Improved Identification of von Hippel-Lindau Gene Alterations in Clear Cell Renal Tumors

Abstract

Purpose: To provide a comprehensive, thorough analysis of somatic mutation and promoter hypermethylation of the von Hippel-Lindau (VHL) gene in the cancer genome, unique to clear cell renal cancer (ccRCC). Identify relationships between the prevalence of VHL gene alterations and alteration subtypes with patient and tumor characteristics. Experimental Design: As part of a large kidney cancer case-control study conducted in Central Europe, we analyzed VHL mutations and promoter methylation in 205 well-characterized, histologically confirmed patient tumor biopsies using a combination of sensitive, high-throughput methods (endonuclease scanning and Sanger sequencing) and analysis of 11 CpG sites in the VHL promoter. Results: We identified mutations in 82.4% of cases, the highest VHL gene mutation prevalence reported to date. Analysis of 11 VHL promoter CpG sites revealed that 8.3% of tumors were hypermethylated and all were mutation negative. In total, 91% of ccRCCs exhibited alteration of the gene through genetic or epigenetic mechanisms. Analysis of patient and tumor characteristics revealed that certain mutation subtypes were significantly associated with Fuhrman nuclear grade, metastasis, node positivity, and self-reported family history of RCC. Conclusion: Detection of VHL gene alterations using these accurate, sensitive, and practical methods provides evidence that the vast majority of histologically confirmed ccRCC tumors possess genetic or epigenetic alteration of the VHL gene and support the hypothesis that VHL alteration is an early event in ccRCC carcinogenesis. These findings also indicate that VHL molecular subtypes can provide a sensitive marker of tumor heterogeneity among histologically similar ccRCC cases for etiologic, prognostic, and translational studies.Considerable progress has been made in understanding the genetic basis of kidney cancer (1, 2). The susceptibility genes associated with several forms of inherited renal cell cancer (RCC) have been identified by rigorous analysis of families using genetic linkage analysis and positional cloning (3 -7). The most common subtype of RCC is the conventional clear cell type (ccRCC), which accounts for f75% of cases. In both familial and sporadic ccRCC, allelic inactivation of the von

Clear-cell papillary renal cell carcinoma: molecular and immunohistochemical analysis with emphasis on the von Hippel–Lindau gene and hypoxia-inducible factor pathway-related proteins

“…Silencing of the VHL gene via mutations is common in sporadic clear-cell RCC having been documented in 37-80% of cases depending on the methods used. 17 In our series, none of the clear-cell papillary RCC cases harbored VHL mutations, whereas four mutations of the VHL gene were seen in three clear-cell RCCs (27%). Sequencing of matched normal kidney samples confirmed that these mutations were somatic and only changes that would result in an amino-acid change were counted as mutations in this study.…”

“…All of the mutations seen in our clear cell RCC have been described previously in the literature and are predicted to result in a nonfunctional/dysfunctional VHL protein product. 17 The low incidence of VHL mutations seen in clearcell RCC may in part reflect the sample size or the sequencing methods used.…”

“…1,14 Over the years, numerous studies have documented somatic mutations and promoter hypermethylation of the VHL gene as well as losses of chromosome 3p in sporadic clear-cell RCC, and such alterations have become defining characteristics of these tumors. 1,[15][16][17] The VHL gene product regulates transcription of several genes through the hypoxia-inducible factor (HIF) pathway. 18 Silencing of VHL expression ultimately results in overexpression of a number of proteins, including HIF-1a, glucose transporter-1 (GLUT-1), and CA9.…”

CSF1R copy number changes, point mutations, and RNA and protein overexpression in renal cell carcinomas

“…2 As germline VHL mutations underlie the von Hippel-Lindau syndrome and VHL somatic mutations are found in most sporadic clear cell renal cell carcinomas, this gene is considered the most relevant target of the recurrent 3p deletion seen in this tumor type. 3,4 On the other hand, no target genes have been identified for the 5q22qter gain, the second most common chromosome aberration in clear cell renal cell carcinomas. We therefore tested whether two potential oncogenes mapping to that chromosomal region, CSF1R and PDGFRB, could be the relevant target genes of the recurrent 5q gain.…”

“…In fact, germline mutations of VHL underlie the von Hippel-Lindau syndrome (which includes clear cell renal cell carcinoma as one of its features), whereas somatic inactivation of this gene has been demonstrated in the great majority of sporadic clear cell renal cell carcinomas. 3,4 On the other hand, no target genes have been identified for the 5q22qter gain, the second most common copy number change in clear cell renal cell carcinomas. 2,5 The colony-stimulating factor-1 receptor (CSF1R) gene located in 5q33 is a potential target for this chromosomal gain in clear cell renal cell carcinomas.…”