MM cells are sensitive to Gln depletion. (A) HMCLs were treated with increasing concentrations of BPTES or vehicle (−). After 48 hours, cell viability was assessed, and data were expressed as % of the value obtained with cells treated with the vehicle. (B) HMCLs were treated with increasing concentrations of CB-839 or vehicle (−). After 48 hours, cell viability was assessed, and data were expressed as % of the value obtained with cells treated with the vehicle. (C) HMCLs were incubated with decreasing concentrations of Gln in the absence or in the presence of the GS inhibitor methionine-sulfoximine (1 mM). After 48 hours, cell viability was assessed, and data were expressed as % of the cell growth observed at 4 mM Gln. (D) Cell contents of Gln, Glu, and 2-OG were measured by liquid chromatography tandem mass spectrometry in RPMI 8226 incubated for 19 hours in the presence (4 mM) or in the absence of Gln. Data were expressed as nmol/mg protein. (E) RPMI 8226 were incubated in the presence (4 mM) or in the absence of Gln with or without dimethyl-2-OG (8 mM). After 24 hours, the expression of the apoptosis marker Apo 2.7 was checked by flow cytometry. (F) MM cells were incubated in the presence (4 mM) or in the absence of Gln with or without dimethyl-2-OG (8 mM). After 48 hours, cell viability was assessed, and data were expressed as % of control (Gln present, 2-OG absent). For panels A-F, data are means ± SD of 3 experiments with 3 determinations each. *P < .05, ***P < .001 vs control.