| Head and neck squamous cell carcinoma(HNSCC)is the sixth most frequent cancer worldwide,characterized by a high recurrence rate,metastasis rate,and low overall survival rate.At present,immunotherapy of HNSCC has brought new hope to people in addition to traditional malignant tumor treatment such as surgery,radiotherapy,and chemotherapy.However,the effectiveness of immunotherapy is severely limited by abnormal metabolites in tumor tissue and the complex immune microenvironment.Research has found that there are a large number of microorganisms and their metabolites(short-chain fatty acids)in the microenvironment of HNSCC,which have important regulatory effects on the immune microenvironment.However,at present,the role of the short-chain fatty acids and their receptors in how immune cells function in the microenvironment in HNSCC remains poorly understood.The regulatory network between them may be involved in mediating tumor immune escape and promoting tumor progression,which needs to be further explored.First,we used bioinformatics to analyze the correlation between short-chain fatty acid receptors and the prognosis of HNSCC.We found that the expression level of GPR43 in tumor tissue was significantly higher than that in normal tissue,and the high expression of GPR43 was positively correlated with the poor prognosis of patients with HNSCC.At the same time,we established subcutaneous tumor models in wild-type mice and Gpr43 gene knockout mice,and found that Gpr43 deletion significantly inhibited the growth of SCC7 transplanted tumors and prolonged the overall survival of the tumor-bearing mice.In addition,to simulate the occurrence and progression of human HNSCC,we used 4-NQO drugs to induce an in situ oral squamous cell carcinoma model,and found that Gpr43 deficient mice do develop fewer and milder scaly aggressive carcinogenesis compared to wild-type mice.Next,we conducted a detailed analysis of the tumor immune microenvironment,and the results showed that the deletion of Gpr43 increased T cell infiltration,particularly significantly increasing infiltration of a subset of IFN-γand Gran B positive T cells.Therefore,through in vivo research,we have identified the role of GPR43 in promoting the occurrence and progression of HNSCC,which also provides clues to the potential functional regulation of GPR43 on T cells.In order to further explore the effects of short-chain fatty acids and their receptors on T cells,we extracted T cells from the spleen of mice to evaluate their proliferation,depletion,and killing levels.We found that GPR43 can significantly inhibit T cell proliferation and reduce the level of IFN-γrelease.GPR43 promotes T cell depletion in a model of prolonged CD3 stimulation-induced depletion,mainly at TIM-3 and PD-1levels.In terms of T cell killing function,the expression of GPR43 can inhibit T cell degranulation.In order to further clarify the effect of GPR43 on CD8~+T cell antigen-specific immune function,we constructed an OT-1 mouse model with Gpr43 deletion,and found that Gpr43 deletion enhanced the cytotoxicity of CD8~+T cells.What’s more,we used GPR43 agonists,acetate,propionate,and butyrate for treatment,and found that these GPR43 agonists and endogenous ligands can inhibit T cell proliferation and killing levels,which further proved the inhibitory effect of GPR43 on T cell function.Therefore,our results suggest that GPR43 may be the key point for HNSCC to avoid T cells.In summary,this study has demonstrated the regulatory role of short-chain fatty acids and their receptor GPR43 on T cells in the immune microenvironment of HNSCC through a series of studies in vivo and in vitro.GPR43 receptor is expected to become a personalized biomarker for immunotherapy,providing new targets and strategies for tumor immunotherapy. |
PDF Full Text Request