Differential Susceptibility and Role for Senescence in Cart Cells Based on Costimulatory Domains

Abstract

Despite the success of chimeric antigen receptor T (CART) cell therapy in hematological malignancies, durable remissions remain low. Here, we report CART senescence as a potential resistance mechanism in 41BB-costimulated CART cell therapy. To mimic cancer relapse, we utilized an in vitro model with repeated CART cell activation cycles followed by rest periods. Using CD19-targeted CART cells with costimulation via 4-1BB-CD3 zeta (BB zeta) or CD28-CD3 zeta (28 zeta), we showed that CART cells undergo functional, phenotypical, and transcriptomic changes of senescence, which is more prominent in BB zeta. We then utilized two additional independent strategies to induce senescence through MYC activation and irradiation. Induction of senescence impaired BB zeta activity but improved 28 zeta activity in preclinical studies. These findings were supported by analyses of independent patient data sets; senescence signatures in CART cell products were associated with non-response to BB zeta but with improved clinical outcomes in 28 zeta treatment. In summary, our study identifies senescence as a potential mechanism of failure predominantly in 41BB-costimulated CART cells.