Neutrophils are immune cells that play a major role in the innate immune response. They can be polarized into immunosuppressive neutrophils under stress, inflammatory, and cancer conditions, promoting tumor development and infiltration. It is important for development of cancer therapies to understand the mechanism of differentiation and functional regulation of neutrophil subsets. Neutrophils secrete various peptides and proteins, including defensins to attack invading pathogens upon activation. Carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) family members play an important role in intercellular interactions which regulates biological functions of neutrophils.

In this study, we demonstrated that PPM1D regulates differentiation and polarization of neutrophil. Inhibition of PPM1D induced neutrophil-differentiation. Interestingly, the PPM1D inhibited cells showed different neutrophil-functions, decreased phagocytotic activity and increased production of inflammatory cytokines, compared with differentiated HL-60 in the absence of SL-176. The results suggested that PPM1D-inhibited cells differentiated into a unique neutrophil-subset with different functions. We performed transcriptome analysis and found that the splicing pattern of genes involved in inflammatory response and lipid metabolism is altered in the PPM1D-inhibited cells. We found that the CEACAM3, a CEACAM family member showed different splicing pattern in the PPM1D-inhibited cells compared with differentiated HL-60 cells. PPM1D-inhibited cells expressed two splice variants: CEACAM3, consisting of 252 amino acid residues and sCEACAM3, consisting of 177 amino acid residues. sCEACAM3 shares the N-terminal 141 amino acid residues with CEACAM3 and the C-terminal region including transmembrane domain (TM) was replaced by a specific sequence. We found that sCEACAM3 was secreted extracellularly and affected function of neutrophils, unlike full-length CEACAM3, which is localized in the cell membrane. Together, it is suggested that PPM1D plays important roles on neutrophil-differentiation and subset polarization via splicing control of CEACAM3.Our data suggests that CEACAM3-derived peptides may have promising role for regulating neutrophil-function.