SGK1 and cancer: Figure 3A shows an example of the binding pose of metformin on kinase SGK1. Similar to other kinases, the binding site of metformin is adjacent to the ATP binding site9. It implies that metformin may act differently from the common ATP inhibitors of kinases. We further mapped somatic cancer mutations observed in COSMIC (cancer.sanger.ac.uk)20 onto the structures of putative kinase targets. A number of these mutations surround the metformin binding site. Five examples are shown in Fig. 3B–F. These amino acid mutations observed in COSMIC are listed in supplementary Table S1.