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Illustration showing uptake mechanism and assimilation process of nutrient-based PET agents. See also main text. The grey box represents the cytoplasm, while the yellow box represents mitochondria. Green arrows represent metabolic route of specific PET agent, while black arrows represent metabolic route of associated nutrient / building block, and green-black arrows a similar route for PET agent and nutrient / building block. Red text / arrows show brain tumor cell-specific metabolic alterations. Of note, although ¹¹C-MCYS is a derivative of the amino acid cysteine, it is analogous to ¹¹C-MET and therefore grouped together with ¹¹C-MET in this illustration.
Abbreviations: LAT, large neutral amino acid transporter; IDO, indoleamine 2,3-dioxygenase; ASCT, anti-neutral amino acid transporter; CKα, choline kinase alpha; CoA, acyl coenzyme A; G6P, glucose-6-phosphate; HIF, hypoxia-inducible factors; IDH, isocitrate dehydrogenase; PEP, phosphoenolpyruvate; PKM2, pyruvate kinase M2; PROT, proline transporter; SMCT, Na⁺ monocarboxylate cotransporter; MCT, monocarboxylate transporter; CHT1, high-affinity choline transporter; CTL, choline transporter-like protein; OCT / OCTN, organic cation transport proteins; GLUT, glucose transporter; SGLT, sodium-glucose linked transporter; TCA, tricarboxylic acid.