EVALUATION OF THE PROBABILITY OF SPONTANEOUS TRANSFER OF DRUG-RESISTANCE BETWEEN CELLS IN CULTURE

Coculture of two different cell lines in monolayer or spheroids was used to investigate the spontaneous transfer of dominant genes determining drug resistance. MGH-U1 human bladder cancer cells (ouabain-sensitive, mitomycin C-resistant) were cocultured with UV-20 cells (a subline of Chinese hamster ovary cells which is ouabain-resistant and mitomycin C-sensitive). We investigated the possible transfer of mitomycin-C resistance from human to rodent cells by selection in both ouabain and mitomycin C. Regardless of coculture conditions, the frequency of surviving cells was at a similar level to that expected from studies of cell survival when cells were cultured alone. We found no evidence of spontaneous transfer of drug resistance between the two cell lines.