结直肠癌肿瘤微环境中关键代谢物筛选、鉴定及其对T细胞调控机制研究

T cells are adaptive immune cells with pivotal role in the resistance against tumors. T cells eliminate tumor cells by various mechanisms, including direct killing, secretion of cytokines, and promotion of humoral immune responses. Under physiological conditions, T cells are the most abundant lymphocytes in the intestine, and their functions are regulated by metabolites in the intestinal microenvironment. After colorectal cancer occurrence, a large number of dysfunctional T cells infiltrate into tumor tissues; however, whether the dysfunction of T cells is associated with the disordered metabolites in the local site remains unknown. In this project, tumor tissues and adjacent tumor tissues from patients with clinical stage I — IV colorectal cancer will be used to investigate the dynamic changes of metabolites and T cells in the tumor environment, and to explore the interrelationship between metabolites and T cells with the development of colorectal cancer. Using an in vitro screening system and mouse colon cancer models, we will identify the key metabolite that can affect tumor development by influencing T cell function, and elucidate the mechanism by which the metabolite regulates T cell function. Moreover, the clinical potential of the metabolite will be evaluated by analyzing the correlation between the levels of the metabolite and the prognosis of patients with colorectal cancer. Collectively, this study not only reveals a new pathway for interaction between tumor microenvironment and T cells, but also provides a novel strategy for the development of a combined immunotherapeutic regimen based on targeting metabolites and T cells.

T细胞是机体抵抗肿瘤的核心免疫细胞，可通过直接杀伤、分泌细胞因子以及促进体液免疫应答等多种机制发挥抗肿瘤作用。生理状态下，T细胞是肠道中数量最多的淋巴细胞，其功能受到肠道微环境中代谢物的调控。结直肠癌发生后，肿瘤组织浸润大量功能异常的T细胞，这是否与肿瘤局部代谢物的改变有关尚不清楚。本项目将利用临床Ⅰ — Ⅳ期结直肠癌患者的手术切除标本，通过细胞生物学和代谢组学方法，分析代谢物和T细胞功能状态的动态变化，探究癌变局部代谢物和T细胞在结直肠癌发生发展过程中的内在联系。利用体外筛选体系和小鼠结肠癌模型，鉴定出能够通过改变T细胞功能，进而影响肿瘤进程的关键代谢物，并阐明该代谢物调控T细胞功能的机制。最后分析该代谢物和患者预后的相关性，评估其临床转化价值。此研究不仅揭示肿瘤微环境与T细胞互作的新通路，更能为开发基于靶向代谢物和T细胞的联合免疫治疗方案提供新的策略。

结直肠癌是临床上最常见的消化系恶性肿瘤之一，发病率和死亡率常年居高。CD8+ T细胞是机体抵抗肿瘤的核心免疫细胞，可通过直接杀伤、分泌细胞因子等多种机制发挥抗肿瘤作用。稳态条件下，CD8+ T细胞数量和比例在肠道淋巴细胞中均为最高，其功能受到微环境中代谢物的调控。结直肠癌发生后，肿瘤微环境中CD8+ T细胞功能异常，这是否与肿瘤局部代谢物的改变有关尚不清楚。利用小鼠结直肠癌模型和结直肠癌患者手术切除标本，我们发现CD8+ T细胞的数量和功能随着肿瘤加重而逐渐降低。为寻找通过抑制CD8+ T细胞功能，进而促进肿瘤进程的关键代谢物，我们构建了肠道菌群来源的小分子代谢物库，通过体外筛选，发现代谢物脱氧胆酸（deoxycholic acid，DCA）能够显著抑制CD8+ T细胞效应功能。机制方面，DCA降低CD8+ T细胞胞浆内Ca2+浓度，以及转录因子NFAT活化，从而减少效应分子如IFN-γ、TNF-α 和 Granzyme B的产生。此外，体内实验表明DCA能够促进结直肠癌的发生发展，且其促肿瘤效应是通过抑制CD8+ T细胞功能而实现。为研究其临床转化价值，我们收集了结直肠癌患者粪便，对其进行了质谱检测，并用粪便上清体外刺激CD8+ T细胞，发现含有高浓度DCA的患者粪便对CD8+ T细胞效应功能具有更强的抑制作用。综上，本研究鉴定了一种能够抑制CD8+ T细胞效应功能的代谢物，揭示了肿瘤微环境与CD8+ T细胞互作的新通路，为开发新的免疫治疗策略提供了依据。