VHL gene alterations in renal cell carcinoma patients: novel hotspot or founder mutations and linkage disequilibrium

Abstract

Mutations in the von Hippel-Lindau (VHL) gene are frequently detected in human sporadic renal cell carcinoma (RCC). We analysed 102 Swedish RCCs for VHL mutations by PCR–SSCP and sequencing. In 47 patients (46.1%), 70 different mutations were found, and most of them represented novel variations of the VHL gene. Mutations in the VHL gene were found in 54% of clear cell renal cell carcinomas (CCRCC) and in 18% of chromophilic cancers but in no chromophobe cancers or oncocytomas (P=0.016). Three novel hotspot or founder mutations were detected in our study: four CCRCCs carried a missense mutation (glutamic acid to lysine) at codon 160 which is critical in the stabilization of the H1 helix of the α domain and the α-β domain interface in the VHL protein. Five CCRCCs and one chromophilic RCC harbored a 15-nucleotide in-frame deletion (codons 41–45) at a duplex tandem repeat sequence site. Moreover, this deletion was in linkage disequilibrium with a C→T transition in the promoter region. The frequency of linkage was 17 times more common than chance. Five patients with this linked mutation resided in the same hospital district and at least three of them showed the two sequence variants in the tumor-adjacent tissue. In 5/6 patients the wild-type allele was lost in the tumor samples, suggesting a causal role for the mutations in RCC. These linked mutations might be novel polymorphisms maintained in a relative isolated population. Multiple mutations in VHL were found in 17 tumors out of 47 tumors with the VHL mutation. A higher multiple mutation detected rate (33%) was observed in grade 3 CCRCCs than those in grade 1 (22%) and grade 2 (9%) (P=0.04). This is evidence on the association between VHL mutation and extent of nuclear atypia.