The Study On Tumor Immunotherapy Based On The Function Of The Key Immune Cells In Tumor Microenvironment

Cancer immunotherapy is to harness the power of the patient's own immune system to reject cancer,and has become a hotspot in the field of tumor treatment.The anti-tumor effect of the body is mainly T cell(CD8+ cytotoxic T cells and CD4+ type 1 T helper cells)-mediated the adaptive immune response.However,the tumor microenvironment which could promote tumor growth,and low immunogenic in tumor itself,which lead to exist the activation barrier of CD8+ cytotoxic T cells and CD4+ type 1 T helper cells in the patient or the functions of both cells to be suppressed in the tumor microenvironment,all of these has become the main obstacle to the immunotherapy.Therefore,to explore and illustrate the regulatory mechanism of CD8+ cytotoxic T cells and CD4+ type 1 T helper cells has very important value on the study of tumor immunotherapy.Meanwhile,tumor microenvironment exist the infiltration of immunosuppressive cells such as myeloid derived suppressor cell,tumor associated macrophage and Treg,and in line with the characteristics of these cells,to design and screen some macromolecular polymers and small molecular compounds to re-polarize or inhibit these cells to awaken the patient's own anti-tumor immune effect to reject tumor,which might provide a new way for tumor immunotherapy.First,we used miR-21-deficient mice to test the effect of the allograft tumor growth.By developing two distinct allograft subcutaneous tumor models(S180 and Heps tumor models)in miR-21 KO mice,we found that miR-21 deficiency in host mice dramatically enhanced the growth of the grafted tumors by dampening the anti-tumor immune reactions of the body.Next,we transferred a mixture of WT CD4+and CD8+ T cells into miR-21-/-mice and found that miR-21-/-mice receiving the mixture partly restored their anti-tumor response,which suggested that the pro-tumor effect in miR-21-/-mice was indeed due to a T cell deficiency.In normal condition(without immune stimulation),miR-21 deficiency did not lead to apparent global immune abnormalities in miR-21-/-mice.Once with immune stimulation,miR-21 deletion could inhibit the proliferation and function of T cell but not affect the apoptosis of CD4+ T cells and CD8+ T cells in vivo and in vitro.We sought to determine the mechanism by which miR-21 regulates CD4+ and CD8+ T cells'responses to stimulation,and found miR-21 mediated the response of CD4+T cells and CD8+T cells to stimulation via PTEN/Akt signal pathway.Lastly,overexpressing miR-21 or knock down PTEN expression in miR-21-/-CD4+ and CD8+ T cells would restore CD4+ and CD8+T cell response.Therefore,our results uncover that miR-21-/-mice lead to a T cell deficiency to cause damage the anti-tumor immune reactions of the body and accelerate allograft tumor growth,and the mechanism by which miR-21 regulates CD4+ and CD8+ T cells' responses,which provide an important research direction for adoptive immune cell therapy.Meanwhile,combining with emerging reports establishing a crucial role for miR-21 in tumor promotion,miR-21 is a dynamic,bi-directional regulation of this microRNA over tumorigenesis.Some macromolecular polymers such as cationic polymers have also the effect of immune activation and could cause the body's immune response.Our previous studies reported that two cationic polymers,namely cationic dextran(C-dextran)and polyethyleneimine(PEI),are ligand of TLR-4.MDSCs are important immunosuppressive cells in tumor microenvironment,and could effectively restrain anti-tumor immune effect of T cells to promote the tumor growth,so they seriously hinder the effect of tumor immunotherapy.Several studies have demonstrated that modulation of the toll-like receptors(TLRs)signaling in MDSCs could re-activate immunosurveillance against tumor and thereby enhance immunotherapy.Therefore,we hypothesized that cationic polymers could re-polarize MDSCs via TLR4 signaling,consequently triggering desired immune responses and restoring cancer immunosurveillance.We demonstrated firstly that cationic materials could program the phenotypic polarization of MDSCs and inhibit their suppressive function in a TLR-4 dependent manner.Next,we examined whether these would affect tumour growth in 4T1 tumor model.The results demonstrated that cationic materials could re-polarize MDSCs towards M 1-type in vivo,decrease MDSCs number in the blood,spleen,tumor and even bone marrow(BM),restore the proliferation and functions of CD4+ and CD8+ T cells,retard the tumor growth and prolong survival period-Lastly,we demonstrated that TLR-4 signaling is required for the anti-tumour activity of cationic polymers.Therefore,cationic polymers have a very good anti-tumor effect,which provides a solid theoretical basis for its clinical application.Besides MDSCs,there are also two immunosuppressive cells in tumor microenvironment:tumor associated macrophage(TAM)and regulatory T cells(Treg),and both cells could inhibit the body's anti-tumor immunity to promote tumor growth.Several studies have demonstrated that STAT3 in TAM and Treg in tumor microenvironment are continuous activation.Meanwhile,the Jak2-STAT3 signaling could polarize macrophage towards M2-type,and promote the generation and function of Treg cells.Therefore,to design and select some small molecule compounds which could inhibit Jak2-STAT3 signaling to re-polarize the phenotype of TAM and inhibit the generation and function of Treg is an application prospect of the new strategy for tumor immunotherapy.First,we selected a small molecule inhibitor of Jak2 kinase,small molecule compounds 21,and further evaluate that it could promote macrophages toward M1-type macrophage,and also could re-polarize TAM phenotype.At the same time,it could also inhibit the generation and function of Treg cells.Next,we used three kinds of tumor models to explore the anti-tumor effect of compound 21.The data demonstrated that compound 21 could also re-polarize TAM phenotype and inhibit the generation and function of Treg cells in vivo,restore the proliferation and functions of T cells and inhibit tumor angiogenesis so as to realize the feasibility of anti-tumor,which proves that compound 21 is a very promising anti-tumor immune therapy drug candidates.