The Effect Of A Small Molecular Inhibitor Of MIF On The Tumor Immunosuppressive Microenvironment And The Underlying Mechanism

Background and objective:The morbidity of cancer is increasing year by year,and its mortality is still high,which makes it one of the three major causes of death.One of the main mechanisms for the aggressive tumor growth and metastasis is that cancer cells “educate” the infiltrated immune cells,especially macrophages,rendering their phenotypic change: from tumor-inhibitory M1 phenotype to immunosuppressive and tumor-promoting M2 phenotype.The M2 type of tumor-associated macrophages(TAM)produce arginase-1,which hydrolyzing arginine,resulting in down-regulation of T cell receptor(TCR)and consequently apoptosis of T cells,thereby generating a microenvironment favoring tumor growth and metastasis.Thus,agents able to induce the switch of M2 macrophage to M1 are potentially novel therapeutic approaches against cancer.Previous studies have shown that as a component of tumor-derived exosomes,macrophage migration inhibitory factor(MIF)plays a key role in the phenotypic switch of TAMs to M2 phenotype.While MIF possesses two enzymatic activities,the N-terminal first proline-dependent tautomerase and the cysteine 60-dependent thio-protein oxidoreductase,increasing lines of evidence have indicated that MIF’s tautomerase activity is crucial for its biological functions involved in tumor growth.Through high-through screening,we have successfully identified a small molecular inhibitor of MIF,IMG-122.The purpose of this study was to evaluate the effect of IMG-122 on breast cancer growth and the underlying mechanisms.Methods:1.To establish a screening experiment of drug in vitro that includes the assay on the enzyme activity of MIF,the test of cell proliferation and the binding experiment of CD74-MIF.2.To investigate the effect of IMG-122 on the expression of Arg1 with the technique of co-culture by the exosomes or culture supernatant of tumor cells and macrophage.3.Establishing the animal model of 4T1 breast cancer to investigate whether IMG-122 can inhibit the growth and metastasis of breast cancer,improving the microenvironment and regulating the polarization of TAMs.Results:1.IMG-122 potently inhibited the tautomerase activity of MIF,cancer cell proliferation,and the binding between CD74 and MIF.Therefore,IMG-122 is a candidate drug for further research and discussion.2.IMG-122 effectively inhibited tumor-derived exosome induced polarization of TAMs to M2,resulting in reduced expression of Arg1.3.IMG-122 significantly inhibited tumor growth in a syngeinic breast cancer mouse model.The analysis of the polarization of TAMs showed that IMG-122 could improve the microenvironment of tumor by inhibiting the polarization of TAMs to M2 phenotype macrophage,so as to restore the normal immune function.Conclusions:IMG-122,an inhibitor of MIF,significantly inhibited breast cancer growth.This effect is likely attributable to its inhibitory effects on the immunosuppressive microenvironment.