Glutamine metabolism in cancer cells and its regulation by oncogenes and tumor suppressors. After glutamine is imported into the cell through surface transporters such as ASCT1 or SN2, the majority of it either donates nitrogen to macromolecules, or is deamidated by glutaminases, which remove the γ-nitrogen to form glutamate (Glu). Glu can be used for glutathione (GSH) biosynthesis, or processed further in the mitochondria, where removal of the α-nitrogen by aminotransferases or glutamate dehydrogenase (GDH) produces α-ketoglutarate (α-KG). Expression of glutaminases (GLS, GLS2) is upregulated by c-Myc and p53, respectively. Expression of glutamine synthetase (GS) is driven by β-catenin (β-cat). Abbreviations, Ac-CoA, acetyl-CoA; ALT, alanine aminotransferase; AST, aspartate aminotransferase; Cit, citrate; OAA, oxaloacetate; Pyr, pyruvate; TCA, tricarboxylic acid.