title: Chronic CSE treatment induces the growth of normal oral keratinocytes via PDK2 upregulation, increased glycolysis and HIF1α stabilization.
abstract: BACKGROUND
  Exposure to cigarette smoke is a major risk factor for head and neck squamous cell carcinoma (HNSCC). We have previously established a chronic cigarette smoke extract (CSE)-treated human oral normal keratinocyte model, demonstrating an elevated frequency of mitochondrial mutations in CSE treated cells. Using this model we further characterized the mechanism by which chronic CSE treatment induces increased cellular proliferation.
  
  
  RESULTS
  We demonstrate that chronic CSE treatment upregulates PDK2 expression, decreases PDH activity and thereby increases the glycolytic metabolites pyruvate and lactate. We also found that the chronic CSE treatment enhanced HIF1α accumulation through increased pyruvate and lactate production in a manner selectively reversible by ascorbate. Use of a HIF1α small molecule inhibitor blocked the growth induced by chronic CSE treatment in OKF6 cells. Furthermore, chronic CSE treatment was found to increase ROS (reactive oxygen species) production, and application of the ROS scavengers N-acetylcysteine abrogated the expression of PDK2 and HIF1α. Notably, treatment with dichloroacetate, a PDK2 inhibitor, also decreased the HIF1α expression as well as cell proliferation in chronic CSE treated OKF6 cells.
  
  
  CONCLUSIONS
  Our findings suggest that chronic CSE treatment contribute to cell growth via increased ROS production through mitochondrial mutations, upregulation of PDK2, attenuating PDH activity thereby increasing glycolytic metabolites, resulting in HIF1α stabilization. This study suggests a role for chronic tobacco exposure in the development of aerobic glycolysis and normoxic HIFα activation as a part of HNSCC initiation. These data may provide insights into development of chemopreventive strategies for smoking related cancers.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America.
authors.forename: Wenyue
authors.initials: W
authors.lastname: Sun
authors.forename: Steven S
authors.initials: SS
authors.lastname: Chang
authors.forename: Yumei
authors.initials: Y
authors.lastname: Fu
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Califano
mesh_terms: D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D049109:Cell Proliferation; D006019:Glycolysis; D006258:Head and Neck Neoplasms; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000737:chemistry*; D015603:Keratinocytes / Q000166:cytology*; D009055:Mouth / Q000166:cytology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D055550:Protein Stability; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017382:Reactive Oxygen Species; D012906:Smoke / Q000009:adverse effects*; D015854:Up-Regulation / Q000235:genetics; D014026:Nicotiana
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C000631430:PDK2 protein, human; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D017382:Reactive Oxygen Species; D012906:Smoke; D017346:Protein Serine-Threonine Kinases