WT1: a novel tumor suppressor gene inactivated in Wilms' tumor

The development of Wilms' tumor, a pediatric kidney cancer, has been linked to the inactivation of a tumor suppressor gene both by epidemiologic studies and by genetic analyses. Like retinoblastoma, Wilms' tumors can occur bilaterally in individuals with apparent genetic susceptibility to this disease. This led Knudson and Strong to propose in 1972 that two genetic events were rate limiting in tumor development and that predisposed individuals had already inherited one mutation in the germline. The observation of karyotype abnormalities in predisposed children and studies of the molecular genetics of Wilms' tumor specimens enabled the identification of chromosome band 11p13 as one genetic locus inactivated in Wilms' tumor. The recent isolation of the WT1 gene, which is the specific target within that locus, offers new insight into the etiology of Wilms' tumor. This gene has properties distinct from those of other known tumor suppressor genes. WT1 encodes a zinc finger transcription factor that is alternatively spliced and has high sequence homology to the early growth response genes (EGR). Unlike the retinoblastoma (RB1) and p53 genes that are expressed ubiquitously, WT1 is expressed in specific cells of the kidney and only during a short period in development. Thus, disruption of a gene that is active during a critical period in the development of a specific organ can lead to neoplastic growth in that organ. Future studies are aimed at exploring the link between the role of the WT1 gene in normal development and in tumorigenesis of the kidney.