EFFECT OF PHOTODYNAMIC ACTION WITH PHEOPHORBIDE-A ON HUMAN ORAL CARCINOMA CELLS IN SERUM-FREE CULTURE

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We have examined effects of photodynamic action with pheophorbide-a (Ph-a) on the growth of various types of cultured carcinoma cells in serum-free culture. It has been revealed that squamous cell carcinoma cells (SCC) exhibited high sensitivity to Ph-a in comparison with salivary gland-derived adenocarcinoma cells (SAC). The SCC demonstrated an increased intracellular level of Ph-a compare to that of SAC. In addition, we have investigated lipid composition of cell-membrane of both cells under serum-free culture. It became evident that 60% of membrane lipids of SCC was phospholipids (PL) and 80% of those of SAC was neutral lipids (NL). The NL/PL ratio indicated that SCC showed low levels but SAC showed remarkably high levels. These result indicated that the cytotoxity of PDT correlated with the intracellular levels of Ph-a resulted from the difference of membrane hydrophobicity. In addition, it became clear that SAC exhibited an increased level of both reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) activity in comparison to those of SCC. The SCC which showed decreased sensitivity to Ph-a, exhibited a extrimely high level of glutathione S-transferase (GST)activity. Consequently, GSH, GSH-Px and GST function another factors determining photosensitivity of the cells. These findings suggested that photodynamic therapy might be a useful treatment for squamous cell carcinomas.