Fig. 2
Increased glucose and lactate utilization fuels 5-FU resistance in 5-FU-R CRC cells. a 2-NBDG uptake by 5-FU-R and WT cells. Results are for mean MFI (FITC channel) ± SEM. b Tumor-bearing mice were injected with 10 nmol IRDye 800CW 2-DG Optical Probe via the tail vein and imaged 24 h later to determine in vivo glucose uptake. c Western blots of GLUTs in WT and 5-FU-R CRC cells. β-Actin was used as the internal reference. d Cell viability was measured by CCK8 assays on treatment with 10 μM STF-31 for 48 h. e Relative 5-FU sensitivity of 5-FU-R CRC cells flow-sorted for high and low membrane GLUT1 expression, compared with unsorted WT and 5-FU-R CRC cells as determined by CCK8 assays. Cells were cultured with 10− 5 M 5-FU for 72 h. f Lactate release from 5-FU-R cells relative to WT cells detected by colorimetry. Normalized lactate release counts using the total protein concentrations. g Tumor lactate concentrations of WT and 5-FU-R cell-bearing nude mice were quantified with MRS. Lactate resonance appears at 1.33 ppm. h Western blots of MCTs in WT and 5-FU-R cells. β-Actin was used as the internal reference. i Cell viability was measured by CCK8 assays on treatment with 0.5 μM AZD3965 or 1 μM Syrosingopine or both together for 72 h. j Relative 5-FU sensitivity of 5-FU-R CRC cells flow-sorted for high and low membrane MCT4 expression, compared with unsorted WT and 5-FU-R CRC cells as determined by CCK8 assays. Cell were cultured with 10− 5 M 5-FU for 72 h. k Effect of glucose deprivation or exogenous lactate supplementation on the survival of WT and 5-FU-R cells. Different concentrations of glucose and lactate were added to the culture medium for 48 h. WT or 5-FU-R cells cultured in normal complete RPMI-1640 medium were used as a baseline. For all studies n ≥ 3. Data are presented as means ± SEM. Bar chart data were compared by Student’s t-test or ANOVA (ns = not significant, * p < 0.05, ** p < 0.01, and *** p < 0.001)