Cells were grown in glutamine and glucose-free RPMI, supplemented either with dos mmol/L 13 C₅ or 15 N₂-glutamine or 5 mmol/L 13 C_six– d -glucose (Cambridge Isotope Laboratories), 10% dialyzed FBS, and 1% antibiotics (penicillin–streptomycin). After 24-hour growth, metabolites were extracted with methanol: acetonitrile: water (5:3:2) and the lysates were rotated at 4°C for 10 minutes and centrifuged at 14,000 ? g for 10 minutes at 4°C. For exometabolome, the cells were cultured in with 2 mmol/L glutamine and 25 mmol/L glucose for 72 hours. Exometabolome was extracted with acetonitrile: water (4:1), vortexed vigorously, and centrifuged at 14,000 ? g for 10 minutes at 4°C. LC separation of metabolites was performed using SeQuant ZIC-pHILIC (150 ? 2.1 mm, 5 ?mol/L) connected to a SeQuant ZIC-pHILIC guard column (20 ? 2.1 mm, 5 ?mol/L; Merck) with a flow rate 0.1 mL/minute on the Ultimate 3000 UHPLC (Dionex, Thermo Scientific), with buffer A (95% acetonitrile) and buffer B (50 mmol/L ammonium carbonate, pH 10, 5% acetonitrile).Continue reading→