Collateral susceptibility of adriamycin-, melphalan- and cisplatin-resistant human ovarian tumor cells to bleomycin.

Three cell lines resistant to adriamycin, melphalan and cisplatin were established in vitro from human ovarian cancer cell line A2780. Each subline showed a resistance to its inducing drug of 75-fold in the case of adriamycin, 6-fold in the case of melphalan and 11-fold in the case of cisplatin. However, all of these sublines showed collateral sensitivity to bleomycin. Approximately a 2-fold higher susceptibility to bleomycin was observed generally. The biochemical mechanisms of this collateral sensitivity are not clear at present, but the higher concentration of glutathione in these resistant tumor cell lines might be related to the high susceptibility of these resistant cells to bleomycin.