Abstract

Background:Nasopharyngeal carcinoma (NPC) is one of the most common cancers, and exploring novel therapeutic modalities will improve the clinical outcomes. It has been confirmed that photodynamic therapy can efficiently deactivate malignant cells. The aim of the present study was to explore the photodynamic effects of pyropheophorbide-a methyl ester (MPPa) in CNE2 nasopharyngeal carcinoma cells.

Material/Methods: CNE2 cells were subjected to photodynamic therapy with MPPa, in which the drug concentration was 0.25 to 4 µM and light energy 1 to 8 J/cm[sup]2[/sup]. Photodynamic toxicity was investigated 24 h after treatment. Apoptosis was determined using flow cytometry with annexin V-FITC and propidum iodine staining and with nuclear staining with Hoechst 33258. The mitochondrial membrane potential (ΔΨm) was evaluated by Rhodamine 123 assay.

Results: There was no dark cytotoxicity of MPPa in the CNE2 cells at doses of 0.25–4 µM, and MPPa resulted in dose- and light-dependent phototoxicity. The apoptotic rate 8 h after PDT with MPPa (2 µM) increased to 16.43% under a light energy of 2 J/cm[sup]2[/sup]. Mitochondrial membrane potential (ΔΨm) collapsed when the CNE2 cells were exposed to 2 µM MPPa for 20 h and then 2 J/cm[sup]2[/sup] irradiation.

Conclusions:Photodynamic therapy with MPPa significantly enhanced apoptosis and the collapse of ΔΨm. This can be developed for treating nasopharyngeal carcinoma.

Keywords: Cell Death - drug effects, Membrane Potentials - drug effects, Mitochondrial Membranes - drug effects, Nasopharyngeal Neoplasms - drug therapy, Photochemotherapy - methods, Photosensitizing Agents - therapeutic use, Porphyrins - therapeutic use, Tumor Cells, Cultured