Inflammatory Molecule, PSGL-1, Deficiency Activates Macrophages to Promote Colorectal Cancer Growth Through NF-kappaB Signaling

P-selectin glycoprotein ligand 1 (SELPLG/ PSGL-1 ) is an inflammatory molecule that is functionally related to immune cell differentiation and leukocyte mobilization. However, the role of PSGL-1 in tumor development remains unknown. Therefore, this study investigates the mechanistic role of PSGL-1 in the development of intestinal tumors in colorectal cancer. Apc Min/+ mice are highly susceptible to spontaneous intestinal adenoma formation, and were crossbred with PSGL1-null mice to generate compound transgenic mice with a Apc Min/+ ; PSGL-1 −/− genotype. The incidence and pathologic features of the intestinal tumors were compared between the Apc Min/+ mice and Apc Min/+ ; PSGL-1 −/− mice. Importantly, PSGL-1 –deficient mice showed increased susceptibility to develop intestinal tumors and accelerated tumor growth. Mechanistically, increased production of the mouse chemokine ligand 9 (CCL9/MIP-1γ) was found in the PSGL-1 –deficient mice, and the macrophages are likely the major source of macrophage inflammatory protein-1 gamma (MIP-1γ). Studies in vitro demonstrated that macrophage-derived MIP-1γ promoted colorectal cancer tumor cell growth through activating NFκB signaling. Conversely, restoration of the PSGL-1 signaling via bone marrow transplantation reduced MIP-1γ production and attenuated the ability of Apc Min/+ ; PSGL-1 −/− mice to generate intestinal tumors. In human colorectal cancer clinical specimens, the presence of PSGL-1 –positive cells was associated with a favorable tumor–node–metastasis staging and decreased lymph node metastasis. Implications: PSGL-1 deficiency and inflammation render intestinal tissue more vulnerable to develop colorectal tumors through a MIP-1γ/NFκB signaling axis. Mol Cancer Res; 15(4); 467–77. ©2017 AACR .