T细胞耗竭是制约DC疫苗效应的重要因素。PD-L1是T细胞耗竭的关键性调控点，在肿瘤微环境中持续诱导性表达于肿瘤细胞。然而，目前PD-L1抗体并不能彻底中和这种诱导性表达且部分病人出现耐药。eIF4A是蛋白翻译起始的限速酶，它异常高表达与肿瘤进展及耐药密切相关。我们前期发现：PD-L1表达于黑色素瘤干细胞（MTSCs），并参与MTSCs诱导T细胞耗竭；而eIF4A参与调控MTSCs诱导性高表达PD-L1。由此，我们设想：阻断eIF4A以遏制MTSCs诱导T细胞耗竭而增强疫苗效应。本项目拟从临床水平分析MTSCs中eIF4A和PD-L1的关系及其与肿瘤预后的关系；并从细胞、动物层面研究eIF4A调控MTSCs表达PD-L1在T细胞耗竭中的作用，继而探讨阻断eIF4A在MTSCs-DC疫苗诱导抗肿瘤免疫中的作用及机制，以期为MTSCs诱导T细胞耗竭和MTSCs-DC疫苗联合治疗提供新理论。

Melanoma tumour stem cells (MTSCs)-based DC vaccine significantly inhibited tumor growth and decreased MTSC population in tumor. However, MTSCs-DC vaccine is insufficient to inhibit the progress of melanoma. This finding could be interpreted in several ways, one of the most important causes is persistent antigen stimulation results in T cell exhaustion. Accumulating data pinpoint PD-L as a key immune checkpoint of of T cell exhaustion. The latest theory hold that PD-L1 expression is continued observed on malignant melanocytes.The use of monoclonal antibodies to block immune checkpoints is the biggest therapeutic breakthrough in immunotherapy to date, but a substantial number of patients are resistant to anti-PD-L1 therapy. Regulation of translation plays a crucial role in determining the final levels of proteins in cells, and most regulation occurs at translation initiation. In this process, the eukaryotic initiation factor (eIF) complex eIF4F recruits the small ribosomal subunit to the 5’ end of the mRNA, which is dependent on unwinding of secondary structures by eIF4F’s effector subunit eIF4A.Increased eIF4A activity is a common characteristic of malignancy and related with drug resistance and tumor progression, which has become an attractive target for cancer therapeutics.Our previous study demonstrated that PD-L1 was high expressed in ALDH+MTSCs. Blocking PD-L1 in melanoma cell lines impaired tumorsphere formation and induced the apoptosis of sphere cells. In addition, cytokines enhanced the expression of PD-L1 in ALDH+MTSCs. What’s more, we observed that eIF4A was involved in regulation PD-L1-induced tumorsphere formation. Therefore, we hypothesized that eIF4A- blocking agent can inhibit or reverse MTSCs-intrinsic PD-L1 induced T cell exhaustion. In the present study, we analyze the relationship between MTSCs-intrinsic PD-L1 in patients and the clinical characteristics and prognosis, and confirm the relationship between eIF4A and PD-L1 in MTSCs by PLA. We further study the molecular mechanism of eIF4A regulating the expression of PD-L1 in MTSCs and analyze the role of eIF4A in MTSCs-intrinsic PD-L1 induced T cell exhaustion. We examine the anti-tumor immunity responses of combination blockade of eIF4A and MTSCs-DC vaccine in eIF4A knock out mice. We desire to elucidate combination blockade of eIF4A could reverse the antigen specific T cell exhaustion induced by MTSCs-intrinsic PD-L1 and thereby enhance anti-tumor immunity responses of MTSCs-DC vaccine. If we do that, it will provide a new theoretical and experimental basis for the MTSCs immunology and exploring the adjuvant of cancer stem cell vaccine.