mTHPC-photodynamic therapy induced apoptosis in nasopharyngeal carcinoma cells

In this study, the early apoptotic events of mTHPC-medicated photodynamic therapy (PDT) was explored in two human nasopharyngeal carcinoma (NPC) cell lines - NPC/HK1 cells and NPC/CNE2 cells. Cells (5 X 10(3)) were incubated with mTHPC (0.8 mu g/ml) in chamber slides for 20 h and subjected to light irradiation at 2 J/cm(2) (LD80)- Morphologic changes of treated cells were examined at 0- 4 h after the light irradiation by a light microscopy. The early stage of apoptosis was detected by fluorescein-conjugated Annexin V (Annexin V-FITC) assay. Mitochondrial membrane damage and cytochrome c release were determined by flowcytometric analysis. The Bcl-2 expression was measured by Western blot analysis. One hour after mTHPC-mediated PDT, membrane blebbing and cell shrinkage appeared in both HK1 and CNE2 cells. Annexin V-FITC assay showed that a considerable number of HK 1 and CNE2 cells became apoptotic at 1 h after PDT. Flowcytometric analysis showed that the cytochrome c was released at 1 h after PDT. The Bcl-2 expression also declined significantly in both cell lines compared to the control groups. mTHPC-mediated PDT can effectively induce apoptotic responses in NPC cells which might be modulated by mitochondrial damage and Bcl-2 inhibition.