EFFECT OF PHOTODYNAMIC THERAPY IN COMBINATION WITH MITOMYCIN-C ON A MITOMYCIN-RESISTANT BLADDER-CANCER CELL-LINE

Photodynamic therapy is a method for treating cancer using drugs activ ated by light. A new compound, 5-aminolaevulinic acid (ALA), is a prec ursor of the active photosensitizer protoporphyrin IX (PpIX) and has f ewer side-effects and much more transient phototoxicity than previous photosensitizers. Cell survival of ALA-mediated photodynamic therapy w as measured in the J82 bladder cancer cell line, along with its mitomy cin C-resistant counterpart J82/MMC. This demonstrated that mitomycin resistance is not cross-resistant to photodynamic therapy. There was a lso a suggestion that the mitomycin-resistant cells were more suscepti ble to photodynamic therapy than the parent cell line. Photodynamic th erapy appeared to enhance the effect of mitomycin C, when mitomycin C was given first. This phenomenon was apparent for both drug-resistant and drug-sensitive cell lines. This suggests a possible role for combi ned mitomycin C and photodynamic therapy in superficial bladder tumour s that have recurred despite intravesical cytotoxic drug treatment.