title: Glutamine drives glutathione synthesis and contributes to radiation sensitivity of A549 and H460 lung cancer cell lines.
abstract: BACKGROUND
  Increased glutamine uptake is known to drive cancer cell proliferation, making tumor cells glutamine-dependent. Glutamine provides additional carbon and nitrogen sources for cell growth. The first step in glutamine utilization is its conversion to glutamate by glutaminase (GLS). Glutamate is a precursor for glutathione synthesis, and we investigated the hypothesis that glutamine drives glutathione synthesis and thereby contributes to cellular defense systems.
  
  
  METHODS
  The importance of glutamine for glutathione synthesis was studied in H460 and A549 lung cancer cell lines using glutamine-free medium and bis-2-(5-phenyl-acetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES) a GLS inhibitor. Metabolic activities were determined by targeted mass spectrometry.
  
  
  RESULTS
  A significant correlation between glutamine consumption and glutathione excretion was demonstrated in H460 and A549 tumor cells. Culturing in the presence of [(13)C5]glutamine demonstrated that by 12h >50% of excreted glutathione was derived from glutamine. Culturing in glutamine-free medium or treatment with BPTES, a GLS-specific inhibitor, reduced cell proliferation and viability and abolished glutathione excretion. Treatment with glutathione-ester prevented BPTES-induced cytotoxicity. Inhibition of GLS markedly radiosensitized the lung tumor cell lines, suggesting an important role of glutamine-derived glutathione in determining radiation sensitivity.
  
  
  CONCLUSIONS
  We demonstrate here for the first time that a significant amount of extracellular glutathione is directly derived from glutamine. This finding adds yet another important function to the already known glutamine dependence of tumor cells and probably tumors as well.
  
  
  CONCLUSIONS
  Glutamine is essential for synthesis and excretion of glutathione to promote cell growth and viability.
authors.affiliation: Department of Environmental and Occupational Health, 4301 W. Markham Street Slot #820, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Sappington
authors.affiliation: Department of Biostatistics, 4301 W. Markham Street Slot #516, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Siegel
authors.affiliation: Department of Environmental and Occupational Health, 4301 W. Markham Street Slot #820, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Gloria
authors.initials: G
authors.lastname: Hiatt
authors.affiliation: Department of Environmental and Occupational Health, 4301 W. Markham Street Slot #820, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Desai
authors.affiliation: Department of Environmental and Occupational Health, 4301 W. Markham Street Slot #820, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Rosalind B
authors.initials: RB
authors.lastname: Penney
authors.affiliation: Department of Radiation Oncology, 4301 W. Markham Street, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Azemat
authors.initials: A
authors.lastname: Jamshidi-Parsian
authors.affiliation: Department of Radiation Oncology, 4301 W. Markham Street, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; The Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Griffin
authors.affiliation: Department of Environmental and Occupational Health, 4301 W. Markham Street Slot #820, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; The Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. Electronic address: gboysen@uams.edu.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Boysen
mesh_terms: D045744:Cell Line, Tumor; D005973:Glutamine / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D011836:Radiation Tolerance; D013440:Sulfides / Q000494:pharmacology; D013830:Thiadiazoles / Q000494:pharmacology; D014965:X-Rays
chemical_list: D013440:Sulfides; D013830:Thiadiazoles; C523193:bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide; D005973:Glutamine; D005978:Glutathione
keywords: A549; Glutaminase; Glutamine utilization; Glutathione synthesis; H460
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