Genomic organization and chromosomal localization of the human CUL2 gene and the role of von Hippel-Lindau tumor suppressor-binding protein (CUL2 andVBPI) mutation and loss in renal-cell carcinoma development

Germline mutations in the von Hippel-Lindau (VHL) disease tumor suppressor gene (TSG) convey a high risk of clear-cell renal-cell carcinoma (CC-RCC) a nd most sporadic CC-RCCs demonstrate somatic inactivation of the VHL TSG, H owever, the existence of further CC-RCC gatekeeper genes is implied by CC-R CC kindreds not linked to the VHL gene and the absence of somatic VHL inact ivation in similar to 30% of sporadic CC-RCC, Genes that encode proteins wh ich interact with the VHL gene product (VHL) provide candidate gatekeeper R CC genes. VHL forms a multimeric complex with two subunits (B and C) of the SIII (elongin) transcriptional elongation complex and CUL2, a member of th e cullin family. Most pathogenic VHL mutations inhibit formation of the VHL /elonginB+C/CUL2 complex. A further VHL-binding protein of unknown function , VBPI, fails to bind to truncated forms of VHL. We have investigated the p ossible roles of CUL2 and VBPI in renal tumorigenesis by analyzing sporadic RCC of known VHL mutation or hypermethylation status, including CC-RCC wit hout VHL inactivation (n = 40); CC-RCC with VHL inactivation (n = 35); and non-CC-RCC (n = 14). No VBPI mutations were identified in 89 sporadic RCCs, suggesting that VBPI is not an RCC gatekeeper gene. To investigate CUL2, w e mapped the CUL2 gene to chromosome band 10p 11.1-p11.2, a region reported to show loss of heterozygosity (LOH) in several human cancers (including n on-CC-RCC); determined the genomic organization; and performed mutation ana lysis of the 21 exons identified, Using novel intragenic polymorphisms, we detected LOH in 6/25 informative RCCs; however, no pathogenic CUL2 mutation s were identified in the 89 RCCs analyzed. These findings suggest that unle ss CUL2 is inactivated by epigenetic events, it is not a major RCC TSG, How ever, CUL2 remains a candidate TSG for other tumor types demonstrating 10p LOH. (C) 1999 Wiley-Liss, Inc.