Roles Of Elevating The Expression Of MHC Class Ⅰ And Ⅱ Molecules On Tumor Cell Surface In Tumor Immunogenicity

Background: Tumor immunotherapy has made great progress in recent years and has become one of the most compelling directions in tumor therapy.The major histocompatibility antigen complex(MHC)is primarily responsible for the presentation of antigens and is an important component of the immune system of the organism.MHC class I molecules bind to endogenous antigenic peptides derived from cells and can be recognized by binding to CD8 cells while MHC class Ⅱ molecules bind to exogenous antigenic peptides and bind to CD4 T cells to be recognized.The expression of MHC class Ⅱ molecules on tumor cells is associated with survival and response to immunotherapy.However,the expression of MHC Ⅱ molecules on the surface of tumors and the mechanisms behind immunotherapy are still unclear.Epitopes that bind to MHC class I and class Ⅱ molecules are referred to as CD8 and CD4 T cell epitopes,respectively.The binding of an epitope to an MHC molecule is an important step in the antigen presentation process,and the epitope is highly selective and sensitive in the process of binding to the MHC molecule.Tumor cells can not be effectively presented to CD8 T cells by reducing the expression of MHC I on their surface,so CD8 T cells cannot exert the ability to kill tumors.The relationship between the expression of MHC class I and Ⅱ molecules on the surface of tumor cells and tumor immunogenicity has not received sufficient attention.At present,promoting the activation of T cells by various means is one of the highlights in the field of tumor immunotherapy.This study focuses on elevating the expression of MHC class I and Ⅱ on the surface of tumors,enabling tumor antigens to be efficiently presented to T cells to activate anti-tumor immunity.Objective: Elevating the expression of MHC II molecules or MHC I molecules on the surface of tumor cells or both,so that tumor cell surface antigens can be efficiently presented to CD4 T cells and can be recognized by CD8 T cells,thereby activating anti-tumor immune responses efficiently.It provides new ideas for related tumor cell vaccines and anti-tumor treatment research.Methods: 1.Gene vector containing mouse H-2Dd molecule was constructed and transfected into B16 melanoma cells to obtain an B16 cell line stably expressing mouse H-2Dd molecule.2.Different numbers of constructed B16 cells stably expressing mouse H-2Dd were inoculated subcutaneously into C57BL/6 mice after irradiation with radiation,and after a certain time,wild type B16 cells were subcutaneously inoculated to construct a mouse melanoma model.Body weight and tumor volume were measured.3.Different concentrations of TSA(histone deacetylase inhibitor,HDACI),azacitidine(DNA methyltransferase inhibitor)and IFNγ were used to stimulate the expression of MHC I and MHC II on B16 cells.B16 cells expressing MHC I and MHC II were inoculated subcutaneously after irradiation with radiation.A mouse model of melanoma was constructed by subcutaneous inoculation of wild-type B16 cells.Body weight and tumor volume of the mice were measured.The ratio of various immune cells in lymph nodes and tumor tissues was detected by flow cytometry.The distribution of various immune cells in tumor tissues was used to detect by Immunohistochemistry.Results:1.B16 cells stably expressing mouse H-2Dd molecules were constructed.2.Compared with the group of wild type B16 cell,the B16 cell stably expressing the mouse H-2Dd molecule could not effectively activate the anti-tumor immune response.3.The expression of MHC I and MHC II on B16 cells was up-regulated by azacitidine combined with IFN-γ stimulation.4.Azacitidine combined with IFN-γ-stimulated B16 cells can effectively activate the anti-tumor immune response,and the expression of CD4 T cells in tumor tissues was elevated.Conclusion: Application of azacitidine combined with IFNγ stimulated the expression of MHC class I and II molecules on the surface of tumor cells,promoted the presentation of tumor antigens in mouse melanoma cells,activated the anti-tumor immune response of mice effectively,while elevating the expression of heterologous MHC class I molecules on the surface of tumor cells does not enhance the immunogenicity of mouse melanoma cells.