[Role of PpIX-based photodynamic therapy in promoting the damage and apoptosis of colorectal cancer cell and its mechanisms].

OBJECTIVE:To explore the effects of protoporphyrin IX (PpIX)-mediated photodynamic therapy (PDT) on induction of apoptosis and death in colon cancer cell and the underlying mechanisms.
 Methods: The cell killing effect of PDT on HCT116 cell was determined by cell counting kit (CCK). The cells were divided into a control group, a single light group, a single PpIX group, and a PDT group. Hoechst 33342 and flow cytometry was used to assess the cell apoptosis. Western blot was employed to analyze the expressions of bcl-2, bax, and caspase-3. Reactive oxygen species (ROS) was detected by flow cytometry.
 Results: The viability of HCT116 cell was decreased gradually with the increase of irradiation dose (P<0.05). Compared to the other 3 groups, ROS production, the number of apoptotic cells and the protein expressions of bax and caspase-3 in PDT group increased, while bcl-2 expression was decreased (P<0.05).
 Conclusion: PpIX-mediated PDT can enhance the apoptosis in HCT116 cell, which may be related to mitochondrial apoptosis pathway.