Anti-tumor effects of DNA vaccine targeting human fibroblast activation protein α by producing specific immune responses and altering tumor microenvironment in the 4T1 murine breast cancer model.

Fibroblast activation protein α (FAPα) is a tumor stromal antigen overexpressed by cancer-associated fibroblasts (CAFs). CAFs are genetically more stable compared with the tumor cells and immunosuppressive components of the tumor microenvironment, rendering them excellent targets for cancer immunotherapy. DNA vaccines are widely applied due to their safety. To specifically destroy CAFs, we constructed and examined the immunogenicity and anti-tumor immune mechanism of a DNA vaccine expressing human FAPα. This vaccine successfully reduced 4T1 tumor growth through producing FAPα-specific cytotoxic T lymphocyte responses which could kill CAFs, and the decrease in FAPα-expressing CAFs resulted in markedly attenuated expression of collagen I and other stromal factors that benefit the tumor progression. Based on these results, a DNA vaccine targeting human FAPα may be an attractive and effective cancer immunotherapy strategy.