Photokilling of cultured tumour cells by the porphyrin derivative CF3.

We have analysed the photosensitizing properties of the new porphyrin 5-(4-N-(N-2',6'-dinitro-4'-trifluoromethylphenyl)aminophenyl)-10,15,20-tris(2,4,6-trimethoxyphenyl) porphyrin (CF3) on HeLa cells. The fluorescence and singlet oxygen quantum yield for CF3 were, respectively, phiF = 0.032 and phidelta = 0.25. Cell treatments were done with 5 x 10(-6) M CF3 incorporated into liposome vesicles. Under violet-blue exciting light, the red fluorescence of CF3 was mainly detected in lysosome-like granules. No dark cytotoxicity was observed using high concentration (5 x 10(-6) M) and long incubation time (18 h). Cell cultures treated for 18 h with CF3 and exposed to light (360 < lambda < 460 nm; 8 mW/cm2) for 7 min revealed a great amount of apoptotic (75.8%) and detached cells (62%) 8 h later, leading to a cell lethality of 85% (LD85). Apoptosis was identified by chromatin fragmentation and DNA ladder in gel electrophoresis. Necrotic cells were found using 15 min irradiation (LD96) and showed first small and then giant bubbles at the cell surface, with homogeneous nuclear condensation. Incubation with CF3 for 3 h followed by 7 min irradiation (LD38) produced a mitotic arrest 18 h later (mitotic index: 25.1%). Forty-eight hours after this metaphase blockage, cultures showed a great number of apoptotic cells. Taking into account these results, CF3 could be a valuable photosensitizer for the photodynamic therapy of cancer.