Metformin suppresses cancer cell proliferation independent of metabolic checkpoints.

<p>Cells were cultured with the indicated concentrations of metformin, and cell number was determined by crystal violet incorporation after 72 h of culture. Cell number is expressed relative to control cell number (no metformin) at 72 h. Shown are cell numbers for control (WT) and AMPKα-deficient (KO) MEFs (<b>A</b>), control (WT) and LKB1-deficient (KO) MEFs (<b>B</b>), A549 cells expressing empty vector (A549/Vec) or re-expressing LKB1 (A549/LKB1) (<b>C</b>), and control (WT) or 4EBP1/2-deficient (double knockout, DKO) MEFs (<b>D</b>) in response to metformin treatment. Each data point represents the mean ± SEM for triplicate samples. Raw data for this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002309#pbio.1002309.s002" target="_blank">S2 Data</a>.