LeX检查点通过DC-SIGN信号轴介导T细胞抑制和肿瘤浸润促进白血病免疫逃逸的机制研究

在总结前人与自身工作基础上，我们假设：白血病细胞通过建立circZCCHC2-miR22/miR23a-FUT4-LeX-DC-SIGN信号轴抑制了机体免疫防御反应；LeX可作为白血病免疫检查点，阻断LeX介导的肿瘤-树突细胞识别能够促进T细胞活化、抑制白血病细胞浸润。取初诊和复发白血病患者骨髓样本进行转录组测序，结合生物信息学分析和基础实验验证，证实circZCCHC2调控LeX合成的机制。为了阐述LeX对白血病免疫的影响，我们将利用涉及免疫学、糖生物学、遗传学和生物信息学的研究方法，结合糖工程抗体制备、细胞表面糖链检测、糖基化相关基因敲除、体外细胞共培养、PDX模型和同源小鼠模型构建等实验技术探讨LeX对T细胞功能和白血病细胞浸润能力的影响，并在多种细胞模型和小鼠模型中，观察利用LeX抗体或FUT4基因敲除的方法重新激活T细胞攻击白血病细胞的能力，该研究有望为白血病带来新的免疫疗法。

Leukemia employed unique immune evasion mechanisms distinct from human solid cancers and other hematological malignancies such as lymphoma, but the precise cause remains unclear. LeX can be considered as a novel type of immune checkpoint for its utmost importance in determining the subsequent skewing toward immunity or tolerance. By expressing a large amount of LeX in the cell surface, pathogens and cancer cells disguise themselves and hijack the immune system for their own benefit. LeX can intrigue the DC-SIGN immune-suppressive pathway and the secretion of suppressive immune molecules, prevent the maturation of dendritic cell, disturb the antigen-presenting procession, shift the differentiation balance towards Th2 cell, and eventually weaken the host anti-tumor effect. Exaggerated expression of LeX was also discovered in leukemia cells and contributed to a deleterious outcome. Deciphering how LeX dictates immune-suppressive circuits in the tumor microenvironment contributes to the potential use of the glyco-code in the development of new diagnostic and therapeutic strategies. .Our previous study has disclosed that fucosyltransferase FUT4 was the key enzyme that catalyzed LeX synthesis in leukemia. To elucidate how FUT4 was up-regulated, RNA sequencing, bioinformatics analysis and experimental validation were applied to screen out circZCCHC2-miR22/miR23a-FUT4 axis. In this project, interdisciplinary approaches that bridge immunology, glycobiology, genetics, and bioinformatics together with innovative technologies including glycan arrays, bioengineering of cell-surface glycans, glycan visualization in vivo, tissue specific deletion of glycosylation-related genes, performing human leukemia xenograft (PDX) and mouse leukemia allograft will be conducted to validate this regulatory axis existence and the effect of LeX on leukemia immune response and infiltration. Whether LeX checkpoint blockade via FUT4 knock down or antibody will reactivate T cell function and resume infiltration inhibition or not was also mentioned for therapeutic purposes. .In summary, a hypothesis was posed that LeX, a tumor-associated glycan and an adhesion molecule, supports tumor cell infiltration into tissues and suppresses T cell activity via circZCCHC2-miR22/miR23a-FUT4-LeX-DC-SIGN signaling axis in acute lymphoblastic leukemia (ALL) cells. Blocking LeX signaling using knockout and antagonistic antibody approaches impeded ALL development. Thus, LeX orchestrates tumor invasion pathways in lymphoblastic leukemia cells by creating an immune-suppressive microenvironment. LeX represents a compelling target for treatment of ALL.