Loss of heterozygosity in Wilms' tumour involves two distinct regions of chromosome 11.

Pairs of tumour and normal DNA samples from 38 Wilms' tumour patients have been investigated for loss of heterozygosity using 12 probes from chromosome 11. Allele loss was detected in only 11 cases (31%). Densitometric analysis showed that allele loss was not due to non-disjunction or hemizygous deletion, but rather to mitotic recombination or non-disjunction plus reduplication. Although the development of homozygosity sometimes involved the whole of the short arm of chromosome 11, in a few tumours allele loss was restricted to band 11p15 or 11p13 and distal sequences. This suggests mutations in two distinct regions play an important role in Wilms' tumorigenesis. There was no apparent correlation between loss of heterozygosity and tumour stage, age of presentation, or prior exposure to chemotherapy.