阿霉素负载的杂化生物体级联提升瘤内活性氧并激活机体的抗肿瘤免疫应答

微生物具有自驱动富集在肿瘤处的特性，可以作为抗肿瘤药物靶向递送的天然载体。目前大多数基于微生物的制剂，单一利用化学方法在菌表面修饰化疗药物或应用基因工程手段使细菌表达具有肿瘤杀伤性的相关蛋白。然而单一疗法并不能取得理想的临床疗效，因此，本课题基于“杂化生物体”概念，将阿霉素负载在具有生物催化功能的工程菌表面形成杂化生物体，级联催化提升肿瘤处活性氧水平，同时激活机体的肿瘤免疫，增强由阿霉素介导的抗肿瘤效果。首先通过基因工程的方法在工程菌内表达葡萄糖脱氢酶（GDH），然后负载阿霉素。该杂化生物体可自发地驱动到肿瘤处，细菌高表达GDH在肿瘤组织中催化产生还原型烟酰胺腺嘌呤二核苷酸磷酸（NADPH），而阿霉素激活胞内NADPH氧化酶，大量NADPH在其氧化酶的作用下产生高浓度活性氧。在杀伤性高浓度活性氧和化疗药阿霉素的协同作用下，实现最佳的抗肿瘤治疗效果，同时很大程度上增强机体的抗肿瘤免疫应答。

Microorganism preferentially self-accumulating in tumor can be utilized as natural vehicles for tumor targeting. At present, neither current chemical nor genetic approaches alone can clinically satisfy the requirements on high clinical efficiency. Here, this project proposes a concept of hybrid bacteria where doxorubicin (DOX) is conjugated into the surface of engineered Escherchia coli (E. coli) with bio-catalytic function to increase the in vivo reactive oxygen species (ROS) level in tandem for effective cancer immunotherapy and tumor-growth inhibition. Following the injection, the nicotinamide adenine dinucleotide phosphate (NADPH) is produced by GDH from E. coli and promotes the generation of intratumoral toxic reactive oxygen species (ROS), which is catalyzed by the DOX-activated NADPH oxidases. In the tumor models, the hybrid bacteria effectively inhibit tumor growth, and endow stimulated systemic antitumor immune responses, leading to the eradication of the tumor.