CASP3 and neoplasm: Specifically, quantification of Ki67 and active caspase-3 positive cells reveals that metformin treatment significantly reduces tumor growth and cell proliferation (Ki67) by 3.5-fold and 2-fold within U87 and LN18 tumors, and increases tumor cell death (active caspase-3) by 4-fold and 6-fold within U87 and LN18 tumors, respectively (Fig 6F and S5E Fig).