Effects of chlorin e6-mediated photodynamic therapy on human colon cancer SW480 cells

Objective: This study is to investigate the antitumor effects and possible mechanisms of chlorin e6-mediated photodynamic therapy (Ce6-PDT) on human colon cancer SW480 cells. Methods: SW480 cells were treated with Ce6, followed by photodynamic irradiation. Subcellular localization of Ce6 in SW480 cells was observed with confocal laser scanning microscopy (LSCM). Reactive oxygen species (ROS) levels were monitored with fluorescence microscopy. Cell proliferation and apoptosis were detected by the MTT assay and flow cytometry, respectively. Scratch test and colony formation assay were employed to analyze the cell migration ability and colony formation ability. Results: LSCM showed that, in SW480 cells, Ce6 was evenly distributed within the ER and lysosomes, with nearly no distribution in the mitochondria and nuclei. When SW480 cells were subjected to Ce6-PDT, the ROS levels would be elevated, in a dose-dependent manner. Moreover, Ce6-PDT treatment could inhibit the cell proliferation and enhance the apoptotic process, in SW480 cells. However, Ce6 treatment alone without photodynamic irradiation could not induce any significant differences in the cell proliferation and apoptosis. In addition, the migration ability and colony formation ability of SW480 cells were decreased by Ce6-PDT treatment at appropriate dosages. Conclusion: Ce6-PDT treatment could enhance ROS production and apoptosis, inhibit cell proliferation, decrease migration ability and colony formation ability, in SW480 cells, in a dose-dependent manner. These findings might provide experimental evidence for the application of Ce6-PDT in clinical treatment of colorectal cancer.