Reprogramming CD19-Specific T Cells with IL-21 Signaling Can Improve Adoptive Immunotherapy of B-Lineage Malignancies

Abstract

Improving the therapeutic efficacy of T cells expressing a chimeric antigen receptor (CAR) represents an important goal in efforts to control B-cell malignancies. Recently an intrinsic strategy has been developed to modify the CAR itself to improve T-cell signaling. Here we report a second extrinsic approach based on altering the culture milieu to numerically expand CAR⁺ T cells with a desired phenotype, for the addition of interleukin (IL)-21 to tissue culture improves CAR-dependent T-cell effector functions. We used electrotransfer of Sleeping Beauty system to introduce a CAR transposon and selectively propagate CAR⁺ T cells on CD19⁺ artificial antigen-presenting cells (aAPC). When IL-21 was present, there was preferential numeric expansion of CD19-specific T cells which lysed and produced IFN-γ in response to CD19. Populations of these numerically expanded CAR⁺ T cells displayed an early memory surface phenotype characterized as CD62L⁺CD28⁺ and a transcriptional profile of naïve T cells. In contrast, T cells propagated with only exogenous IL-2 tended to result in an overgrowth of CD19-specific CD4⁺ T cells. Furthermore, adoptive transfer of CAR⁺ T cells cultured with IL-21 exhibited improved control of CD19⁺ B-cell malignancy in mice. To provide coordinated signaling to propagate CAR⁺ T cells, we developed a novel mutein of IL-21 bound to the cell surface of aAPC that replaced the need for soluble IL-21. Our findings show that IL-21 can provide an extrinsic reprogramming signal to generate desired CAR⁺ T cells for effective immunotherapy. Cancer Res; 71(10); 3516–27. ©2011 AACR.