Mechanism Studies Of L-5-Hydroxytryptophan And Phosphoglycerate Kinase 1 In Modulating Tumor Microenvironment

Tumor microenvironment(TME)is a complicated environment where tumor cells survive,including diverse immune cells,fibroblasts,blood vessels and extracellular matrix.However,tumor cells usually tempt to suppress the immune surveillance functions of immune cells by different mechanisms,leading to immunosuppression and ultimately avoiding the attack from immune system.Activation of immune checkpoint signaling and metabolic reprogramming are two major causes of tumor immunosuppression.Activation of immune checkpoint is mainly reflected in the way that tumor cells induce immune cells to become anergy and inefficient through upregulating the expression of inhibitory receptors in immune cells,and subsequently binding the receptors with related inhibitory ligands on tumor cells’surface.Moreover,ample studies have demonstrated that tumor metabolic reprogramming usually impose metabolic stress on immune cells and thus impair the anti-tumor activity of them,which greatly influences the efficacy of tumor immunotherapy.There are two sections in chapter one.Firstly,the pathophysiological roles of representative immune checkpoints and their implication in clinical are introduced.Secondly,the regulatory mechanisms of tumor glycolysis and the influence of tumor glycolysis on immune cells within TME are demonstrated.Tumor immunity and tumor metabolism have become global hotspot in the field of tumor therapy.Herein,systematically investigating potential strategies modulating immune checkpoint signaling and/or tumor metabolic microenvironment will be helpful to accelerate the understanding of tumorigenesis and tumor progression,which may help to maximize the efficacy of tumor immunotherapy.The first part of this thesis is identifying the mechanism of L-5-hydroxytryptophan(L-5-HTP)promotes antitumor immunity by inhibiting IFN-γ-induced PD-L1expression.In this work,we discover that L-5-HTP suppresses IFN-γ-induced PD-L1expression based on our established screening platform,and this effect is on transcription level.Mechanistically,L-5-HTP inhibits IFN-γ-induced expression of RTK ligands and thus suppresses phosphorylation-mediated activation of RTK receptors and the downstream MEK/ERK/c-JUN signaling cascade,leading to decreased PD-L1 induction.In syngeneic mouse tumor models,intraperitoneally injected with 100 mg/kg L-5-HTP inhibits PD-L1 expression on tumor cells,dendritic cells and macrophages,exhibiting significant and tolerant anti-tumor effect.Moreover,we find an intact immune system and PD-L1 expression on tumor cells is critical for L-5-HTP to exert its antitumor effects,with elevated ratio of granzyme B~+CD8~+activated cytotoxic T cells.Finally,we assess the translational potential of L-5-HTP.L-5-HTP acts synergistically with PD-1 antibody and shows anti-tumor and anti-depression dual effects in chronic social defeat stress-conditioned tumor model.Our findings provide insight into purposing L-5-HTP in tumor immunotherapy.The second part of this thesis is to explore the role of phosphoglycerate kinase 1(PGK1)in modulating triple negative breast cancer(TNBC)cells’proliferation and tumor microenvironment.Through analyzing transcriptome data of TNBC from TCGA database as well as the immunohistochemistry data from TNBC patients’tissues,we found that PGK1 is significantly elevated in TNBC tumor tissues and correlated with TNBC progression.We identify that both genetic intervention and pharmacological inhibition of PGK1 suppress the glycolysis and the proliferation activity of TNBC cell lines in vitro as well as in vivo.Notably,we discover that ablation of PGK1 in vivo reduce the concentration of lactic acid and increase the number of T cells and NK cells within tumor microenvironment.Further investigation on the molecular mechanism of PGK1 mediating tumor microenvironment and tumor metastasis will be performed in the following study.Taken together,we aim to evaluate PGK1 as a potential therapeutic target for TNBC from three aspects including tumor proliferation,tumor microenvironment and tumor metastasis.Overall,based on the two major causes of tumor immunosuppression,this thesis makes use of bioinformatics,molecular biology,cell biology,pharmacology and immunobiology methodologies to investigate novel strategies from mediating PD-L1expression and tumor glycolysis,which builds solid foundation for discovering potential lead compound and new drug target for strengthening the efficacy of tumor immunotherapy.