Multi-drug resistance of a doxorubicin-resistant bladder cancer cell line.

A bladder tumor cell line resistant to doxorubicin (MGH-U1R) has been established previously by culturing a human transitional cell carcinoma cell line (MGH-U1) in increasing concentrations of the drug. MGH-U1R is 40 times more resistant to doxorubicin than MGH-U1. In the present study, MGH-U1R was evaluated for its multi-drug resistance or pleiotropism by testing against other chemotherapeutic agents. MGH-U1R was found to be 188 times more resistant to vinblastine and 13 times more resistant to etoposide than MGH-U1, while remained sensitive to bleomycin. Taken together with earlier evidence that the resistance of MGH-U1R to doxorubicin can be reversed by a calcium-channel blocker verapamil, and the measured over-expression of the mdr1 gene in these cells, MGH-U1R has the characteristic multiple drug resistance properties similar to other established doxorubicin resistant carcinoma cell lines. MGH-U1R may be a useful model for the development of strategies in overcoming drug-resistance in the treatment of transitional cell carcinoma.