title: Induction of early apoptosis in human nasopharyngeal carcinoma cells by mTHPC-mediated photocytotoxicity.
abstract: OBJECTIVE
  In this study, the early apoptotic events elicited by mTHPC-mediated photo-cytotoxicity were explored in a human nasopharyngeal carcinoma cell line (NPC/HK1).
  
  
  METHODS
  NPC/HK1 cells (5 x 10(3)) were incubated with photosensitizer mTHPC (0.8 microg/ml) in chamber slides for 20h and subjected to light irradiation at 2J/cm(2) (LD(80)). Morphologic changes of treated cells were examined under light microscopy and confocal microscopy at 0-4h after the light irradiation. 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. Bcl-2 expression was measured by Western blot analysis.
  
  
  RESULTS
  One hour after mTHPC-mediated photodynamic therapy (PDT), microscopic examination showed membrane blebbing and cell shrinkage. Annexin V-FITC assay showed that a considerable number of NPC/HK1 cells became apoptotic. Flowcytometric analysis showed that the cytochrome c was released at 1h 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.
authors.affiliation: Department of Health Technology Informatics, Medical Laboratory Science, Hong Kong Polytechnic University, Hong Kong SAR, China. htcyow@inet.polyu.edu.hk
authors.forename: Christine M N
authors.initials: CM
authors.lastname: Yow
authors.forename: N K
authors.initials: NK
authors.lastname: Mak
authors.forename: Albert W N
authors.initials: AW
authors.lastname: Leung
authors.forename: Zheng
authors.initials: Z
authors.lastname: Huang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D006801:Humans; D008652:Mesoporphyrins / Q000494:pharmacology*; D009303:Nasopharyngeal Neoplasms / Q000628:therapy*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*
chemical_list: D008652:Mesoporphyrins; D017319:Photosensitizing Agents; C072269:temoporfin