LOSS OF HETEROZYGOSITY AT 11P13 IN WILMS-TUMORS DOES NOT NECESSARILY INVOLVE MUTATIONS IN THE WT1 GENE

Loss of heterozygosity (LOH) in tumour cells is generally accepted as 'exposing' recessive cancer genes. The short arm of chromosome 11 shows consistent LOH in Wilms' tumours along its entire length. Occasionally, however, only the 11p13 and/or the 11p15 regions are involved. Deletions of the 11p13 region consistently predisposes to Wilms' tumorigenesis. We have analysed the recently cloned WT1 gene from the 11p13 region exon-by-exon in five tumours previously shown to have undergone LOH for the 11p13 region, using single strand conformation polymorphism analysis (SSCP) and PCR sequencing. Our analysis using SSCP failed to identify any band shifts in the WT1 gene from these tumours. In addition we also sequenced the zinc finger region of WT1, which is the part of the gene most frequently showing mutations. Only the normal sequence was found in all of these tumours. These results demonstrate that LOH in Wilms' tumours is not always related to mutations in the WT1 genes and argues strongly that another gene, probably in the 11p15 region, may be more important in Wilms' tumorigenesis.