Induction of early apoptosis in human nasopharyngeal carcinoma cells by mTHPC-mediated photocytotoxicity

Objectives: In this study, the early apoptotic events elicited by mTHPC-mediated photocytotoxicity were explored in a human nasopharyngeal carcinoma cell, line (NPC/HK1). Methods and materials: NPC/HK1 cells (5 x 10(3)) were incubated with photosensitizer mTHPC (0.8 mu g/ml) in chamber slides for 20 h and subjected to tight irradiation at 2J/cm(2) (LD80). Morphologic changes of treated cells were examined under light microscopy and confocal microscopy at 0-4 h after the light irradiation. The early stage of apoptosis was I detected by fluorescein-conjugated Annexin V (Annexin V-FITC) assay. Mitochondrial. membrane damage and cytochrome c release were determined by flowcytometric analysis. Bcl-2 expression was measured by Western blot analysis. Results: One hour after mTHPC-mediated photodynamic therapy (PDT), microscopic nation showed membrane blebbing and cell shrinkage. Annexin V-FITC assay showed that considerable number of NPC/HK1 cells became apoptotic. Flowcytometric analysis showed that the cytochrome c was released at I h after PDT. Bcl-2 expression also declined significantly compared to control groups. Conclusions: mTHPC-mediated photo-cytotoxicity can effectively induce early apoptotic responses in NPC/HK1 cells which might be modulated by mitochondrial damages and Bcl-2 inhibition. (C) 2009 Etsevier B.V. All rights reserved.