A novel recombinant attenuated Salmonella carrying RGD and melittin genes induces apoptosis of B16 cells and inhibits melanoma growth.

The tumor provides a favorable microenvironment for the growth of anaerobes and facultative anaerobes, such as Salmonella. Melittin (MEL) is a major component of bee venom that has a distinct inhibitory effect on tumor cell metastasis and invasion, but its clinical application is limited owing to non-specific cytotoxicity. Arg-Gly-Asp (RGD) is a potent competitive antagonist of extracellular matrix binding to αvβ3, and is often used as a tumor-targeting marker. Here, we engineered Salmonella typhimurium to selectively express and release RGD-MEL. The engineered bacteria were intratumourally injected into mice bearing B16 melanoma xenografts. We observed that RGD-mediated expression and release of MEL by S. Typhimurium promoted apoptosis while inhibiting B16 cell proliferation, migration, chemotaxis, and invasion. LH430/pRGD-MEL also had a prominent inhibitory effect on solid tumors. By leveraging the combined mechanisms of RGD and S. Typhimurium, LH430/pRGD-MEL demonstrates enhanced accumulation and expression within tumor tissues. Furthermore, no signs of tumor cell metastasis or noticeable lesions were observed in the liver and lungs. Notably, the mice treated with LH430/pRGD-MEL exhibited significantly prolonged survival. RNA sequencing analysis revealed that engineered S. Typhimurium primarily disrupted the immune barrier within tumor tissue and inhibited tumor growth by upregulating apoptosis and phagocytosis-related pathways. These results indicate that LH430/pRGD-MEL demonstrates strong tumor-targeting capacity, minimizes host toxicity, and exhibits significant tumor-suppressive effects by promoting tumor cell apoptosis, highlighting the translational potential of microbial-mediated precision oncology strategies.