Estramustine reversal of resistance to intravesical epirubicin chemotherapy

Objective: Failure of epirubicin treatment of superficial bladder cancer im plies multidrug resistance (MDR) which is common. MDR is characterised by d ecreased cellular levels of drug. TCC cell lines sensitive to epirubicin an d resistant to both epirubicin and mitomycin C were used to investigate aug mented therapy by adding the MDR reversing agent estramustine to an in vitr o model. Methods: Cells were cultured as monolayers. Fluorescence analysis was performed by flow cytometry and confocal microscopy. Cells were exposed to epirubicin 20 mu g/ml for 2 h and increasing amounts of estramustine. C ytotoxicity was determined under similar exposure conditions and MTT cultur e (dye reduction by live cells) allowed viable biomass to be read optically . Results: Resistant cells accumulated eight times less epirubicin than sen sitive cells. Confocal microscopy confirmed this for nuclear uptake. Accumu lation in resistant cells can be increased to near-sensitive cell levels us ing 40 mu g/ml estramustine. Image analysis of confocal fluorescence showed a shift from cytoplasm to nucleus. This correlated with increased cytotoxi city. Conclusion: Estramustine plus epirubicin chemotherapy can overcome MD R and may achieve more successful tumour killing in vivo. It may also preve nt emergence of resistance. Primary TCC culture examination permits detecti on of sensitive and resistant cells and may predict outcome allowing a more logical treatment selection.