利用基因工程益生菌早期防治结直肠癌的研究

Preventive treatment of colorectal cancer can greatly improve the health and prognosis of patients with high-risk colon cancer. Increasing the level of butyrate in the colon is a potential strategy for preventive treatment of colorectal cancer, since butyrate can inhibit the growth of colorectal tumors, repair intestinal barrier and promote the intestinal microecology. There are currently three common means of increasing the concentration of butyric acid in the colon, e.g., oral intake of butyrate, enema butyrate or oral intake of butyrate producing bacteria. However, none of them are able to release butyrate in the colon in a highly specific, safe and stable way. To address these challenge, the applicant proposes to use genetically engineered probiotics to treat colorectal cancer early. The probiotic bacteria with strong colonization ability and high biosafety are used as drug carriers, and the exogenous butyrate synthesis module is introduced into the probiotics. The recombinant probiotics are orally administered to modulate the colorectal microenvironment in a safe, effective and durable way. Abundant butyrate secreted by the synthetic probiotics could permanently inhibits the development of colorectal tumor, and would effectively prevent colorectal cancer early. This project will promote the development of standardized artificial probiotics to regulate the intestinal microenvironment, reveal the mechanism of butyrate in inhibiting the growth of colorectal tumors, and facilitate the development of precise medical technology to treat diseases related to intestinal microbiota disorders.

早期防治结直肠癌，可以极大地提高结直肠癌高危人群的健康水平和预后生存率。增加结直肠内的丁酸水平，是早期防治结直肠癌的潜在手段，可以抑制结直肠肿瘤生长、修复肠道屏障功能、改善肠道微生态等。目前有三种常见的增加结直肠内丁酸浓度的手段，口服丁酸、灌肠丁酸或口服丁酸生产菌，均难以实现靶向结直肠道、安全、稳定地释放丁酸。针对这些问题，申请人研究在生物安全性高、结直肠道定殖能力强的益生菌内，集成外源的丁酸合成功能模块，发展基于人工益生菌在结直肠内给药丁酸的新方法。经口服后，所构建的益生菌可以安全、稳定地释放丁酸，持久地抑制促进结直肠肿瘤生长的微环境，从而有效地预防结直肠癌。本项目提供了一种基于人工益生菌早期防治结直肠癌的新思路，模块加载式的人工益生菌设计，有助于揭示结直肠道丁酸水平抑制结直肠肿瘤生长的机理，促进发展肠道微生态失调相关疾病的个性化、模块化的人工益生菌治疗技术。

本项目开展了高产丁酸的基因工程益生菌理性构建与丁酸影响结直肠癌和结直肠炎发展的分子机制研究。其主要成果包括：通过构建外源丁酸合成途径、敲除竞争途径、整合基因组以及优化限速步骤等，成功构建了一株高产丁酸的基因工程益生菌，产量为相同底盘菌目前报道最高值；研究了丁酸盐抑制结肠癌细胞生长的分子机制，揭示了丁酸盐通过抑制AKT信号通路抑制结直肠癌葡萄细胞葡萄糖摄取，并发展了一种丁酸联用5-FU增强结直肠癌化疗敏感性的联合用药策略；揭示肠道丁酸抑制结直肠炎发展的与宿主上皮互作的分子机制，丁酸通过抑制关键靶基因Gsdmd来缓解肠炎发展。综合上述结果，本研究构建了一株具有抑制结直肠炎和结直肠癌潜力的基因工程益生菌，研究结果促进理解丁酸在结直肠炎、结直肠癌发展中与宿主互作的分子机理。项目资助已正式发表SCI论文2篇，待投稿高水平论文1篇，已申请国家发明专利1项，正在申请PCT。培养博士研究生2名，硕士研究生3名。项目投入经费25万元，支出16.86万元，各项支出基本与预算相符。剩余经费8.14万元，剩余经费计划用于本项目研究后续支出。