Germline and somatic abnormalities of chromosome 7 in Wilms' tumor.

Although a gene (WT1) located at chromosome 11p13 is implicated in the development of Wilms' tumor (WT), there is evidence that genes on other chromosomes are also involved. A WT patient presented with a constitutional balanced translocation between chromosomes 1 and 7, t(1;7)(q42;p15), the breakpoints of which could represent a WT predisposition gene in this patient. Cytogenetic analysis of the tumor from this patient revealed an acquired abnormality of the other chromosome 7, resulting in an isochromosome of the long arm and a 46,XY,t(1;7)(q42;p15)c,i(7)(q10) karyotype. The regions of the translocation breakpoints were investigated in a series of 24 WTs using Southern blot analysis. This confirmed the monosomy of 7p and trisomy of 7q in the tumor of the translocation patient, and in addition a loss of chromosome 7p alleles was identified in a WT of a bilaterally affected patient. In addition, two WTs were shown to have an extra copy of chromosome 7 alleles. Multiple copies of chromosome 1q alleles, probably resulting from secondary changes, were observed in two WTs, one of which was also associated with a trisomy of chromosome 7. These results indicate that 7p may contain a tumor suppressor gene involved in WT development, and that duplications of 7q also may play a role in WT development.