Cell cycle and apoptosis analysis revealed that CSTP1 overexpression inhibited cancer cells to go through the cell cycle and sensitized bladder cancer cells to chemotherapy drugs, and depletion of PP2Ac domain abrogated the growth-inhibition and death-promotion ability of CSTP1, suggesting that CSTP1 exerted its tumor suppression function through inhibiting cell cycle progression and promoting cell apoptosis., and that protein phosphatase activity of CSTP1 plays a crucial role in its tumor suppression activity. This evidence concerns the gene PPP2CA and urinary bladder cancer.