IL-1β Secreted From Lactate-primed Macrophages Boosts The Expression Of PD-L1 To Reshape The Immunesuppressive Microenvironment

Objective:Cytokines such as interleukin superfamily,chemokines and others massively flooded in the tumor microenvironment and extensively participate in the processes of information transmission between cells.However,how these cytokines participate in tumor immune escape are still elusive.The main purpose of this study is to thoroughly explore the key cytokines and the mechanisms that lead to the remodeling of the tumor immune microenvironment.Further,to define whether the cytokines can be seemed as robust target to activate the immune system and reverse the tumor immunosuppressive state of microenvironment,improve the prognosis of cancer patients.Methods:Human ovarian cancer cell line SKOV3 was co-cultured with the human monocyte cell line THP1,and then the cytokine array was used to detect the changes in cytokine secretion in the microenvironment after the crosstalk between the above tumor cells and THP1.We selected cytokines with significant change as potential target and used clinical sample to analyze the possible relationship between them with the prognosis of cancer patients.In vitro and in vivo experiments were carried out to clarify the role of this target on tumor immune escape.Clinical samples and database information were further used to verify its promotion of tumor immune escape phenotype.Results:A variety of cytokines including IL-1β、MIP-1α(CCL3)、MPIF-2、TCA-3(CCL1)、TNF-RII、CXCL13、MIP-1δ(CCL15)、G-CSF and so on,showed increased secretion after co-culture were screened out and IL-1βpossessed the strongest effect to induce PD-L1 expression of tumor cell through RNA-seq detection and analysis after derictly stimulation of all these cytokines.Analysis of clinical samples showed the correlated relationship of IL-1βsecretion with the amount of Granzyme B~+T lymphocyte infiltration and patient prognosis.Further in vitro experiments confirmed that IL-1βcould act as a mediator of interaction between tumor-associated macrophage and tumor cell to induce immune suppression.At the mechanism level,we found that tumor-associated macrophage activated NF-κB signaling pathway of tumor cell by secreting IL-1βto induce the PD-L1 and CCL2 expression.Conversely,secretion of lactate by tumor cell promoted the synthesis and secretion of IL-1βby macrophage.Furthermore,IL-1βneutralizing antibody treatment on tumor-bearing mice significantly restrained tumor growth and the therapeutic effect was significantly enhanced once combined with anti-PD-1 antibody.Conclusions:Our results proved that tumor-associated macrophage and tumor cell were involved a vicious cycle that resulting in tumor immune escape through the secretion of IL-1βand lactate for the first time.IL-1βas a regulatory factor can not only directly inhibit the function of CD8~+T cell,but also recruit immunosuppressive cell components including macrophage into the microenvironment.Therefore,IL-1βcan be used as a powerful therapeutic target in the treatment of tumors,and its combination with PD-1 neutralizing antibody can significantly enhance the therapeutic effect on solid tumors.In addition,our study proved the important role of cytokines in the tumor microenvironment and provided pivotal clues for the direction of finding new targets for tumor therapy.