title: High mitochondrial DNA copy number and bioenergetic function are associated with tumor invasion of esophageal squamous cell carcinoma cell lines.
abstract: We previously reported a gradual increase of relative mitochondrial DNA (mtDNA) copy number during the progression of esophageal squamous cell carcinoma (ESCC). Because mitochondria are the intracellular organelles responsible for ATP production, we investigated the associations among mtDNA copy number, mitochondrial bioenergetic function, tumor invasion and the expression levels of epithelial mesenchymal transition (EMT) markers in a series of seven ESCC cell lines, including 48T, 81T, 146T, TE1, TE2, TE6 and TE9. Among them, TE1 had the highest relative mtDNA copy number of 240.7%. The mRNA of mtDNA-encoded ND1 gene (2.80), succinate-supported oxygen consumption rate (11.21 nmol/min/10(6) cells), ATP content (10.7 fmol/cell), and the protein level of mitochondrial transcription factor A (TFAM) were the highest and the lactate concentration in the culture medium (3.34 mM) was the lowest in TE1. These findings indicate that TE1 exhibited the highest bioenergetic function of mitochondria. Furthermore, TE1 showed the highest trans-well migration activity of 223.0 cells/field, the highest vimentin but the lowest E-cadherin protein expression levels, which suggest that TE1 had the highest invasion capability. We then conducted a knockdown study using pLKO.1-based lentiviral particles to infect TE1 cells to suppress the expression of TFAM. Molecular analyses of the parental TE1, control TE1-NT and TFAM knockdown TE1-sh-TFAM(97) cells were performed. Interestingly, as compared to the control TE1-NT, TE1-sh-TFAM(97) exhibited lower levels of the relative mtDNA copy number (p = 0.001), mRNA of mtDNA-encoded ND1 gene (p = 0.050), succinate-supported oxygen consumption rate (p = 0.065), and ATP content (p = 0.007), but had a higher lactate concentration in the culture medium (p = 0.010) and higher protein level of lactate dehydrogenase. A decline in mitochondrial bioenergetic function was observed in TE1-sh-TFAM(97). Significantly, compared to the control TE1-NT, TE1-sh-TFAM(97) had a lower trans-well migration activity (p < 0.001), a higher E-cadherin level but a lower vimentin protein level, which indicates a decrease of invasiveness. Taken together, we suggest that high relative mtDNA copy number and bioenergetic function of mitochondria may confer an advantage for tumor invasion of ESCC.
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Faculty of Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Division of Thoracic Surgery, Department of Surgery, Taipei Hospital, Department of Health, Executive Yuan, New Taipei City 242, Taiwan.
authors.forename: Chen-Sung
authors.initials: CS
authors.lastname: Lin
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Faculty of Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Division of Allergy, Immunology and Rheumatology, Department of Internal Medicine, Wan-Fang Hospital, Taipei Medical University, Taipei 116, Taiwan.
authors.forename: Hui-Ting
authors.initials: HT
authors.lastname: Lee
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Taipei Hospital, Department of Health, Executive Yuan, New Taipei City 242, Taiwan.|Department of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Shu-Yu
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan.|Department of Life Science and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Yao-An
authors.initials: YA
authors.lastname: Shen
authors.affiliation: Division of Thoracic Surgery, Department of Surgery, Taipei Medical University-Shuang Ho Hospital, New Taipei 235, Taiwan.
authors.forename: Liang-Shun
authors.initials: LS
authors.lastname: Wang
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Department of Life Science and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Yann-Jang
authors.initials: YJ
authors.lastname: Chen
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Faculty of Medicine, National Yang-Ming University, Taipei 112, Taiwan.|Department of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan.|Department of Medicine, Mackay Medical College, New Taipei City 252, Taiwan.
authors.forename: Yau-Huei
authors.initials: YH
authors.lastname: Wei
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004272:DNA, Mitochondrial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D018450:Disease Progression; D004734:Energy Metabolism / Q000235:genetics*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000077277:Esophageal Squamous Cell Carcinoma; D018628:Gene Dosage / Q000235:genetics*; D055785:Gene Knockdown Techniques; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics; D009361:Neoplasm Invasiveness / Q000235:genetics; D010101:Oxygen Consumption / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014746:Vimentin / Q000378:metabolism
chemical_list: D015820:Cadherins; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; D014157:Transcription Factors; D014746:Vimentin; C422562:mitochondrial transcription factor A; D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase
keywords: bioenergetic function; epithelial mesenchymal transition (EMT); esophageal squamous cell carcinoma (ESCC); invasion; mitochondrial DNA (mtDNA)