The Antitumor Efficacy And Mechanism Of Chimeric Antigen Receptor Engineered T Cells Targeting Tumor-specific Epitope Of EGFR

Chimeric antigen receptor engineered T（CAR-T）cells have gained great successes in hematological malignancies,whereas still remain plenties of challenges in soild tumors.Tumor-specific epitope of EGFR^287-302 is only fully exposed on the unnormally activated EGFR or variants of EGFR such as EGFRv III on the surface of some tumor cells,but not in normal tissues,which makes it a perfect target for CAR-T therapy.It is reported that 31～64%of glioblastoma（GBM）patients are EGFRv III positive,approximately 60%of triple negative breast cancer（TNBC）patients are EGFR positive.In this syudy,we construct 806-m28Z-CAR T cells targeting EGFR^287-302 tumor specific antigen epitope successfully.Notably,806-m28Z-CAR T cells significantly lyse GL261/EGFRv III GBM cells in vitro and in vivo in a dose-dependent manner.Low dose 806-28Z-CAR T cells could suppress the growth of GL261/EGFRv III xenografts,whereas high dose 806-28Z-CAR T cells could completely eradicate xenograft tumors.Moreover,additional rechallenge experiments indicate that GL261/EGFRv III cells or parental GL261 cells could not grow in the cured mice.Concentrations of granzyme B in mice plasma are correlated positively with CAR-T cells infusion quantity.These results suggest that the effector to target ratio is a crucial determinant for CAR-T efficacy against EGFRv III-expressing GBM and granzyme B release may be a predictive marker for the antitumor efficacy of CAR-T cells.In orthotopic breast cancers models,the efficacy of CAR-T cells therapy is limited.A combined treatment with CAR-T therapy and radiotherapy（RT）was performed to improve the antitumor effect in C57BL/6 and Balb/c orthotopic triple negative breast cancer（TNBC）xenografts models.In comparison with single treatment of CAR-T cells or radiation,the combination therapy has shown significant improvement of tumor growth inhibition and prolongs survival of mice.Infusion of CAR-T cells on the same day after single high dose radiotherapy is the best combination method that we have explored.Mechanistically,CAR-T therapy combined with radiotherapy could increase infiltration of CAR-T cells and NK cells into tumor tissues in comparison with either single treatment.These data indicate that CAR-T therapy combined with radiotherapy could enhance antitumor efficacy and may be used as a new therapeutic strategy for clinical cancer treatment.