Photodynamic effects of 5-aminolevulinic acid-induced porphyrin on human bladder carcinoma cells in vitro

Abstract The efficiency of 5-aminolevulinic acid (ALA) in photodynamic therapy (PDT) was investigated in vitro using urothelial carcinoma cells of various differentiation. HCV29, RT4 and J82 cells were cultured in 96-well plates, incubated with 25–100 μg/ml ALA in serum-containing medium for 4 h, and irradiated at 630, 635 and 640 nm wavelength with light doses of 15–100 J/cm 2 . The degree of reduced tetrazolium bromide corresponding to cell viability was determined with a colorimetric MTT assay 0, 24 and 48 h after PDT. A remarkable reduction of mitochondrial activity occurred in poorly (J82) and well differentiated (RT4) malignant urothelial cells. Twenty-four hours after photodynamic treatment with 100 μg/ml ALA and 50 J/cm 2 , the metabolic activity of malignant cells was nearly extinguished, while HCV29 cells, derived from normal urothelium, behaved similarly to non-irradiated control cells. The photosensitivity of cells depended on presence or absence of fetal bovine serum (FBS) in the ALA-incubation medium. A wavelength of 635 nm was up to 60% more effective compared with 630 nm, which is more frequently applied in PDT. From the results of our in vitro studies, we can define a “therapeutic window” for malignant cells without damaging benign cells. The tune delayed effects and the strong wavelength dependence are important factors for a clinical application.