Engineered exosome-like nanovesicles suppress tumor growth by reprogramming tumor microenvironment and promoting tumor ferroptosis

Tumor vaccines that induce effective and sustained antitumor immunity are highly promising for cancer therapy. However, the antitumor potential of these vaccines is weakened due to the immunosuppressive characteristics of the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) are the most abundant stromal cells within the TME; they play an important role in tumor growth, metastasis, immunosuppression, and drug resistance. Fibroblast activation protein-α (FAP) is overexpressed in CAFs in more than 90% of human tumor tissues. Further, FAP+CAFs are an ideal interstitial target for the immunotherapy of solid tumors. Exosomes derived from tumor cells contain many tumor antigens, which can be used as the basis of tumor vaccines that elicit strong antitumor immunity. Almost all exosome-based cancer vaccines have been designed and developed for tumor parenchymal cells. Moreover, the exosome production is very low and the purification is very difficult, limiting their clinical application as tumor vaccines. In this study, we developed FAP gene–engineered tumor cell–derived exosome-like nanovesicles (eNVs-FAP) as a tumor vaccine that can be prepared easily and in large quantities. The eNVs-FAP vaccine inhibited tumor growth by inducing strong and specific cytotoxic T lymphocyte (CTL) immune responses against tumor cells and FAP+CAFs and reprogramming the immunosuppressive TME in the colon, melanoma, lung, and breast cancer models. Moreover, eNVs-FAP vaccine–activated cellular immune responses could promote tumor ferroptosis by releasing interferon-gamma (IFN-γ) from CTLs and depleting FAP+CAFs. Thus, eNVs-FAP is a candidate tumor vaccine targeting both the tumor parenchyma and the stroma.