Photosensitizing action of phthalocyanine for photodynamic therapy

In photodynamic therapy, a photosensitizer is administered to a cancer patient, and the tumor is necrosed by irradiation with laser beams. The current photosensitizer porphyrin has defects such that tumor selectivity is low, and that the absorption coefficient of light in the long wavelength region having good tissue permeability is small. The authors have developed a novel water-soluble fluorinated phthalocyanine having absorption in the long wavelength region. They have also developed antitumor antibody-binding type zinc phthalocyanine. This paper explained the experiments on the uptake of water-soluble fluorinated phthalocyanine into HeLa cells and on the phototoxicity, as well as the experiments to measure the accumulation amount of antitumor antibody-binding type zinc phthalocyanine in MM46 cells and the accumulation amount in each organ in tumor-bearing mice. This paper showed an example of photodynamic therapy for the solid tumor of mice using water-soluble fluorinated phthalocyanine. In the solid tumor 5 days after treatment, high antitumor effect was found. Antitumor antibody-binding type zinc phthalocyanine showed higher intracellular accumulation and cytocidal effects than the case without binding to antibody. Moreover, it was found that the amount of accumulation of this chemical in the muscles and skin, where light hypersensitivity is likely to occur, is much lower. (A.O.)