Comprehensive mutational analysis of the VHL gene in sporadic renal cell carcinoma: Relationship to clinicopathological parameters

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Abstract
To delineate more precisely the somatic von Hippel‐Lindau disease (VHL) gene alteration as well as to elucidate its etiologic role in renal tumorigenesis, we examined a total of 240 sporadic renal cell carcinomas (RCCs) for somatic VHL gene alterations by DNA‐SSCP followed by sequencing, methylation‐specific PCR assay, microsatellite LOH study, and Southern blot analysis. Intragenic mutation of the VHL gene was found exclusively in clear‐cell or variant‐type RCCs at a frequency of 51% (104/202). Hypermethylation of the VHL promoter region was detected in an additional 11 clear‐cell RCCs. Microsatellite analysis demonstrated that LOH of the VHL locus was found in 140/155 (90%) informative clear‐cell RCCs. The VHL gene therefore seems to be inactivated in a two‐hit manner by intragenic mutation or hypermethylation plus allelic loss in clear‐cell RCC. Genomic rearrangement of the VHL gene detected by Southern analysis was not found (0/216 cases); this is in contrast to germ lines in which Southern aberrations consisted of 7–19% of the mutations. Clinicopathologic data demonstrated that VHL mutation/LOH did not vary according to tumor progression in clear‐cell RCC, including tumor diameter, stage, grading, distant metastasis, and lymph node metastasis. Interestingly, VHL mutation was significantly less frequent in RCCs occurring in younger (≦ 55 years) than that in older (≧ 56 years) patients. These data suggested that the inactivation of the VHL tumor‐suppressor gene is a specific genetic change in clear‐cell RCC, and that it may occur at an early or first step in the clear‐cell tumorigenic pathway rather than as a late event.