Notch Signaling Regulates Myeloid Cells Differentiation And Maturation By Inhibiting Lactate Metabolism To Impede Tumor Growth

Cancer is the first killer of human health,which attracts most of scientists in the world to study and conquer.The malignant tumor cells are identified with immortalization,metastasis and invasion,resistance to apoptosis,multiple mutation,immune escape and other characteristics,which make major tumors difficult to be cured with surgery alone,radiotherapy and chemotherapy or targeted drugs.Tumor inflammatory microenvironment has become one of the main characteristics of tumors.A large number of immune cells infiltrate into tumor tissues,including tumor associated macrophages(TAMs),tumor associated myeloid(tumor-associated neutrophils,TANs),immature dendritic cells(iDCs),myeloid derived suppressor cells(MDSCs)and regulatory T cells(Tregs).These cells interact with each other to form an immunosuppressive cellular network,which is the key factor to inhibit tumor immunity and promote tumor progression.In tumor microenvironment,myeloid cells play a particularly important role.They could not only directly promote transformation from chronic inflammation to cancer through paracrine pathway,modulate self-renew of cancer stem cell,help the metastasis of tumor cells and promote tumor angiogenesis,but also influence activation of NK cells and cytotoxic T cell to suppress the tumor cells killing.Therefore,how to improve the microenvironment of the tumor,block the immunosuppressive activity of tumor associated myeloid cells and remodel their inflammatory functions,have become crucial directions and strategies for cancer treatment.Compared with the physiological development and differentiation of myeloid cells,tumor associated myeloid cells have the lower degree of differentiation and maturity.There are variance in expression and activation levels of multiple transcription factors and signaling pathways modulating myeloid development and function.Notch signaling,as one of most significant pathway on regulating cells and organs development,plays vital roles in the process of cell proliferation and apoptosis,fate determination and stem cells maintenance.The Notch signal is highly conserved signaling in metazoans.Once the adjacent cell surface ligands and cell surface receptors interaction,Notch intracellular domain(NICD)is released and then translocates to the nuclear to activate target genes transcription by combining with co-activator complex.The role of Notch signaling in myeloid cells is noticeable,but the detailed functions and effect stages are still controversial and the molecular mechanisms remain unclear.On the one hand,Notch signal inhibited myeloid cells to differentiate into mature neutrophils and maintained the undifferentiated or poorly differentiated state through GATAs;at the same time,Notch signal also increased expression of PU.1 to facilitate myeloid cells maturation.It is mainly owing to the different cytokines conditions in different experiments models.Our previous studies suggested that Notch signaling regulated the development and differentiation of myeloid cells via a series of miRNA clusters(unpublished).In addition,the function plasticity of terminal differentiated myeloid cells was also modulated by Notch signaling.Our group has demonstrated that Notch signaling was required for macrophage polarization direction(Wang YC et al,Cancer Res.2010).Later,using liver fibrosis model we found that Notch signal deficient macrophages alleviate hepatic fibrosis through CYLD/NF-?B signaling(He F et al,Hepatology.2015).Recently,our study has verified that the Notch-miR125 a axis could re-educate function of TAM to repress tumor progression(Zhao JL et al,Cancer Res.2016).Taken together,our studies explored that Notch signaling played crucial roles in myeloid cells development and TAM function.In addition to the cell-autonomous regulation,the complicated tumor microenvironment has non-cell-autonomous effect on myeloid development.Tumor cells need amounts of energy and biological materials to support rapid proliferation.Therefore tumor cells utilize glycolysis even in aerobic condition,which is known as Warburg effect and induces nutrients exhaustion and metabolic wastes accumulation.It has been known that alteration of metabolism environment affected phenotype and function of myeloid cells during tumor progression,accompanied with anti-to pro-tumor function conversion.The differently polarized macrophages take advantages of different glucose metabolism ways.M1 type macrophages utilize glycolysis,while M2 type macrophages chose oxidative phosphorylation pathway to supply energy.Besides,it is diversiform in utilization of arginine and lipid in different polarized macrophages.Activation of MDSCs is also modulated by metabolism.Compared with MDSCs in spleen and bone marrow,tumor-associated MDSCs accelerate the uptake and consumption of fatty acids and elevate mitochondrial oxidative phosphorylation level,which is mainly due to lack of glucose in tumor microenvironment.In addition,high concentration of lactate derived by tumor could promote MDSCs accumulation and inhibit cytotoxic activity of NK cells.However,the mechanism remains to be further studied.Based on these findings,the alteration of tumor metabolism in tumor microenvironment is an important signature of cancer progression,which influenced not only tumor cells behavior,but also immune cells function.We wondered whether there was a crosstalk between cell-autonomous regulation and non-cell-autonomous effects on myeloid cells development and function plasticity.Recently,a number of studies have shown that abnormal Notch signaling could lead to functional disorders and abnormal development of metabolic organs.As the main glucose and lipid metabolism organ,the embryo development and regeneration of liver were regulated by Notch signal.Meanwhile,Notch signaling was involved in adipocyte differentiation,as well as the transformation of white and beige adipocytes.In myeloid cells,Notch signal promoted ROS generation by mitochondrial to modulate M1 macrophage function remodeling through metabolism reprogramming.However,the molecular mechanisms on regulation of myeloid cells metabolism trhough Notch signal still needs more detailed studies.In summary,during the process of tumor development,the tumor microenvironment and Notch signal pathway affect myeloid cells differentiation and functional plasticity,and consenquently promote tumor growth.However,little is known about the crosstalk between myeloid cell-autonomous and non-cell-autonomous regulation.Regarding on these problems,our project intend to study the molecular mechanism of Notch signaling in regulating the development and function of tumor associated myeloid cells through metabolic reprogramming.The results and conclusions are shown as follows:1.During the process of tumor development,the immune suppressive G-MDSCs gradually accumulated and the anti-tumor mature M1-liked TAMs reduced;2.The activated Notch signal promoted the differentiation of mature macrophages and inhibited the formation of G-MDSC through regulating of M-MDSC differentiation,leading to tumor growth retardation;3.Notch signaling modulates the differentiation of M-MDSCs and maturation of TAMs through inhibiting the lactate transportion of myeloid cell;4.The lactate could interact with c-Jun,and competitively inhibit combination of c-Jun and FBW7 in the nuclei for blocking its ubiquitination,which could be canceled by Notch signaling activation.In summary,in this study we demonstrated that Notch pathway regulated myeloid cell differentiation by inhibiting lactate intracellular signal exportion and finally suppress tumor growth.Our study also provided new targets and strategies for the establishment of immunotherapy based on tumor associated MDSC and TAM by regulating myeloid cells metabolism,which has important theoretical significance and potential clinical application value.