Analysis of WT1 genes in two cases with bilateral Wilms' tumor

WT1 gene, located at 11 p13, is considered as the tumor suppresser gene of Wilms' tumor. We report the result of analysis of WT1 genes in two children with bilateral Wilms' tumors (BWT). Case 1 is an 1-year-old girl with an aniridia and a mental retardation. A hemi-deletion of the short arm of chromosome 11 was recognized as a germ line mutation (WAR syndrome). The analysis of WT1 gene revealed that the homo-deletion of right tumor, and 30bp deletion and 5bp insertion in exon 7, resulting in arising stop codon at exon 9, in addition to hemi-deletion of left tumor were detected, respectively. The histology of bilateral tumors was nephroblastoma, nephroblastic type. Case 2 patient is a 6-months-old boy. No abnormality of WT1 gene in bilateral tumors was found. The histology of bilateral tumors was nephroblastoma, nephroblastic type. The type of the WT1 gene mutation in the left tumor of the case 1 in the present study, to our knowledge, is not present in the mutation types reported previously. These findings suggest that the inactivations of WT1 genes in both alleles generate Wilms' tumor in bilateral tumors in case 1, furthermore, demonstrating that the bilateral tumors arise from different origins, although the bilateral tumors of case 1 showed the same findings of histology. The relation between subtype of the mutation and the histological finding requires further examination.