The Phototoxic Effect of Water-Soluble Porphyrins on Human Clear Cell Renal Cell Carcinoma Line Сaki-1

Two tetrapyridine porphyrins, cationic porphyrin P4 (TMPyP4) and its amphiphilic derivative porphyrin P1 with carboxyl groups, and their zinc-containing analogs ZnP4 and ZnP1 were examined in order to obtain the photosensitizers with a narrower specificity for target tissue. The two classes of molecules were compared with respect to physicochemical properties of and the effect on Caki-1 clear cell renal cell carcinoma cells in vitro. Micromolar concentrations of the compounds did not cause morphological changes in cells in the absence of light irradiation. Cell treatment with porphyrin porphyrin P4 under blue light led to a rapid cytotoxic effect. The cells began to detach from the substrate, and swellings (blebs) became detectable in their membranes. The rate of the changes was consistent with direct membrane damage by porphyrin P4. Compound ZnP1 did not cause any visible changes in Caki-1 cell morphology in similar conditions. The results were explained by different lipophilicities and, therefore, different intracellular localization of the compounds. Membrane localization was assumed to prevail in the case of porphyrin P4, which is more lipophilic then ZnP1, and to mediate its fast cytopathic effect.