Inhibition of Ser/Thr phosphatase PPM1D induces neutrophil differentiation in HL-60 cells.

Protein phosphatase Magnesium-dependent 1, Delta (PPM1D) is a wild-type p53-inducible Ser/Thr phosphatase that acts as a negative regulator of the p53 tumor suppressor. Gene amplification and overexpression of PPM1D have been reported in various cancers including leukemia and neuroblastoma. Therefore, PPM1D is a promising target in cancer therapy. It has been reported that PPM1D knockout mice exhibit neutrophilia in blood and show a defective immune response. Here, we found that inhibition of PPM1D induced neutrophil differentiation of human promyelocytic leukemia cell line HL-60. The combination of a PPM1D inhibitor and all-trans retinoic acid significantly increased their differentiation efficiency. The PPM1D inhibitor also induced G1 arrest in HL-60 cells. Our results suggest that PPM1D may be a potential therapeutic target for blood cell diseases including leukemia.