Decreased expression of the Id3 gene at 1p36.1 in ovarian adenocarcinomas

The molecular events that drive the initiation and progression of ovarian a denocarcinoma are not well defined. We have investigated changes in gene ex pression in ovarian cancer cell lines compared to an immortalized human ova rian surface epithelial cell line (HOSE) using a cDNA array. We identified 17 genes that were under-expressed and 10 genes that were over-expressed in the cell lines compared to the HOSE cells. One of the genes under-expresse d in the ovarian cancer cell lines, Id3, a transcriptional inactivator, was selected for further investigation. Id3 mRNA was expressed at reduced leve ls in 6 out of 9 ovarian cancer cell lines compared to the HOSE cells while at the protein level, all 7 ovarian cancer cell lines examined expressed t he Id3 protein at greatly reduced levels. Expression of Id3 mRNA was also e xamined in primary ovarian tumours and was found in only 12/38 (32%) cases. A search was conducted far mutations of Id3 in primary ovarian cancers usi ng single stranded conformation polymorphism (SSCP) analysis. Only one nucl eotide substitution, present also in the corresponding constitutional DNA, was found in 94 ovarian tumours. Furthermore no association was found betwe en LOH at 1p36 and lack of expression of Id3. These data suggest that Id3 i s not the target of LOH at 1p36. (C) 2001 Cancer Research Campaign.