Chemokine CCL5 overexpression combined with radiotherapy modulates Th1-mediated immune response and leads to significant tumor growth delay in mouse tumor models

This study investigated the antitumor efficacy of chemokine CCL5 gene therapy using gene electrotransfer (GET) in combination with radiotherapy (RT) in solid murine tumors CT26 and 4T1. In vitro, CT26 and 4T1 tumor cells transfected with plasmid DNA (pDNA) encoding CCL5 induced migration of RAW264.7 macrophages. In vivo, CCL5 overexpression achieved via GET of pDNA encoding CCL5 led to increased splenocyte infiltration in dorsal window chamber models. When combined with RT, GET of pDNA encoding CCL5 shifted the tumor cytokine profile toward a proinflammatory state, with elevated Ifn-γ, Cxcl9, Cxcl10, and Il-12α. Although CD8 + and CD4 + T cells were reduced post-treatment, due to radiation-induced cell death, the combination of GET of pDNA encoding CCL5 and RT significantly delayed tumor growth in both models. In 4T1 tumors, this delay was also significant compared to the equivalent treatment with GET of control pDNA. These findings support GET of pDNA encoding CCL5 combined with RT as a strategy to enhance immune-mediated tumor control.