Selection of human ovarian carcinoma cells with high dissemination potential by repeated passage of the cells in vivo into nude mice, and involvementof Le(x)-determinant in the dissemination potential

Cells of the human tumor cell line RMG-1, derived from a clear-cell adenoca rcinoma of the ovary, were injected intraperitoneally into nude mice, and t he cells obtained from the tumor nodules in the mesenterium were found to f orm a larger number of, and larger-sized, tumor nodules than the original R MG-1 cells, The RMG-1-h cells, transferred into culture from the tumor nodu les after a 4th in vivo passage, showed a dissemination potential as high a s that of cells disseminating directly from the tissues, and exceedingly hi gher than that of RMG-1 cells. To assess the molecular bases of the differe nt biological properties of RMG-1 and RMG-1-h cells, we compared the conten t and expression of various carbohydrate antigens in both cells. The chromo somal profile of RMG-1-h cells revealed their human origin and was identica l to that of the original R1LYG-1 cells. In contrast to the broad histogram for the Le(x)-bearing cells among RMG-1 cells in flow cytometry, the weakl y and moderately positive cells toward anti-Le(x) antibody were found to be eliminated from the histogram for the RMG-1-h cells, resulting in the enri chment of cells strongly expressing Le(x), which may account for the high d issemination potential. In addition, the adhesion of RMG-1 cells to mesothe lial cells was found to be significantly inhibited by pretreatment of the c ells with anti-Le(x) antibody, indicating Le(x)-mediated cell-to-cell inter action between ovarian cancer cells and mesothelial cells. By TLC-immunosta ining, two Le(x)-glycolipids, III(3)Fuc alpha-nLc(4)Cer and V(3)Fuc alpha-n Lc(6)Cer were detected in both RMG-1 and RMG-1-h cells, and their total con centrations were not significantly different from each other. However, the hydrophobic moieties of Le(x)-glycolipids in RMG-1-h cells were different f rom those in RMG-1 cells, suggesting that a difference in the structure of the hydrophobic moieties of Le(x) is partly involved in the enhanced reacti vity of RMG-1-h cells toward anti-Le(x) antibody. Thus, the high disseminat ion potential of ovarian cancer cells was shown to be mediated by the Le(x) -determinant and the Le(x)-bearing cells are enriched by repeated in vivo p assage of the cells into nude mice.