Identification of clinically relevant genes on chromosome 11 in a functional model of ovarian cancer tumor suppression.

Microcell-mediated transfer of normal chromosome 11 (chr 11) to a clonal derivative of the ovarian cancer cell line, OVCAR3, was performed and generated independent hybrids with a common set of phenotypes: inhibition of cell growth and of cellular migration in vitro; and inhibition of tumor growth in vivo. Differential display reverse transcriptase-PCR (RT-PCR), cDNA-representational difference analysis, and hybridization of cDNA high-density filter arrays identified altered mRNAs associated with these phenotypic alterations. Quantitative RT-PCR-based validation of each altered mRNA eliminated false positives to identify a reduced set of expression differences. Twelve products were confirmed as up-regulated and 4 as down-regulated upon introduction of chr 11. Strikingly, 4 of the 12 up-regulated genes were located on chr 11. Expression analysis of selected products by quantitative RT-PCR in a series of 18 human primary ovarian tumors revealed several associations with clinicopathological features. Importantly, low expression of two products, the lysosomal protease CTSD and the lens crystallin CRYAB, was significantly associated with adverse patient survival. Immunohistochemical analysis of CTSD in a larger independent panel of 58 primary ovarian tumors confirmed that low CTSD was associated with poor survival. Furthermore, low CTSD was significantly associated with serous histology and advanced tumor stage. The combined approach of microcell-mediated chromosome transfer and expression difference analysis has identified several altered mRNAs in a model of chr 11-mediated ovarian tumor suppression. The detailed contextual characterization of these genes will determine the extent of their involvement in neoplastic development.