Consistent with the in vitro data, in an in vivo nude mice model in which tumor xenografts were developed by injecting MCF7 cells into the mice, the combination treatment using metformin (2 mg/mL in drinking water) and tamoxifen (60 mg/kg by oral gavage) caused tumor growth arrest, reduction in tumor weight, and decrease in the expression/levels of Ki-67, phospho-AMPK, phospho-mTOR, and phospho-p70S6K [103]. This evidence concerns the gene MKI67 and neoplasm.