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 [13C5]glutamine demonstrated that by 12 hrs >50% of excreted glutathione is derived from glutamine. Culturing in glutamine-free medium or treatment with BPTES, a glutaminase (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. General significance Glutamine is essential for synthesis and excretion of glutathione to promote cell growth and viability.

Reactive oxygen species (ROS) are a key determinant of cancer's metabolic phenotype

“…In addition, glutamine can be used to generate NADPH through the malate pathway, providing a multitude of substrates for the glutathione system. Inhibition of glutamine metabolism sensitizes lung cancer cells to radiation . Similarly, the folate pathway can also support detoxification through two mechanisms.…”

“…Inhibition of glutamine metabolism sensitizes lung cancer cells to radiation. 81 Similarly, the folate pathway can also support detoxification through two mechanisms. First, SHMT2 is involved in the synthesis of another glutathione precursor in glycine.…”

Integrated analysis of transcriptomic and metabolomic profiling reveal the p53 associated pathways underlying the response to ionizing radiation in HBE cells

“…The data are presented as the means ± SDs from three independent experiments; * p < 0.05 between different groups fibroblasts in response to γ-rays, by activating the p53 signaling pathway [61]. In glutathione metabolism, glutamine provides additional carbon and nitrogen for cell growth [62], thereby driving glutathione synthesis, and contributes to radiation sensitivity in lung cancer cell lines [62]. Glycolysis and gluconeogenesis have been extremely well characterized in many studies; during glycolysis, the glucose molecule is divided into two pyruvate molecules, which leads to the generation of lactate in cancer cells.…”

Highly Efficient Synthesis of Glutathione via a Genetic Engineering Enzymatic Method Coupled with Yeast ATP Generation

“…GSH can irreversibly bind to toxic electrophilic compounds that are to be eliminated outside the cell either spontaneously or via catalysis by glutathione s-transferase [5]. Related research shows that glutathione can be involved in DNA repair to protect against side effects caused by tumor drugs and other radiopharmaceuticals and radiotherapy [6,7]. In addition, glutathione has a skin-whitening effect in humans through the inhibition of melanogenesis by suppressing the activity of tyrosinase [8,9].…”