The Mechanism By Which PCB Regulates TAMs Functions To Reprogram Tumor Microenvironment

Macrophages are suffered from hypoxia and nutrients competition in the tumor microenvironment.The shortage of nutrients and oxygen at the same time will disrupt metabolic homeostasis of macrophages,and change the patterns of macrophage activation and polarization.Therefore,the metabolism,phenotype and function of macrophages are reprogrammed in the tumor microenvironment,which in turn mediate the crosstalk between macrophages and tumor cells,and affect tumor progression and prognosis.Gluconeogenesis is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates,such as lactate.In response to nutrients shortage,cells,especially hepatocytes,undergo gluconeogenesis to maintain the supply of substrates and energy.Some tumor cells have been proven to take advantage of gluconeogenesis to support their rapid proliferation and survival.However,the functions of gluconeogenesis and its' key enzymes in immune cells have not been completely elucidated.Besides,thorough and extensive study is still needed to determine whether gluconeogenic enzymes have moonlighting functions.In our preliminary study,we found that the gluconeogenic pathway was changed in TAMs of several tumors.Based on this observation,we carried out in-depth study and found that:(1)The expression and regulatory mode of the key gluconeogenic enzyme PCB in TAMs were changed: Our study found that the abundance and activity of PCB in TAMs were repressed by hypoxia in the tumor microenvironment.The downregulation of PCB impaired TAMs phagocytosis and endowed TAMs with T-cell inhibitory property,which in turn promoted the formation of immunosuppressive microenvironment.(2)PCB regulates TAMs phagocytosis in an activity-independent manner: We found that PCB could translocate from the mitochondria to the cytosol,and interacted with MYH6 at the pseudopodia,which indicated that the cytoskeleton may be reporgrammed.Further study showed that the downregulation of PCB in TAMs relieved the inhibition of MYH6,which inhibited the phagocytosis of tumor cells by TAMs.(3)PCB controls the T-cell inhibitory activity of TAMs in an activitydependent manner: The T-cell inhibitory activity of TAMs was under control of PCB enzymatic activity.The downregulation of PCB activity led to the upregulaiton of PD-L1 on TAMS,which mediated the inhibitory effect of TAMs on T cells activation and proliferation(4)The construction and evaluation of oxygenation + activation bifunctional nanoparticles: According to the regulatory pattern of PCB expression,we used FDC@HSA to oxygenate the B16 tumor in vivo and found that the PCB expression and phagocytosis of TAMs were significantly enhanced,while PDL1 of TAMs was decreased by delivering oxygen to the tumor.In consistent,oxygenation of the tumor reprogrammed the immune microenvironment,strengthened the anti-tumor immunity and delayed tumor growth.To enhance the anti-tumor effect of FDC@HSA nanoparticle,we designed a bi-functional nanoparticle named FDC-GTA@HSA,which could induce PCB expression by oxygenating the tumor and activate PCB by elevating the content of acetyl-Co A at the same time.Compared with FDC@HSA,FDC-GTA@HSA was more potent in promoting anti-tumor immunity and stunting tumor growth.Collectively,we found that the key gluconeogenic enzyme PCB regulated the phagocytosis and T-cell inhibitory activity of TAMs in an activity-independent and-dependent manner respectively,which in turn reprogrammed the immune microenvironment.The hypoxia in the tumor microenvironment contributed to the repression of PCB.Accordingly,we designed a new bi-functional nanoparticle named FDC-GTA@HSA,which could enhance anti-tumor immunity and stunted tumor growth significantly by relieving tumor hypoxia and intervening the expression and activity of PCB.The success of FDC-GTA@HSA in inhibiting tumor growth also confirmed the results of our study.