Our results thus demonstrate that in vivo, MCF7-si cells proliferate more effectively and more rapidly than MCF7-wt cells, and together with the notions that it activates p53 [10,11], inactivates Cdk2 and Cdk6 [12,13], inhibits TGFβ signaling [14] and induces (endothelial cell) apoptosis [15,16], they suggest that PP2Cα may possess tumor-suppressing properties. The gene discussed is CDK6; the disease is neoplasm.