Abstract: Objective　To investigate the photosensitization of photodynamic therapy (PDT) mediated by zinc phthalocyanines tetrasubstituted with carboxyl moieties on oral squamous cell carcinoma (OSCC) cells in vitro. Methods The human OSCC cell line HN4 was studied. The experiments were divided into dark reaction group and light reaction group and the cells in the light reaction group received vertical irradiation with gradient light dose. The effect of different light doses on cell proliferation was detected by Cell Counting kit-8 (CCK-8). The effects on cell cycle changes and apoptosis were determined with flow cytometry. The changes of Caspase-3, Bcl-2 expression were examined before and after the interference by Western-blot. Results Both drug concentration and light dose affected cell proliferation (P<0.05). The 50% inhibition concentration (IC50) in the dark reaction group was significantly higher than that in the light reaction groups (P<0.05). Within the certain concentration range, with the improvement of drug concentration, the S phase of the cell cycle relatively decreased, the G2/M phase relatively increased, the number of cell apoptosis increased, the Caspase-3 expression increased while the Bcl-2 expression decreased (P<0.05). Conclusion Zinc phthalocyanines tetrasubstituted with carboxyl moieties is an effective anti-cancer drug, which can effectively induce the apoptosis of OSCC.

Key words: photodynamic therapy, zinc phthalocyanine, oral squamous cell carcinoma cells, cell apoptosis.