Frequent loss of heterozygosity at 1p36 in ovarian adenocarcinomas but thegene encoding p73 is unlikely to be the target

Loss of heterozygosity (LOH) involving the distal part of the short arm of chromosome 1 occurs frequently in ovarian adenocarcinomas but the tumour su ppressor gene(s) targeted by this event is unknown, We have used five micro satellite markers in a panel of 56 ovarian adenocarcinomas to determine whi ch part of 1p34-36 is the focus of this LOH, LOH was considerably more comm on at 1p36 (43%) than at 1p34-35 (18%), and 11 tumours showed LOH at 1p36 b ut not at 1p34-35, These data strongly suggest the presence of a tumour sup pressor gene inactivated in ovarian adenocarcinoma at 1p36, The p53 homolog ue, p73, has recently been isolated and mapped to 1p36 and therefore is a c andidate for this tumour suppressor gene, However, RT-PCR and Western analy ses revealed strong expression of p73 in ovarian adenocarcinoma cell lines but very low or undetectable levels in normal ovarian surface epithelial ce lls. Immunohistochemical analysis of primary ovarian tumours showed that on ly 3/22 (14%) contained p73 expressing cells. There was no association betw een 1p36 LOH and p73 expression in ovarian tumours, nor between p73 and p53 expression, These findings strongly suggest that p73 is not the target of 1p36 LOH in ovarian adenocarcinomas but indicate the presence of an, as yet unidentified, tumour suppressor gene in this region that plays an importan t role in ovarian tumorigenesis.