Increased glutamine uptake is known to drive cancer cell proliferation, making tumor cells glutamine-dependent. Studying lymph node aspirates containing malignant lung tumor cells showed a strong correlation between glutamine consumption and glutathione (GSH) excretion. Subsequent validation in A549 and H460 lung tumor cell lines provided additional evidence that glutamine drives GSH synthesis and excretion at μmolar amounts. Surprisingly, using stable isotope labeled glutamine as tracer metabolite, demonstrated that the glutamate group in GSH is directly derived from glutamine, linking glutamine utilization to GSH syntheses. To understand the possible mechanistic link between glutamine consumption and GSH excretion we studied GSH metabolism in more detail. Inhibition of glutaminase with BPTES and CB-839, two known inhibitors, essentially abolished GSH synthesis and excretion in lung tumor cells. Inhibition of glutaminase markedly radiosensitizes the lung tumor cell lines, suggesting an important role of glutamine-derived GSH in determining radiation sensitivity. In subsequent mouse xenografts, short term CB-839 treatment reduced serum GSH by &gt;50% and increases response to radiation therapy of H460 derived tumors by 30%, suggesting a clinical relevant mechanism. GSH is the most abundant and most widely studied endogenous antioxidant and concentrations in tumor tissue have been reported to be as high a 10 mM. Extracellular GSH is metabolized by γ-glutamyl-transferase (GGT) to various γ-glutamyl-amino acid derivates. Further analysis of our clinical specimens and cell culture media and cell samples showed presence of various γ-glutamyl-amino acids. To elucidate why lung tumor cells excrete large amounts of GSH and make γ-glutamyl-amino acids we incubated none-transformed NIH3T3 and small airway epithelial cells (SAEC) with GSH and γ-glutamyl-glutamine. γ-Glutamyl-glutamine induced transformations in both cell lines, while GSH induced transformations only in GGT positive SAEC. Together these results provide evidence that lung tumors utilize glutamine to promote GSH synthesis to increase defense against radiation injury and excrete GSH to recruit neighboring cells producing a heterogeneous tumor phenotype.

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

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.