Individuals who inherit one faulty von Hippel-Lindau gene (VHL) allele are predisposed to VHL disease, which is characterized by the development of cerebellar, spinal, and retinal hemangioblastoma, pheochromocytoma, and clear-cell renal cell carcinoma (CC-RCC) (29). The tumor develops upon the somatic loss of the remaining wild-type VHL allele in a susceptible cell. Importantly, biallelic loss of VHL is associated with the vast majority of sporadic CC-RCCs, establishing VHL as a critical suppressor of renal oncogenesis (29). CC-RCC is resistant to conventional radiation and chemotherapies, and approximately one-quarter of renal cancer patients present with advanced disease, including locally invasive or metastatic CC-RCC (12). Unfortunately, one-third of patients who undergo surgical removal of localized tumors have recurrence of the disease, and the median survival for patients harboring metastatic CC-RCC is 13 months (12). Moreover, the principal cause of morbidity and death of VHL patients is CC-RCC (29). Despite the need to better understand the aggressive nature of CC-RCC, the molecular pathways governing its malignant phenotype remain unresolved.The most well-characterized function of VHL is as a substrate-recognition component of the SCF (Skp1/Cdc53/F-box protein)-like E3 ubiquitin ligase complex called ECV (elongins/Cul2/VHL) that selectively ubiquitylates oxygen-dependent prolyl-hydroxylated ␣ subunits of hypoxia-inducible factor

The tumor suppressor function of the von HippelLindau protein (pVHL) has previously been linked to its role in regulating hypoxia-inducible factor levels. However, VHL gene mutations suggest a hypoxia-inducible factor-independent function for the N-terminal acidic domain in tumor suppression. Here, we report that phosphorylation of the N-terminal acidic domain of pVHL by casein kinase-2 is essential for its tumor suppressor function. This post-translational modification did not affect the levels of hypoxia-inducible factor; however, it did change the binding of pVHL to another known binding partner, fibronectin. Cells expressing phospho-defective mutants caused improper fibronectin matrix deposition and demonstrated retarded tumor formation in mice. We propose that phosphorylation of the acidic domain plays a role in the regulation of proper fibronectin matrix deposition and that this may be relevant for the development of VHL-associated malignancies.

The loss of functional von Hippel-Lindau (VHL) tumor suppressor gene is associated with the development of clear-cell renal cell carcinoma (CC-RCC). Recently, VHL was shown to promote the transcription of E-cadherin, an adhesion molecule whose expression is inversely correlated with the aggressive phenotype of numerous epithelial cancers. Here, we performed immunohistochemistry on CC-RCC tissue microarrays to determine the prognostic value of E-cadherin and VHL with respect to Fuhrman grade and clinical prognosis. Low Fuhrman grade and good prognosis associated with positive VHL and E-cadherin immunoreactivity, whereas poor prognosis and high-grade tumors associated with a lack of E-cadherin and lower frequency of VHL staining. A significant portion of CC-RCC with positive VHL immunostaining correlated with nuclear localization of C-terminally cleaved E-cadherin. DNA sequencing revealed in a majority of nuclear E-cadherin-positive CC-RCC, subtle point mutations, deletions and insertions in VHL. Furthermore, nuclear E-cadherin was not observed in chromophobe or papillary RCC, as well as matched normal kidney tissue. In addition, nuclear E-cadherin localization was recapitulated in CC-RCC xenografts devoid of functional VHL or reconstituted with synthetic mutant VHL grown in SCID mice. These findings provide the first evidence of aberrant nuclear localization of E-cadherin in CC-RCC harboring VHL mutations, and suggest potential prognostic value of VHL and E-cadherin in CC-RCC. [4][5][6][7] Currently, a prediction of patient survival is based on traditional clinical parameters, including tumor size and Fuhrman nuclear grade. 8 However, the emerging understanding of the molecular pathways implicated in CC-RCC genesis and progression is providing previously unappreciated markers, which may serve as additional or better prognostic indicators of CC-RCC.The principal cause of sporadic CC-RCC and familial von Hippel-Lindau (VHL) disease-associated CC-RCC is the inactivating mutations of VHL. Although VHL patients also develop tumors in other organs including the central nervous system, retina and the adrenal gland, CC-RCC remains to be the leading cause of morbidity and death for VHL patients. 9 The most well-established function of VHL is its role in the oxygen-dependent negative regulation of hypoxia-inducible factor (HIF). VHL is a substrate-conferring component of an E3 ubiquitin ligase ECV (elongins/Cul2/VHL) that polyubiquitylates the catalytic a-subunit of HIF that has undergone hydroxylation on conserved prolyl residues within the oxygen-dependent degradation (ODD) domain. Prolyl hydroxylation is mediated by a class of prolyl hydroxylases (PHD1-3) in an oxygen-dependent manner. Thus, under hypoxia or in the absence of a functional VHL, HIFa becomes stabilized and binds to its common and constitutively expressed b-subunit, forming an active HIF transcription factor capable of transactivating numerous hypoxia-inducible genes such as vascular endothelial growth factor (VEGF),

von Hippel-Lindau (VHL) tumor suppressor protein—inactivated in VHL disease and sporadic kidney cancer—is a component of an E3 ubiquitin ligase complex that selectively ubiquitinates the α subunit of the hypoxia-inducible factor (HIF) transcription factor for subsequent destruction by the 26S proteasome. Here, we report the identification and characterization of the first VHL homologue, VHL-like protein (VLP), located on chromosome 1q21.2. A 676-bp partial cDNA encoding a 139-amino acid protein that is 78% similar to VHL was isolated by reverse transcription-PCR from human brain cerebellum and several cancer cell lines. The expression of VLP transcript is most abundant in the placenta. Like VHL, VLP contains a β domain capable of binding HIFα. However, unlike VHL, it does not contain a recognizable α domain, which is required for nucleating the multiprotein E3 ubiquitin ligase complex. The increased expression of VLP in the presence of VHL attenuated the ubiquitination of HIFα and led to the accumulation of downstream HIF target genes. These results taken together indicate that VLP functions as a dominant-negative VHL to serve as a protector of HIFα.

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