Neoantigen-Augmented iPSC-based Cancer Vaccine Combined with Local Radiotherapy Promotes Systemic Antitumor Immunity in Poorly Immunogenic Cancers

Although irradiated induced-pluripotent stem cells (iPSCs) as a prophylactic cancer vaccine elicit an antitumor immune response, the therapeutic efficacy of iPSC-based cancer vaccines is not promising due to their insufficient antigenicity and the immunosuppressive tumor microenvironment. Here, we found that neoantigen-engineered iPSC cancer vaccines can trigger neoantigen-specific T cell responses to eradicate cancer cells and increase the therapeutic efficacy of RT in poorly immunogenic colorectal cancer (CRC) and triple-negative breast cancer (TNBC). We generated neoantigen-augmented iPSCs (NA-iPSCs) by engineering AAV2 vector carrying murine neoantigens and evaluated their therapeutic efficacy in combination with radiotherapy. After administration of NA-iPSC cancer vaccine and radiotherapy, we found that ~60% of tumor-bearing mice achieved a complete response in microsatellite-stable CRC model. Furthermore, splenocytes from mice treated with NA-iPSC plus RT produced high levels of IFN secretion in response to neoantigens and had a greater cytotoxicity to cancer cells, suggesting that the NA-iPSC vaccine combined with radiotherapy elicited a superior neoantigen-specific T-cell response to eradicate cancer cells. The superior therapeutic efficacy of NA-iPSCs engineered by mouse TNBC neoantigens was also observed in the syngeneic immunocompetent TNBC mouse model. We found that the risk of spontaneous lung and liver metastasis was dramatically decreased by NA-iPSCs plus RT in the TNBC animal model. Altogether, these results indicated that autologous iPSC cancer vaccines engineered by neoantigens can elicit a high neoantigen-specific T-cell response, promote tumor regression and reduce the risk of distant metastasis in combination with local radiotherapy. Examination of expression and mutation-associated antigens (neoantigens) profile of murine (CT26) colorectal cancer cells treated with iPSC cancer vaccine (iPSC-Vac). In the experiment, the impact of mouse irradiated iPSC cancer vaccine on neoantigen-bearing gene profiles was monitored. The experiment had 2 samples (CT26, CT26-iPSC-Vac). CT26 samples were used as the reference sample to compare. An analysis was also performed on RNA extracted from tumor samples (CT26 cells grown in the back of Balb/c mice, subcatenous injected with mouse irradiated iPSC cancer vaccine).