传统癌症治疗的局限性要求我们使用以靶向为导向、高度侵袭和安全的治疗方法。因此，沙门氏菌天然的抗肿瘤活性可以提供更好的选择来对抗癌症。本研究旨在利用弱毒化的沙门氏菌，并利用定量感应（QS）信号传递系统将细胞溶解蛋白细胞溶解素A（ClyA）定位在肿瘤中的精确局部表达，而不是在健康的器官中表达。治疗传递菌株通过trpA和trpE基因的缺失，通过pagL和rfaL基因的缺失，改变了脂质A和O-抗原，利用λ红重组方法进行选择性肿瘤定植。该菌株转化为设计的QS受控ClyA表达载体，并通过Western blot进行验证。经过体内传代的治疗菌株用于每周一次的四次癌症治疗，剂量为5×106 CFU/只小鼠。弱毒化菌株在小鼠中早期暴露后，诱导的内毒素相关细胞因子TNF-α、IL-1β和IFN-γ最小化，尽管如此，在小鼠体内仍显示了充足的定植能力。通过Western blot从不同细菌密度培养的细菌培养物中进一步确认了QS受控的ClyA表达。结果表明，在脾脏、肝脏和肺脏被排空后，体内传代菌株更倾向于定植在肿瘤上，没有留下外观上的组织瘢痕。设计的构建体在小鼠CT26结肠癌模型中的抗癌效果得到了评估。与空载体对照相比，ClyA的表达使肿瘤杀伤活性提高了67%。因此，通过在达到阈值细菌细胞密度后激活QS，ClyA的表达改善了工程沙门氏菌株的抗肿瘤效果。进一步，对肿瘤和其他器官的免疫组化染色证实了QS控制的肿瘤特异性ClyA表达。总体而言，结果表明，开发出的抗癌沙门氏菌具有低内毒素性和QS受控的ClyA表达，这些都是有益的安全元素，并支持通过O-抗原缺乏来进行沙门氏菌接种的复发。版权所有 © 2023. Elsevier B.V. 生产和托管。

The limitations of conventional cancer therapies necessitate target-oriented, highly invasive, and safe treatment approaches. Hence, the intrinsic anti-tumor activity of Salmonella can offer better options to combat cancers.This study aims to utilize attenuated Salmonella and deliver cytolytic protein cytolysin A (ClyA) under quorum sensing (QS) signaling for precise localized expression in tumors but not in healthy organs.The therapeutic delivery strain was imposed with tryptophan auxotroph for selective colonization in tumors by trpA and trpE deletion, and lipid-A and O-antigen were altered by pagL and rfaL deletions using lambda red recombination method. The strain was transformed with the designed QS-controlled ClyA expression vector which was validated by western blot. The in vivo passaged therapeutic strain was used for treatment four times at a weekly interval, with a dose of 5×106 CFU/mouse for cancer therapy.The attenuated strain induced minimal endotoxicity-related cytokines TNF-α, IL-1β, and IFN-γ and exhibited adequate colonization despite earlier exposure in mice. The QS-controlled ClyA expression was confirmed by western blot from bacterial cultures grown at different cell densities. The results demonstrated that the in vivo passaged strain preferentially colonized the tumor after vacating the spleen, liver, and lung, leaving no outward histological scars. The anti-cancer effect of the designed construct was evaluated in the murine CT26 colon cancer model. The expression of ClyA increased tumoricidal activity by 67% compared to vector control.Hence, the anti-tumor effect of the engineered Salmonella strain was improved by ClyA expression via QS activation after achieving the threshold bacterial cell density. Further, immunohistochemical staining of the tumor and other organs corroborated the QS-controlled tumor-specific expression of ClyA. Overall, the results imply that the developed anti-cancer Salmonella has low endotoxicity and QS-controlled expression of ClyA as beneficial safety elements and supports recurrent Salmonella inoculation by O-antigen deficiency.Copyright © 2023. Production and hosting by Elsevier B.V.