title: Autophagy and reactive oxygen species modulate cytotoxicity induced by suppression of ATM kinase activity in head and neck cancer cells.
abstract: OBJECTIVE
  Because Ataxia Telangiectasia Mutated (ATM)-deficient cells are hypersensitive to ionizing irradiation and DNA-damaging agents, ATM kinase inhibition is thought to enhance radiochemotherapy efficacy. In this study, we investigated the roles of autophagy and reactive oxygen species (ROS) in modulating cytotoxicity induced by suppression of ATM kinase in head and neck cancer cells.
  
  
  METHODS
  We use KU55933 to inhibit ATM kinase activity. The cell viability was determined by MTT assays. Autophagy was examined by Western blot for LC3-II and microscopy for acidic vesicles and EGFP-LC3 punctate formation. DCF-DA staining and flow cytometry were used for analyzing ROS generation.
  
  
  RESULTS
  we found that KU55933 reduced cell viability in several head and neck cancer cell lines. KU55933-treated cells showed increased cytoplasmic vesicles, LC3-II accumulation, and EGFP-LC3 punctate formation, indicating that autophagy was induced. KU55933 also increased ROS generation, which was required for autophagy induction because the ROS scavenger N-acetyl-L-cysteine could reduce LC3-II accumulation. KU55933-induced autophagy played a cytoprotective role against ROS-mediated cytotoxicity because autophagy inhibition by chloroquine augmented KU55933's cytotoxicity. In addition, KU55933 reduced cisplatin-resistant head and neck cancer cell viabilities, and induced LC3-II accumulation in these cells.
  
  
  CONCLUSIONS
  Together, these results shed light on KU55933's therapeutic values as well as autophagy inhibitors in treating primary and cisplatin-resistant head and neck cancers.
authors: Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan. csl@kmu.edu.tw
authors: Chang-Shen
authors: CS
authors: Lin
authors: Yu-Chu
authors: YC
authors: Wang
authors: Jau-Ling
authors: JL
authors: Huang
authors: Chi-Chun
authors: CC
authors: Hung
authors: Jeff Yi-Fu
authors: JY
authors: Chen
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D001343:Autophagy / Q000187:drug effects*; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000187:drug effects / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000378:metabolism*; D006801:Humans; D008853:Microscopy; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011753:Pyrones / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors
chemical_list: C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D009025:Morpholines; D011753:Pyrones; D017382:Reactive Oxygen Species; D025521:Tumor Suppressor Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases