Researchers from Shandong University in China have engineered the probiotic bacterium Escherichia coli Nissle 1917 (EcN) to function as a targeted drug delivery system for cancer treatment. By genetically modifying EcN, the team enabled it to biosynthesize romidepsin (also known as FK228), an FDA-approved histone deacetylase inhibitor with potent anticancer properties. In experiments, these modified bacteria accumulated preferentially inside solid tumors in mice, particularly in a breast cancer xenograft model using 4T1 cells, where they produced and released the drug directly at the tumor site. This approach leverages the natural tumor-colonizing ability of EcN, combined with localized drug production, to create a dual-action therapy: the bacteria induce an inflammatory response that supports anticancer activity, while romidepsin exerts its therapeutic effects with reduced systemic exposure. Results showed improved treatment efficacy compared to wild-type EcN, along with lower cardiotoxicity and mortality associated with romidepsin when delivered systemically. The strategy highlights the potential of synthetic biology in bacteria-mediated cancer therapy, offering more precise drug delivery that could minimize side effects common in traditional chemotherapy. However, the study emphasizes that this remains preclinical work in mice, with significant further research required to assess safety, bacterial clearance after treatment, potential immune responses, and translation to human trials. The findings establish a foundation for developing engineered bacteria as living factories for small-molecule anticancer agents in targeted therapies.