Cellular binding of hematoporphyrin derivative (HpD) in human bladder cancer cell line: KK-47

In vitro cellular uptake or binding of hematoporphyrin derivative (HpD) was investigated by comparing the optical properties; absorption spectra, fluorescence spectra, fluorescence lifetime and fluorescence polarization, of HpD in KK-47 cells derived from a human bladder carcinoma, organic and micellar solutions. In addition, the relationship between the mode of cellular HpD uptake and photodynamic cellular inactivation by argon-dye laser was studied using a clonogenic assay system. HpD molecules may weakly bind to the cell membrane within approximately 2 hrs after incubation in HpD-containing medium, and then major HpD molecules may slowly be distributed throughout the cytoplasm as a dimer form for 4 hrs after incubation in HpD-free medium. The intracellular binding loci were found to be the mitochondria and nuclear membrane by subcellular fractionation and fluorescence microscopic studies. The loci may be relatively hydrophilic on the basis of the polarity-dependence data on the fluorescence polarization. An exponential cellular photoinactivation curve was observed in relation to increasing concentrations of HpD and to intracellular strong-binding of dimeric HpD.