PURPOSE: Mitochondrial mutations have been identified in head and neck squamous cell carcinoma (HNSCC), but the pathways by which phenotypic effects of these mutations are exerted remain unclear. Previously, we found that mitochondrial ND2 mutations in primary HNSCC increased reactive oxygen species (ROS) and conferred an aerobic, glycolytic phenotype with HIF1alpha accumulation and increased cell growth. The purpose of the present study was to examine the pathways relating these alterations. EXPERIMENTAL DESIGN: Mitochondrial mutant and wild-type ND2 constructs were transfected into oral keratinocyte immortal cell line OKF6 and head and neck cancer cell line JHU-O19 and established transfectants. The protein levels of HIF1alpha, pyruvate dehydrogenease (PDH), phosphorylated PDH, and pyruvate dehydrogenease kinase 2 (PDK2), together with ROS generation, were compared between the mutant and the wild type. Meanwhile, the effects of small molecule inhibitors targeting PDK2 and mitochondria-targeted catalase were evaluated on the ND2 mutant transfectants. RESULTS: We determined that ND2 mutant down-regulated PDH expression via up-regulated PDK2, with an increase in phosphorylated PDH. Inhibition of PDK2 with dichloroacetate decreased HIF1alpha accumulation and reduced cell growth. Extracellular treatment with hydrogen peroxide, a ROS mimic, increased PDK2 expression and HIF1alpha expression, and introduction of mitochondria-targeted catalase decreased mitochondrial mutation-mediated PDK2 and HIF1alpha expression and suppressed cell growth. CONCLUSIONS: Our findings suggest that mitochondrial ND2 mutation contributes to HIF1alpha accumulation via increased ROS production, up-regulation of PDK2, attenuating PDH activity, thereby increasing pyruvate, resulting in HIF1alpha stabilization. This may provide insight into a potential mechanism, by which mitochondrial mutations contribute to HNSCC development.
PURPOSE: Mitochondrial mutations have been identified in head and neck squamous cell carcinoma (HNSCC), but the pathways by which phenotypic effects of these mutations are exerted remain unclear. Previously, we found that mitochondrial ND2 mutations in primary HNSCC increased reactive oxygen species (ROS) and conferred an aerobic, glycolytic phenotype with HIF1alpha accumulation and increased cell growth. The purpose of the present study was to examine the pathways relating these alterations. EXPERIMENTAL DESIGN: Mitochondrial mutant and wild-type ND2 constructs were transfected into oral keratinocyte immortal cell line OKF6 and head and neck cancer cell line JHU-O19 and established transfectants. The protein levels of HIF1alpha, pyruvate dehydrogenease (PDH), phosphorylated PDH, and pyruvate dehydrogenease kinase 2 (PDK2), together with ROS generation, were compared between the mutant and the wild type. Meanwhile, the effects of small molecule inhibitors targeting PDK2 and mitochondria-targeted catalase were evaluated on the ND2 mutant transfectants. RESULTS: We determined that ND2 mutant down-regulated PDH expression via up-regulated PDK2, with an increase in phosphorylated PDH. Inhibition of PDK2 with dichloroacetate decreased HIF1alpha accumulation and reduced cell growth. Extracellular treatment with hydrogen peroxide, a ROS mimic, increased PDK2 expression and HIF1alpha expression, and introduction of mitochondria-targeted catalase decreased mitochondrial mutation-mediated PDK2 and HIF1alpha expression and suppressed cell growth. CONCLUSIONS: Our findings suggest that mitochondrial ND2 mutation contributes to HIF1alpha accumulation via increased ROS production, up-regulation of PDK2, attenuating PDH activity, thereby increasing pyruvate, resulting in HIF1alpha stabilization. This may provide insight into a potential mechanism, by which mitochondrial mutations contribute to HNSCC development.
Authors: N S Chandel; D S McClintock; C E Feliciano; T M Wood; J A Melendez; A M Rodriguez; P T Schumacker Journal: J Biol Chem Date: 2000-08-18 Impact factor: 5.157
Authors: Noan-Minh Chau; Paul Rogers; Wynne Aherne; Veronica Carroll; Ian Collins; Edward McDonald; Paul Workman; Margaret Ashcroft Journal: Cancer Res Date: 2005-06-01 Impact factor: 12.701
Authors: Edwin P Hui; Anthony T C Chan; Francesco Pezzella; Helen Turley; Ka-Fai To; Terence C W Poon; Benny Zee; Frankie Mo; Peter M L Teo; Dolly P Huang; Kevin C Gatter; Philip J Johnson; Adrian L Harris Journal: Clin Cancer Res Date: 2002-08 Impact factor: 12.531
Authors: Vlad C Sandulache; Heath D Skinner; Thomas J Ow; Aijun Zhang; Xuefeng Xia; James M Luchak; Lee-Jun C Wong; Curtis R Pickering; Ge Zhou; Jeffrey N Myers Journal: Cancer Date: 2011-06-30 Impact factor: 6.860
Authors: Yan Guo; Qiuyin Cai; David C Samuels; Fei Ye; Jirong Long; Chung-I Li; Jeanette F Winther; E Janet Tawn; Marilyn Stovall; Päivi Lähteenmäki; Nea Malila; Shawn Levy; Christian Shaffer; Yu Shyr; Xiao-Ou Shu; John D Boice Journal: Mutat Res Date: 2012-02-24 Impact factor: 2.433
Authors: Giuseppe Gasparre; Anna Maria Porcelli; Giorgio Lenaz; Giovanni Romeo Journal: Cold Spring Harb Perspect Biol Date: 2013-02-01 Impact factor: 10.005