In present study, we demonstrated that the percentage of CD4+ T cells decreased in LN + compared to LN-. We also found that expression of PD1 and glycolysis related enzymes elevated in CD4+ T cells from metastatic lymph nodes. These results indicated that increased PD1 of CD4+ T cells in LN + facilitates the lymph node metastasis progression via glucose metabolism and aerobic glycolysis fuel. In following experiments, the findings revealed that PD1 and Hk2 of CD4+ T cells were upregulated in P-LN + compared with N-LN+.
T cells inhibit tumor cells in various ways, either directly by killing tumor cells via cytolytic mechanisms or indirectly by modulating the tumor microenvironment. Emerging evidences revealed that CD4+ T cells is necessary to initiate and maintain anticancer immune responses[18, 19]. Furthermore, CD4+ T cells could increase the quality and magnitude of B cell and CD8+ cytotoxic T lymphocytes responses in lymph nodes. Our findings suggested that the decreased percentage of CD4+ T cells in LN + inhibit anti-tumor immunity, which contribute to progression of OSCC metastatic lymph nodes. The previous study showed that the OSCC patients with elevated CD4+ T cells had a poorer prognosis. This difference may attribute to different cell types between lymph node and primary tumor. Lymph nodes include various immune cells and primary tumor composed mostly of tumor cell. Metastatic lymph nodes contain tumor cells and immune cells, while the percent of immune cells decreased correspondingly.
A previous study in cervical carcinomas reported that PD1 was expressed by a vast number of infiltrating CD8+ T cells, suggesting that PD1 could serve as a potential therapeutic target. In additionally, recent study suggested that CD4+ T cells as pivotal regulators of PDL1 levels, determined the immune responsiveness to PD1-based immune checkpoint therapy in OSCC patients. The present study found that the increased PD1 expression of CD4+ T cells in LN + could promote lymph nodes metastasis, suggesting that blocking of PD1 could have therapeutic potential in OSCC patients. Chronic antigen exposure, such as occurs with cancer, can lead to upregulated PD1 expression levels, which induces a state of anergy or exhaustion among cognate antigen-specific T cells.
T cells do not have enough internal glycogen stores, making them highly dependent on uptake of extracellular glucose to meet increased metabolic needs during an immune response. If T cells fail to meet increase glucose metabolic needs due to direct metabolic inhibition or inadequate nutrients, T cells proliferation and activation are suppressed. Moreover, the immune checkpoint PD1 associated with T cell metabolism. The study of Bengsch have shown that PD1 regulates glycolysis, metabolism and mitochondrial function of virus-specific CD8+ T cells in chronic lymphocytic choriomeningitis virus infection. Our results demonstrated that increased PD1 of CD4+ T cells in LN + was associated with glycolysis related enzymes, indicating that increased PD1 of CD4+ T cells inhibit anti-tumor immunity via glucose metabolism and aerobic glycolysis fuel. Furthermore, we also found that PD1 and Hk2 of CD4+ T cells were increased in P-LN + compared to N-LN+, suggesting that Hk2 is a key enzyme in glycolysis, contributing to progression of metastatic lymph nodes in OSCC.