Gene therapy increases MHC class-I and T cell Infiltration to promote anti-tumor immune response in 4T1 breast cancer model

Abstract

Abstract Background Immune checkpoint inhibition (ICI) has led to impressive gains in survival for many patients. However, many cancer patients treated with ICI experience intrinsic or acquired resistance which directly affects efficacy. Decreased levels of MHC class-I molecules on cancer cells and tumor infiltrating lymphocytes (TILs) have been associated with poor clinical outcomes. Methods Treatment of breast cancer cell lines with a plasmid encoding IL-12 (pIL-12) and vector pUMVC3 were analyzed using flow cytometry, western blotting and then validated functionally. The 4T1 breast cancer animal model was used to study T cell infiltration into the tumor as well as response following local delivery of pIL-12 with electrotransfer. Results Enhanced MHC class-I expression in 4T1 tumor cells, and elevated CD8+ T-cell infiltration into 4T1 tumor tissue were observed after pIL-12 gene electrotransfer. Furthermore, increased capacity to lyse 4T1 cells was observed with cultured cytotoxic T lymphocytes (CTLs) from long-term surviving mice compared to control group. A direct translation was observed in tumor-bearing mice, including attenuating tumor growth and improved tumor-free survival in mice. An immune memory response which protected against rechallenge was induced also. Conclusion Our findings suggest that the capacity of an induced endogenous immune response with pIL12 via the recruitment of CD8+ T cells and increased MHC class-I expression in tumor cells results in attenuating the resistance of anti-PD1 and leads to eradication of established, aggressive tumors and generates systemic tumor-specific protective immunity. Combinations of anti-PD-1 with pIL-12 gene therapy may be an effective future therapeutic strategy. Supported by NCI R01 CA186730