Study On The Regulatory Mechanism Of Chidamide On PD-1/PD-L1 Immune Escape Signaling Pathway In Peripheral T-cell Lymphoma

Background and ObjectivesPeripheral T-cell lymphoma(PTCL)is a group of highly heterogeneous non-Hodgkin lymphoma originated from mature T cells.The incidence rate in China is obviously higher than western countries.The prognosis of T-cell lymphoma is significantly worse than B-cell lymphoma.The standard chemotherapy regimen is effective,but there are some problems such as short remission time and high recurrence rate.Therefore,further study on the pathogenesis of PTCL is of great significance to find new treatment methods and improve the prognosis of patients with PTCL.In clinical,PD-1/PD-L1 monoclonal antibody has a certain effect on tumor treatment,but there are low response rate and recurrence after effective treatment.At present,there are few clinical studies of PD-1/PD-L1 monoclonal antibody in the treatment of PTCL.Therefore,it is of great clinical significance to explore how to inhibit tumor immune escape mediated by PD-1/PD-L1 pathway.Chidamide,an HDAC inhibitor,regulates the antitumor effect of host immune system by epigenetic modification,which has certain effect on tumor,especially hematological malignancies.In clinical,Chidamide and PD-1 monoclonal antibody have synergistic effect on the treatment of lymphoma,suggesting that Chidamide may play a role in regulating the signaling pathway of PD-1/PD-L1 immune escape.From the perspective of epigenetics and immune checkpoint combination,this study aims to explore the regulatory mechanism of Chidamide on PD-1/PD-L1 immune escape and to provide a new theoretical basis for future clinical treatment.MethodsJurkat cells were treated with different concentrations of Chidamide.The mRNA expression levels of PD-L1,JAK/STAT pathway genes and chemokines CXCL3 and CXCL9 were detected by fluorescence quantitative PCR.Cell surface PD-L1 protein expression was detected by flow cytometry.Lymphocytes were extracted from human peripheral blood and stimulated to proliferate in vitro.Lymphocytes treated with Chidamide alone and lymphocytes co-cultured with Chidamide treated Jurkat cells were set.The RNA expression levels of CXCL3 and CXCL9 in lymphocytes of each group were detected by fluorescence quantitative PCR.The proportion of CD8+T cells was detected by flow cytometry.Results1.Chidamide upregulated PD-L1 mRNA expression in Jurkat cell line in a dose-dependent manner.2.The proportion of PD-L1 positive cells in Jurkat cell line was low.Low dose of Chidamide(0.5-1?mol/L)increased the proportion of PD-L1 positive cells in Jurkat cell line,but high dose of Chidamide(2-5?mol/L)did not.3.Chidamide upregulated the average level of PD-L1 protein on Jurkat cell surface.The effects of different doses were similar.4.Chidamide upregulated the RNA expression of JAK2,STAT1 and STAT3 in Jurkat cell line.The level of up-regulation was obvious in high concentration group(5?mol/L group).At the same time,the mRNA expression of SOCS1 and SOCS3,the negative regulatory genes upstream of the JAK/STAT pathway,were up-regulated.5.In Jurkat cell line,Chidamide may enhance the efficacy of PD-1 monoclonal antibody by upregulating STAT1 and T cell chemokines.6.Chidamide upregulated CXCL9 RNA expression in Jurkat cell line in a dose-dependent manner,which may enhance the efficacy of PD-1 monoclonal antibody.7.Chidamide upregulated CXCL9 mRNA expression in lymphocytes.The up-regulated level was significantly lower than that in Jurkat cell line treated with the same concentration of Chidamide.8.Co-culture with Chidamide treated Jurkat cells upregulated the proportion of CD8+T cells in lymphocytes.The possible mechanism is that Chidamide can upregulate CXCL9 expression by upregulating STAT1 expression of Jurkat cells,leading to the increase of the CXCL9 concentration and the number of CD8+T cells in the environment.ConclusionPossible mechanisms of how Chidamide regulates PD-1/PD-L1 immune escape:1.Chidamide upregulates the RNA expression of PD-L1 in Jurkat cells and increases the action target of PD-1 monoclonal antibody.2.In Jurkat cell line,Chidamide upregulates CXCL9 through STAT1,increasing the CXCL9 concentration and the number of CD8+T cells in the environment,overcoming immune escape and playing a synergistic role with PD-1 monoclonal antibody.