TGF-β1in Gastric Cancer Microenvironment Influence TAM Phenotype By Regulating The Expression Of MiR-155in The TAM

Objective:To explore the possible regulation mechanisms of gastric tumor-associated macrophage phenotype changes, we studied the effect of TGF-β1from gastric cancer microenviroment on the expression of miR-155in tumor-associated macrophages, and the effect of the miR-155expression on TAM phenotype.Methods:1. In order to observe the correlation between the TGF-β1expression and M2macrophage infiltration in gastric cancer tissues, we detected the expression of TGF-β1and M2macrophage cell surface molecules CD163in human gastric cancer tissues and normal gastric tissue by immunohistochemistry.2. In order to clarify miR-155expression in gastric tumor-associated macrophages and the possible regulation mechanism causing miR-155alteration, we performed the following experiments:first, we induced THP-1into macrophage by PMA, and got gastric tumor associated macrophages by gastric carcinoma cell culture supernatants stimulating macrophages; then we detected the expression of miR-155in macrophages using qRT-PCR, and compared the differential expression of miR-155in macrophage, TAM and macrophage after TGF-β1stimulus; at last, we used TGF-β1receptor blocker stimulated gastric tumor associated macrophages, and detected the expression of miR-155using qRT-PCR.3. In order to observe the effect of miR-155on TAM phenotype:we constructed miR-155plasmid, transfected it into macrophage, then we detected the levels of IL-10and IL-12in the supernate of macrophage using ELISA.Results:1. Immunohistochemical results showed that, as the marker of macrophage surface molecules, CD163mainly expressed in the cell membrane of macrophages, and as a growth factor, TGF-β1expressed mainly in the cytoplasm of tumor cells, we also found that expression of TGF-β1and CD163in gastric cancer were higher than in normal gastric tissue, statistical analysis showed that expression of TGF-β1and CD163was positively correlated.2. Expression of miR-155in TAM was lower than in macrophage with no stimulation by gastric carcinoma cell culture supernatants, stimulating by TGF-β1also decreased the level of miR-155in macrophage. Inhibiting the action of TGF-β1by TGF-β1receptor blocker can retrieve the expression of miR-155in TAM.3. Levels of IL-10in the supernate of macrophage transfected by miR-155plasmid was lower than in macrophage transfected by empty plasmid, but IL-12was otherwise.Conclusions:MiR-155has the potential of inducing macrophages into M1macrophage, while TGF-β1secreted by gastric cancer cells can decrease miR-155expression in macrophages, which suggest that TGF-β1in gastric cancer microenvironment decreased the expression of miR-155in TAM, thereby induced TAM into M2macrophage.