Characterization and tumorigenicity of human ovarian surface epithelial cells immortalized by SV40 large T antigen

Objectives. Epithelial ovarian cancers are considered to arise from neoplas tic transformation of the ovarian surface epithelium (OSE). However, the ea rliest events in ovarian carcinogenesis have not been clearly defined becau se patients are often diagnosed in the advanced stages and useful in vivo a nd in vitro experimental systems using human OSE cells are lacking. We aime d to improve the availability of experimental models for the study of human ovarian carcinogenesis. Methods. Subcultured human OSE cells were transfected with SV40 large T ant igen. Resulting OSE cell lines were characterized using immunocytochemistry and tested tumorigenicity. Results. Six immortalized OSE cell lines were obtained. All cell lines esse ntially retained the original morphological features of normal OSE cells an d showed higher proliferation rates and saturation density. Although they w ere all nontumorigenic in athymic mice, OSE2b-2 sv cells, which were select ed in soft agar from colonies of an SV40 large T antigen-expressing transfe ctant, OSE2b sv, produced tumors on the peritoneal surface, mesothelium, an d diaphragm and induced ascites after being injected intraperitoneally. Sol id tumors also grew when mice were inoculated subcutaneously. The tumor cel ls were formed in a solid sheet arrangement and no evidence of glandular or squamous differentiation was present. They were weakly immunostained with an antibody against cytokeratin, and intercellular junctions resembling att achment devices were ultrastructurally present between cells. The tumors we re histologically diagnosed as undifferentiated carcinomas. Conclusions. The established cell lines may provide a model system to inves tigate the mechanisms of cytogenic and molecular changes from normal OSE ce lls through the various steps of transformation. (C) 2001 Academic Press.