Intravesical chemotherapy for superficial bladder cancer : an in vitro study of anthracyclines, pH and multidrug resistance

Trials have demonstrated a reduction in bladder cancer recurrence rates of approximately 45% following intravescial chemotherapy. Treatment failures are likely to be due, at least in part, to the development of clones of tumour cells expressing resistance to these chemotherapy agents. This study has addressed the methods available for increasing the efficacy and response rates of epirubicin and doxorubicin-based chemotherapy.An anthracycline-sensitive bladder cancer cell line together with a multidrug resistant subline has been used in this in vitro study. Utilising the inherent fluorescence of the anthracyclines, we have quantified their rate of uptake over time, the effect of multidrug resistance reversing agents and the effect of pH changes in equivalent drug sensitive and drug resistant bladder cancer cells using flow cytometry. The intracellular distribution of these agents has been studied under similar conditions using confocal microscopy and the relevance of these findings to proposed mechanisms of MDR is discussed. Spectrofluorimetry has been used to establish the behaviour of these agents both in free solution and bound to DNA at a variety of pH levels. The conclusions have been tested using the MTT cytotoxicity assay.In the bladder cancer cell line expressing the MDR phenotype, a significant increase in drug uptake and cytotoxicity can be demonstrated by the addition MDR reversing agents.Alkalinisation of the anthracycline solution also independently increases drug uptake and cytotoxicity in sensitive cells as well as in resistant cells treated with MDR reversing agents, independently of the direct cytotoxicity of the alkaline medium. These affects appear to be additive.