Figure 2.

AMPK activation by metformin is sensitive to extracellular glucose concentration and is closely correlated with the effects of metformin on stem-like glioma-initiating cells. (A): SJ28P3 cells cultured in the presence of the indicated concentrations of metformin for 3 days under the conventional stem cell culture condition (glucose concentration, 26.2 mM) were subjected to immunoblot analysis of the indicated proteins. (B–H): SJ28P3 cells were cultured with or without metformin (1 mM) for 3 days at the indicated glucose concentrations. The cells were then subjected to immunoblot analysis of the whole (B, D) and fractionated (C) cell lysates, to immunofluorescence analysis (E, F), to observation under a phase contrast microscope (G), or to sphere formation assay (H). Note that the exposure time for each protein is different from that of the corresponding protein in Figure 1C. The data in (F) and (H) represent means ± SD from three independent experiments. Scale bars = 100 μm (E, F) and 50 μm (G). *, p < .05. Abbreviations: ACC, acetyl-CoA carboxylase; AMPK, AMP-activated protein kinase; GFAP, glial fibrillary acidic protein; n.s., not statistically significant; PARP, poly(ADP-ribose) polymerase.