The Molecular Mechanism Of Myeloid-derived Suppressor Cells And Mast Cells Chemotaxising To Tumor And The Pro-tumor Effects

Objective:Inflammation is an important feature of the tumor microenvironment, there are many kinds and a large number of inflammatory cells in the tumor tissue, they played an important role in tumorigenesis, tumor growth, invasion, metastasis and immune suppression. This study will to explore the molecular mechanisms of the myeloid-derived suppressor cells and mast cells chemotaxising to the tumor tissues and their pro-tumor effects.Methods:(1) RT-PCR and Western-Blot assays to detect the expression of chemokine CCL2 in the tumor tissues from breast cancer, gastric cancer, ovarian cancer patients as well as mice melanoma and liver cancer tissues, at the same time to detect the expression of CCR2 which is the receptor of CCL2 in corresponding myeloid-derived suppressor cells. (2) Transwell experiment to detect the chemotaxis effects on myeloid-derived suppressor cells from the tumor tissues in vitro. (3) Flow cytometry assay to detect the ratio of myeloid-derived suppressor cells in the tumor tissues and spleen from CCR2 knockout tumor bearing mice. (4) Tumor growth assay to detect the influence of myeloid-derived suppressor cells on tumor growth in mice. (5) RT-PCR and Western-Blot assays to detect the expression of SCF in seven kinds of human tumor cell lines and tissues as well as five kinds of mouse tumor cell lines and tissues. (6) Transwell experiment and migration assay in vivo to detect the chemotaxis effects on mast cells from the tumor tissues. (7) Tumor growth assay to detect the influence of mast cells on tumor growth in mice. (8) Real-time PCR experiment to detect the influence of mast cells on the expression of inflammatory cytokines in tumor tissue. (9) Flow cytometry assay to detect the influence of mast cells on the number of Treg and Th17 in tumor tissue.Results:(1) Tumor tissues from the breast cancer, gastric cancer, ovarian cancer patients as well as mice melanoma and liver cancer all expressed CCL2, at the same time the corresponding myeloid-derived suppressor cells expressed CCR2 which is the receptor of CCL2. (2) The myeloid-derived suppressor cells could be chemotaxised by tumor tissues, and this effect could be inhibited by CCL2 or CCR2 neutralizing antibody. (3) The ratio of myeloid-derived suppressor cells in tumor tissue and spleen from the CCR2 knockout tumor bearing mice reduced compared to the wide type tumor bearing mice. (4) The pro-tumor effect of the myeloid-derived suppressor cells from CCR2 knockout mice was significantly decreased. (5) The seven kinds of human tumor cell lines and tissues as well as five kinds of mouse tumor cell lines and tissues detected all expressed SCF. (6) The tumor tissues had the chemotactic effects on mast cells in vitro and in vivo, and this role could be inhibited by SCF or c-Kit neutralizing antibody or siRNA silenced the SCF expression in tumor cells. (7) Mast cells could promote tumor growth in vivo, and this effect could be inhibited by SCF or c-Kit neutralizing antibody or SCF siRNA. (8) Mast cells could promote the expression of IL-10 and TGF-βbut inhibit the expression of IL-2 in tumor tissue. (9) Mast cells could increase the number of Treg and Th17 in tumor tissue.Conclusions:The CCL2/CCR2 pathway mediated the myeloid-derived suppressor cells chemotaxising to tumor tissues and promoted tumor growth, The SCF/c-Kit pathway mediated mast cells chemotaxising to tumor tissues, promoted tumor growth and immune suppression.