In fact, since increased CLIC1 activity is a main regulator of cell proliferation in several tumors, including gastric, colon, and hepato-carcinomas (Peretti et al., 2015), and, of course, GBM (Wang et al., 2012; Setti et al., 2013; Gritti et al., 2014), this mechanism may reconcile the evidence of antitumor activity of metformin (and possibly of other biguanides) on such broad types of neoplasia. Here, CLIC1 is linked to neoplasm.