Investigation of Gene Candidates as Potential Regulators in the Functional Enhancement of MDSCs by TGF-β

Abstract

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells with a diverse population which is characterized by their immunosuppressive properties in the presence of the soluble mediators released from tumor microenvironment or in an inflammatory environment. MDSCs are classified into two distinct subsets based on their surface marker expression: CD11b+Ly6C+Ly6G- monocytic MDSCs (Mo-MDSCs) and CD11b+Ly6Cint/loLy6G+ granulocytic (or polymorphonuclear) MDSCs (Gr-MDSCs). It has been proven previously that TGF-β enhances the immunosuppressive function of MDSCs. To identify the gene candidates involving in the TGF-β-mediated functional enhancement of MDSCs, Elovl3 was selected from the gene candidates based on the change of its gene expression showed by previously performed microarray analysis. After selection of the gene candidate, recombinant Elovl3 was built and retrovirus packaging cells were transfected by the recombinant Elovl3. This retroviral system was further used to infect MDSCs during their in vitro differentiation from bone marrow cells isolated from with and without TGF-β. After creating the overexpression system of the Elovl3 in MDSCs, the relative expression of iNOS as an immunosuppressive molecule produced by Mo-MDSCs was tested by performing qPCR analysis to analyze MDSCs functionally. Based on the performed qPCR analysis, overexpression of Elovl3 in MDSCs induced MDSCs to have a decreased iNOS expression. However, the fold change in iNOS expression was significantly increased by the TGF-β treatment. Thus, Elovl3 may be a potential regulatory gene in the TGF-β-mediated functional enhancement of MDSCs and its expression might be altered in metabolically reprogrammed MDSCs in the functional enhancement by TGF-β