title: Thymoquinone induces cell death in human squamous carcinoma cells via caspase activation-dependent apoptosis and LC3-II activation-dependent autophagy.
abstract: BACKGROUND
  Thymoquinone (TQ), an active component of Nigella sativa or black cumin, elicits cytotoxic effects on various cancer cell lines. However, the anti-cancer effects of TQ on head and neck squamous cell carcinoma (HNSCC) remain unclear.
  
  
  RESULTS
  In this study, TQ elicited a strong cytotoxic effect on SASVO3, a highly malignant HNSCC cell line. The mechanisms of this cytotoxic effect were concentration dependent. TQ also induced apoptotic cell death in SASVO3 cells as indicated by an increase in Bax expression and caspase-9 activation. Apoptosis was possibly caspase-9 dependent because the exposure of cells to a caspase-9 inhibitor partially prevented cell death. The exposed cells also showed increased levels of autophagic vacuoles and LC3-II proteins, which are specific autophagy markers. Cell viability assay results further revealed that bafilomycin-A1, an autophagy inhibitor, enhanced TQ cytotoxicity; by comparison, Annexin V and propidium-iodide staining assay results showed that this inhibitor did not promote apoptosis. TQ treatment also increased the accumulation of autophagosomes. Using a lentivirus-shRNA system for LC3 silencing, we found that cell viability was eradicated in autophagy-defective cells. An in vivo BALB/c nude mouse xenograft model further showed that TQ administered by oral gavage reduced tumor growth via induced autophagy and apoptosis.
  
  
  CONCLUSIONS
  These findings indicated that TQ induced cell death in oral cancer cells via two distinct anti-neoplastic activities that can induce apoptosis and autophagy. Therefore, TQ is a promising candidate in phytochemical-based, mechanistic, and pathway-targeted cancer prevention strategies.
authors.affiliation: Institute and Department of Food Science, Central Taiwan University of Science and Technology, Taichung, Taiwan.
authors.forename: Shu-Chen
authors.initials: SC
authors.lastname: Chu
authors.affiliation: Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung, Taiwan; Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan.
authors.forename: Yih-Shou
authors.initials: YS
authors.lastname: Hsieh
authors.affiliation: Institute of Oral Science, School of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan; Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan.
authors.forename: Cheng-Chia
authors.initials: CC
authors.lastname: Yu
authors.affiliation: Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Yi-Yeh
authors.initials: YY
authors.lastname: Lai
authors.affiliation: Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung, Taiwan; Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan.
authors.forename: Pei-Ni
authors.initials: PN
authors.lastname: Chen
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D016227:Benzoquinones / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D018942:Macrolides / Q000494:pharmacology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D010588:Phagosomes / Q000187:drug effects; D000077195:Squamous Cell Carcinoma of Head and Neck; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; C477012:MAP1LC3A protein, human; D018942:Macrolides; D008869:Microtubule-Associated Proteins; C040929:bafilomycin A1; D020169:Caspases; C003466:thymoquinone