Engineered Salmonella-based therapeutic delivery system for localized TRAIL and IL-2 expression in colorectal cancer

Targeted bacterial gene delivery systems have emerged as promising strategies for localized cancer therapy by enabling selective intratumoral expression of therapeutic molecules while reducing systemic toxicity. In this study, attenuated Salmonella typhimurium SL3261 strains were engineered to express tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and interleukin-2 (IL-2) under control of the hypoxia-responsive nirB promoter, and their antitumor effects were evaluated in colorectal cancer models. Recombinant protein expression was confirmed by fluorescence analysis and ELISA under oxygen-restricted conditions. Antitumor activity was assessed in HCT-8 colorectal cancer cells through viability assays, nitric oxide quantification, and apoptosis analysis. In vivo therapeutic efficacy was evaluated in BALB/c nude mice bearing HCT-8 xenografts following intratumoral administration of recombinant strains. Recombinant protein-containing supernatants significantly reduced tumor cell viability and increased apoptotic and necrotic populations. IL-2-containing treatments were associated with increased nitric oxide production. In vivo, recombinant Salmonella strains significantly inhibited tumor progression and reduced tumor weight, with combined TRAIL and IL-2 therapy demonstrating enhanced antitumor efficacy. Histological analyses revealed extensive tumor necrosis, while biodistribution assays demonstrated preferential intratumoral bacterial accumulation. These findings support engineered Salmonella -based systems as promising localized platforms for combinatorial cancer immunotherapy.