Injectable microgels containing genetically engineered bacteria for colon cancer therapy through programmed Chemokine expression

Chemokines are emerging as important targets for cancer immunotherapy due to their role in regulating immune cell migration and activation within the tumor microenvironment. Effective delivery and sustained presence of chemokines at the tumor site is essential for recruiting and activating immune cells to exert anti-tumor effects. In this study, we report a genetically engineered bacterial cell factory designed for the continuous production of chemokine CCL21 in a controlled manner. To decrease the formation of infusion bodies (IBs) in bacteria, we used thioredoxin (Trx) as the fusion partner and cloned at N-terminal of the target protein. The commonly used promoters, pT7-LacO, pBV220, and pDawn, were employed to explore the influence of various inducers on the expression of CCL21 in bacteria. The engineered bacteria were finally encapsulated within spherical gelatin methacryloyl (GelMA) microgels, which not only maintained bacterial viability but also prolonged their retention in the intestines of mice. As a result, the sustained presence and localized production of CCL21 led to effective suppression of tumor growth.