IL-24修饰的益生菌双歧杆菌抑制头颈部鳞状细胞癌的分子机制研究

Bifidobacterium, as its low immunogenicity, well targeting and certain immune regulation ability, has become a promising vector for cancer treatment. Bifidobacterium can be used to regulate the immune ability to achieve anti-tumor effect, but the molecular mechanism is still to be perfected. Its anti-tumor effect remains to be improved and the body distribution in oral administration is still controversial.In our previous work, Interleukin-24 transformed Bifidobacterium strain B.breve-IL24 was constructed. It could target the tumor well and its anti-tumor effect was better than the wild type B.breve. Based on this, we intend to make a further exploration on the molecular mechanism of oral administration of B.breve-IL24 in inhibiting cancer, following the methods as below. Firstly, head and neck squamous cell carcinoma cell line was used to construct the tumor-bearing animal model under different immune conditions, and the tumor size was detected to verify the anti-tumor effect. Secondly, the function of immune cells in circulation and tumor tissue, as well as the apoptosis of tumor cells were identified. Thirdly, by analyzing the intestinal microbiome and exploring the effect of B.breve-IL24 on dendritic cells, intestinal epithelial cells and squamous cell, the molecular mechanism of inducing apoptosis and enhancing anti-tumor immunity was clarified. By constructing a strain of Bifidobacterium breve expressing far-infrared protein mKate2, we could monitor its distribution in real time in vivo. Based on the above, we hope to provide a practical basis for the use of Bifidobacterium as a vector for cancer immunotherapy.

双歧杆菌是肿瘤研究领域极具前景的治疗载体，其免疫原性低，靶向性高，具有一定的免疫调节能力，但其抗肿瘤的分子机制尚不完全明确，抗肿瘤效果仍有待提高,且口服后的体内分布尚存争议。课题组前期构建了白细胞介素-24（IL-24）修饰的短双歧杆菌菌株B.breve-IL24，并证实经尾静脉注射后其具有明显的肿瘤靶向性且抑癌作用强于野生株。为进一步探究口服B.breve-IL24的抑癌作用及分子机制，本项目拟从以下三方面开展：①构建头颈鳞癌荷瘤动物模型，验证口服B.breve-IL24的抑癌作用。②检测口服B.breve-IL24后肿瘤组织的凋亡情况，以及全身和肿瘤微环境中免疫功能的变化。③分析肠道菌群以及双歧杆菌自身对树突状细胞、肠上皮细胞及鳞癌细胞的作用，明确抗肿瘤作用机制；并通过转化远红外蛋白mKate2，实时监测其体内分布。本研究将为双歧杆菌作为肿瘤免疫治疗载体运用于临床提供切实理论依据。

双歧杆菌在我们的日常饮食中并不少见，如酸奶。近两年来新冠病毒全球大流行，人们更加看重对全身免疫力的提高，表现出益生菌相关的产品与日俱增，益生菌市场规模逐年扩增。本项目出发于经IL-24修饰的短双岐杆菌尾静脉注射后靶向抗肿瘤作用，发现其可促进肿瘤细胞的凋亡。而后口服B.breve-IL24的抑瘤作用也很显著。那口服益生菌对于全身免疫调节如何发挥作用以及在抗肿瘤方面的作用如何是成为本项目回答的第二个内容。我们发现口服双歧杆菌可以通过调节肠道局部免疫微环境，活化并募集CD11b-CD103+DC细胞分泌IL-12发挥远端抗肿瘤作用。IL-12在其中发挥决定性作用。该菌对于肠道菌群的调节在其抗肿瘤免疫中也不可忽视。本项目在申请书基础上做深度拓展，探究双歧杆菌的代谢产物之一——胞外多糖，在其发挥抗肿瘤免疫中的作用。新分离的双歧杆菌菌株B.breve lw01经基因组比对及生物合成路径分析，明确其EPS合成过程，且可抑制肿瘤细胞生长。针对胞外多糖的作用研究及结构解析开发，将为精准开发双歧杆菌的有效成分提供基础工作。