Inhibition Of EGCG On Tumor Immune Escape By Regulating MDSCs-mediated Immunosuppression

The potential prevention of EGCG on cancers,including prostate cancer,breast cancer,and lung cancer,etc.,has been suggested by in vitro and in vivo studies.However,the effective concentrations of EGCG on cancers are hardly reached in vivo due to its low bioavailability,leading to the mechanism of its anticancer effect is still unclear.As known,tumors are closely related to immunity.The antitumor immune response of host could be blocked by tumors,which called tumor immune escape,and its mechanism is very complex.Myeloid-derived suppressor cells(MDSCs)as main cells in body that down-regulating the antitumor immune response have been considered as a critical factor in tumor immune escape.However,to date,there are few ettention paid on the role of MDSCs invovled in the antitumor effect of EGCGIn the present work,the inhibition of EGCG on breast cancer(4T1 cells)was evaluated both in vitro and in vivo.Meanwhile,the modulation of EGCG on CD11b~+Gr-1~+MDSC and key factors related immune state,such as CD4~+T,CD8~+T,Treg,Arg-1 and iNOS was explored.After that,MDSCs were purified from spleen of breast cancer mice induced by 4T1,and the regulation of EGCG on MDSCs and critical factors involved in immunosupression mediated by MDSCs was investaigted further.The obtained results are presented as below:1.EGCG was found to change the morphology markedly,and does-dependently inhibited proliferation of 4T1 cells in vitro.And purity of EGCG positively affected its activity,higher purity was observed with stronger acitivty.Besides,the migration and invasion of 4T1 cells was attenulated by EGCG in the testd concentrations.However,the capacity of induced apoptosis on 4T1 cells was not remarkable,the apoptosis rate was 12.5%after treatment of EGCG at a concentration of 250?g/ml.2.In vivo model,it was shown that EGCG could inhibit growth of tumor and swelling of spleen,and reduce the content of CDllb~+Gr-1~+MDSCs in blood,spleen and tumor tissue in mice,which indicated the EGCG could attenuate the immunosuppression in mice body.Meanwhile,EGCG was able to inhibit tumor immune escape by decreasing the expression of Treg,Arg-1 and iNOS,and increasing the contents of CD4~+T and CD8~+T in breast-bearing mice.3.Regarding the modulation of EGCG on MDSCs in vitro.EGCG could directly reduce the immunosippression ability ofMDSCs by reducing apoptosis and retarding cell cycle.Meanwhile,it was able to down-regulating the exgression of Arg-1,iNOS,gp91 and p47,and then to decrease the content of Arg-1 and ROS,which could enhance the activation and proliferation of T cells.Furthermore,the activation of MDSCs could be inhibited by EGCG via reducing expression of GM-CSF,IL-6,IL-13.And EGCG was able to reduce the expression of TGF-??IL-10,which indicated recruitment of Treg and transformation to the M2 phenotype of macrophage would be limited,and that could increase the activity of T cells,4.By comparing the effective concentration of EGCG on 4T1 cells and that on MDSCs,it was found that MDSCs were more sensitive to EGCG than 4T1 cells.As shown,the apoptosis rate of MDSCs rised from 6.8%(control)to 10.7%(0.5?g/ml EGCG),and the apoptosis rate of 4T1 cells,treated with EGCG at a concerntration of 50?g/ml,was only 2.8%.