C3aR costimulation enhances antitumor efficacy of CAR-T through promoting Th17 expansion and memory T phenotype

Chimeric antigen receptor (CAR)-modified adoptive T-cell therapy is a promising immunotherapy for hematologic malignancies. However, the efficacy in extramedullary leukemia is still limited and new strategies with improved anti-tumor activity are highly needed. Since C3aR activation builds a bridge between innate immune and adaptive immune and it could trigger Th17 response, we hypothesized that C3aR incorporation as costimulatory domain would augment anti-tumor activity of CAR-T. To address this possibility, we introduced a genetically engineered construct, comprising the domain of C3aR into CAR-T cells. The generated BB-ζ-C3aR CAR-T exhibited potent cytolytic ability to eradicate various tumor cells expressing CD19 or BCMA in vitro . When administrated intravenously into the xenografts leukemia NCG mice who received CD19 + or BCMA + expressing tumor cells, BB-ζ-C3aR CAR-T cells reduced the tumor burden and improved the survival of mice. Of note, these BB-ζ-C3aR CAR-T cells could effectively eradicate subcutaneous CD19 + tumor cells, highlighting the potential therapy for extramedullary leukemia. Mechanistically, the BB-ζ-C3aR CAR-T cells preferred to exhibit tumor-killing Th17 phenotype and suppressed the tumor-tolerated Treg function. In addition, the induction of memory T cells phenotype in BB-ζ-C3aR CAR-T group indicated their long duration effects. Taken together, our findings suggest that the application of C3aR costimulation to boost CAR-T-cell activity is efficacious against aggressive tumor cells via Th17 expansion and memory T cell induction.