Fig. 5

Metformin can only induce cell death under glucose-deprived conditions. MCF-7 (a) and MDA-MB-231 (b) cells were plated in medium containing 11 mM or 2.75 mM glucose and were treated with indicated concentrations of metformin and everolimus for 4 days. In addition, cells plated in 2.75 mM glucose were also replenished with 2.75 mM glucose every day (2.75 mM glucose replenished). AnnexinV/PI staining was used to quantify the percentage of dead cells after 4 days. Glucose concentration in the culture medium was determined after 4 days. The dashed line indicates the detection limit of the glucose meter. Data are presented as mean ± SD of three different experiments. Treated samples were compared to the same glucose concentration control. * p < 0.05; ** p < 0.01; *** p < 0.001