindau) disease, occurs as a consequence of inheriting a mutation in the VHL tumour-suppressor gene located on chromosome locus 3p25 [1]. VHL disease follows the classical Knudson two-hit model of tumorigenesis as inactivation of the remaining copy of the VHL gene in somatic cells leads to the development of highly vascular and benign tumours. The predominant tumour manifestations include haemangio- blastomas of the central nervous system and retina, renal cysts and CCRCC [clear-cell RCC (renal cell carcinoma)] in the kidney, phaeochromocytomas and pancreatic cysts and tumours [2]. The VHL tumour-suppressor gene is also frequently inactivated in sporadic cases of CCRCC. Several studies have recently shown that VHL genetic alterations (VHL gene mutations or hypermethylation of the promoter region) together with LOH (loss of heterozygosity) at the VHL locus are common genetic events in sporadic cases of CCRCC. The reported incidence of somatic VHL gene mutations varies from 17.9 to 71% with hypermethylation of the promoter region of the VHL gene occurring in 5.5–20.4% of sporadic cases of CCRCC [3–5]. LOH has also been reported in up to 98% of sporadic CCRCC cases [6]. CCRCC is the predominant subtype of RCC and there are approx. 210 000 cases diagnosed worldwide each year Key words: clear-cell renal cell carcinoma, hypoxia-inducible factor (HIF), renal cancer, tumour suppressor, von Hippel–Lindau (VHL), von Hippel–Lindau protein (pVHL). Abbreviations used: aPKC, atypical protein kinase C; RCC, renal cell carcinoma; CCRCC, clear- cell RCC; COL4A2, collagen IV α2 chain; ECM, extracellular matrix; GLUT, glucose transporter; GSK3β, glycogen synthase kinase 3β; HIF, hypoxia-inducible factor; Jade-1, gene for apoptosis and differentiation in epithelia; LOH, loss of heterozygosity; MMP, matrix metalloproteinase; MT1-MMP, membrane type 1-MMP; TGF-α, transforming growth factor-α; VDU, VHL-interacting deubiquitinating enzyme; VEGF, vascular endothelial growth factor; VHL, von Hippel–Lindau; pVHL, VHL protein. 1 To whom correspondence should be addressed (email s.mckenna@ucc.ie). (GLOBOCAN 2002; available at http://www-dep.iarc.fr). RCC is an asymptomatic disease with approx. 25% of pa- tients presenting with advanced disease. The presence of metastatic disease results in a median survival time of approx. 13 months [7]. Consequently, there is a need to decipher fully the functions of the commonly mutated VHL tumour- suppressor gene in CCRCC tumorigenesis and therefore the focus of this mini-review is on current knowledge of the multifunctional roles of pVHL (VHL protein). pVHL’s role as an E3 ubiquitin ligase The VHL gene produces two proteins: pVHL 30 and pVHL 19 (collectively referred to as pVHL). Internal translation at codon 54 of the VHL mRNA generates pVHL 19 . Reintroduction of either pVHL 30 or pVHL 19 into VHL- defective RCC cell lines suppresses their ability to form tumours in nude mice. pVHL therefore acts as a tumour suppressor. The best-characterized role of pVHL is as the substrate recognition component of an E3 ubiquitin ligase complex that also contains elongin C, elongin B, Cul-2 and Rbx1. This complex targets proteins for ubiquitin- mediated degradation by the 26S proteasome. pVHL contains two functional domains: the α domain binds to elongin C and the β domain acts as the substrate-docking interface for target proteins. Several substrates of this E3 ubiquitin ligase complex have been identified. These include aPKCλ (atypical protein kinase Cλ), VDUs (VHL-interacting deubiquitinating enzymes; VDU-1 and VDU-2), and two subunits of RNA polymerase II (Rpb1 and Rpb7). However, the best-characterized target of this complex is the α-subunit of the HIF (hypoxia-inducible factor) family members, HIF- 1α, HIF-2α and HIF-3α (reviewed in [8]). pVHL’s regulation of HIF Regulation of the expression of HIF-α by the pVHL/E3 ubiquitin ligase complex is critical for the normal functioning C  The Authors Journal compilation C  2008 Biochemical Society Biochem. Soc. Trans. (2008) 36, 472–478; doi:10.1042/BST0360472