细菌在肿瘤治疗中对瘤内谷氨酰胺代谢的干预机制研究

Bacterial tumor therapy is one of the most topical treatments, because the tumor will be suppressed by bacterial toxicity or immune system activated by bacteria. In our previous study, we had confirmed that Salmonella can specifically target tumours, and bladder carcinoma cells (MB49) were negative growth in the culture medium with low concentration of glutamine, implying that the solid tumors could be suppressed by disorganized glutamine metabolism. Meanwhile, we discovered that concentration of glutamine in tumor necrotic zone of treatment group was lower than that in control group, which shows that the bacteria affected the glutamine metabolism(Research basis). What is the theory of bacteria affect the glutamine metabolism(Scientific issues)? One of the scientific hypothesis is the bacteria absorbs glutamine in the tumor as competition for nutrients. The other scientific hypothesis is that glutamine bacteria change the environment of tumor and then affects the glutamine metabolism. In this project, we will detect the environmental change in the tumor in the process of bacterial tumor therapy, which provides the evidences to establish a microfluidic system for mimic the tumor with the advantages of environment stability and quantitatively describe. A new bacterial strain with no metabolic function of glutamine will be constructed and test in the new microfluidic system to test the hypothesis, and then solving scientific problem. This project will present a new method for optimize bacterial tumor therapy.

细菌疗法是通过直接杀伤、激活免疫等机制成为肿瘤治疗的新型热门疗法。预实验研究证实了沙门氏菌可以靶向肿瘤区域并抑制肿瘤生长；低浓度谷氨酰胺对膀胱癌细胞(MB49)生长有抑制作用，所以有望通过影响实体瘤内谷氨酰胺代谢抑制肿瘤生长。同时我们发现：细菌治疗组肿瘤坏死区内的谷氨酰胺含量明显少于对照组，即瘤内谷氨酰胺代谢受到了细菌影响(研究基础)。那么，细菌影响肿瘤微环境内谷氨酰胺代谢的机制是什么(科学问题)？结合文献与预实验我们提出两种科学假说：1)细菌是通过营养竞争摄取瘤内谷氨酰胺；2)细菌改变瘤内环境影响谷氨酰胺代谢。本项目拟探索细菌肿瘤治疗过程中肿瘤内环境各成分变化，指导搭建环境稳定可定量的模拟肿瘤环境的微流控芯片，构建不代谢谷氨酰胺的缺陷型菌株，在体外定量平台中验证科学假说，从而揭示细菌影响肿瘤内谷氨酰胺代谢的机制。本项目的完成将为优化细菌治疗肿瘤的方法提供新的思路。

细菌肿瘤治疗过程中，肿瘤内谷氨酰胺代谢受到明显影响。基于以上观察，本项目首先明确了细菌肿瘤治疗过程中肿瘤内环境各成分变化、成功建立模拟肿瘤内治疗环境的单一变量平台，定量分析了小鼠肿瘤内游离氨基酸、pH值、氧气水平的时空分布变化，完成细菌治疗肿瘤微环境评测。利用仿真软件重现肿瘤内营养环境，仿真软件对初步设计的微流控芯片进行溶质交换计算，计算芯片内的各项条件参数。按仿真指导参数对芯片进行多次设计、加工及评测，最终建立微流控实验平台模拟细菌肿瘤治疗的体外环境。并基于以上信息建立体外实体瘤环境仿真模型、搭建环境稳定可定量的重现实体瘤内环境微流控芯片，构建不代谢谷氨酰胺缺陷型菌株与动物模型。进一步揭示细菌影响肿瘤微环境内谷氨酰胺代谢的机制，成功回答了细菌影响肿瘤微环境内谷氨酰胺代谢的机制这一科学问题。项目涉及微流控器件的工程学、细胞体外建模的生物学、肿瘤治疗的医学及构建菌株的合成生物学等多个学科领域的基本理论与分析方法，具有多学科交叉与融合特性。具有重要的意义。