Glutamine drives glutathione synthesis and contributes to radiation sensitivity of A549 and H460 lung cancer cell lines

• Published in: Biochimica et biophysica acta Vol. 1860; no. 4; pp. 836 - 843
• Main Authors: Sappington, Daniel R., Siegel, Eric R., Hiatt, Gloria, Desai, Abhishek, Penney, Rosalind B., Jamshidi-Parsian, Azemat, Griffin, Robert J., Boysen, Gunnar
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.04.2016
• Subjects: A549; carbon; cell growth; Cell Line, Tumor; cell proliferation; cytotoxicity; excretion; glutamic acid; Glutaminase; glutamine; Glutamine - metabolism; Glutamine utilization; glutathione; Glutathione - metabolism; Glutathione synthesis; H460; Humans; lung neoplasms; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Lung Neoplasms - radiotherapy; neoplasm cells; nitrogen; Radiation Tolerance; sulfides; Sulfides - pharmacology; Thiadiazoles - pharmacology; viability; X-Rays; BPTES; H460; A549; Glutathione synthesis; LC–MS/MS; Glutaminase; GLS; Glutamine utilization
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2016.01.021

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. 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. A significant correlation between glutamine consumption and glutathione excretion was demonstrated in H460 and A549 tumor cells. Culturing in the presence of [13C5]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. 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. Glutamine is essential for synthesis and excretion of glutathione to promote cell growth and viability. Glutathione synthesis is dependent on available glutamine and glutaminase activity.•Lung tumor cells excrete large amounts of glutathione, questioning its role as an antioxidant.•Glutamine-derived glutathione plays an important role in radiation sensitivity.