Figure 1.

Metabolic characterization of GBM tumor cells in vitro. A, ECAR measurements. There were no significant differences between A11 and U87 cells (P = 0.427) or between S2 and AT5 cells (P = 0.494). B, OCR measurements. There were no significant differences between S2 and AT5 cells (P = 0.920) or between A11 and U87 cells (P = 0.127). C, OCR/ECAR ratio. There were no significant differences between S2 and AT5 cells (P = 0.996) or between A11 and U87 cells (P = 0.378). D,²H MRS measurements of ²H-labeled lactate produced by A11, S2, and AT5 cells incubated for 4 hours in glucose-free neurobasal media and U87 cells incubated in glucose-free DMEM, both supplemented with 10 mmol/L [6,6′-²H₂]glucose. E and F, HSQC ¹H-¹³C MRS measurements of ¹³C-labeled lactate (E) and Glx (F) measured in cell extracts obtained by chloroform–methanol extraction following incubation for 6 hours in glucose-free media supplemented with 10 mmol/L [U-¹³C]glucose. Proton signal intensities in the spectra are reported relative to the TMSP standard. ns, not significant; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.