Experimental evidence on possibility to radiosensitize aggressive tumors by porphyrins

Two murine experimental tumor models of different aggressiveness (murine Ehrlich ascitic carcinoma and MH-22A hepatoma) were used to investigate the radiosensitization by porphyrins. Data obtained clearly indicate that hematoporphyrin dimethyl ether, photofrin and hematoporphyrin derivative exert some radiosensitizing properties which are in clear correlation with purity of the compound. Of interest to note, that just aggressive Ehrlich ascitic carcinoma was radiosensitized to gamma-radiation, whereas no signs of radiosensitization were observed in MH-22A hepatoma tumor. Data obtained support the idea, that dicarboxylic porphyrins, being ligands of peripheral benzodiazepine receptors (responsible for proliferation and highly expressed in aggressive tumors) might induce several sublethal injuries in the cell which further work in concert with ionizing radiation producing synergistic interaction of two antiproliferative factors.