Figure 3: 14-3-3σ reduces glucose uptake of colorectal and breast cancer cells.

(a) Microscopic pictures show that loss of 14-3-3σ in HCT116 resulted in marked enhancement of glucose uptake. HCT116 WT (14-3-3σ^+/+) and HCT116 14-3-3σ^−/− cells were incubated with 2-NBDG, a green fluorescent glucose analogue that is commonly used to measure glucose uptake. 2-NBDG signals were captured using fluorescence microscopy. (b) Flow cytometry analysis indicates a significant increase in glucose uptake of 14-3-3σ-deficient cancer cells. In this experiment, HCT116 WT and HCT116 14-3-3σ^−/− cells were incubated with 2-NBDG for the indicated times. 2-NBDG signals were quantified using flow cytometry. Our data point out a considerable enhancement of glucose-import activity in cancer cells on 14-3-3σ suppression. (c) Restoring 14-3-3σ expression in 14-3-3σ-deficient cells decreased glucose uptake in a dose-dependent manner. HCT116 14-3-3σ^−/− cells were transfected with increasing amounts of pCMV5-Flag-14-3-3σ. 2-NBDG signals were quantified using a flow cytometer as in b. (d) Bar graph and statistical analysis of data shown in c. Data represent means±95% CI. ANOVA,*P<0.05. (e) Representative pictures from a fluorescence microscope for the experiment in c. Scale bar, 50 μm. Forced expression of 14-3-3σ in 14-3-3σ-null cancer cells reduced glucose uptake. (f) Induced 14-3-3σ decreased the expression of glucose transporter Glut1 on the cell membrane surface. Induced and noninduced cells were stained with specific anti-Glut1 antibodies conjugated with allophycocyanin (APC) fluorophore and analysed using flow cytometry. Bars represent means±95% CI; Student’s t-test, *P<0.05.