Constitutional and somatic mutations in the WTI gene in wilms' tumor patients

Whdlms' tumor development, like most tumors, involves multiple genetic alterations affecting divershd genes. Only one of these has thus far been identified, the Wilms' tumor I ( WTI ) gene on 11p 13, which functions as a tumor suppressor gene. We assessed the involvement of the WTI gene constitutionally and somatically in 26 Wilms' tumor patients. Of these, the clinical data suggest a constitutional pre‐disposition in 12 bilateral cases and 7 cases with early onset. We employed Southern blot analysis and PCR‐based markers for analyses of somatic allelic losses in chromosome bands 11 p 13, 11 p 15 and 16q and screened for point mutations in exons 2–10 of the WTI gene with denaturing gradient gel electrophoresis (DGGE). Of the 12 cases with multiple tumors, I exhibited a constitutional 11 p 13 deletion and a somatic stop mutation in exon 4 of the WTI gene and 2 harbored constitutional mutations in the WTI gene: a pre‐mature stop codon in exon 6 in a boy with bilateral cryptorchidism and bilateral Wilms' tumors and an intragenic deletion in a girl with bilateral WT. Three additional bilateral tumors displayed WTI rearrangements or allelic losses with 11 p 13 markers. Four of 7 patients with an early onset of unilateral tumor had losses of 11p 13, though no WTI mutations were detected. Two of the remaining cases that did not show any somatic or constitutional 11 p 13 alterations had Beckwith‐Wiedemann syndrome, known to involve the 11 p 15 region.