Expression analysis of chimeric antigen receptor-transduced T cells following antigenic stimulation

Adoptive transfer of anti-CD19 chimeric antigen receptor (CAR)-engineered T cells has shown impressive clinical responses in patients with refractory B-cell malignancies. However, therapeutic effects of CAR-T cells targeting other hematologic malignancies and solid tumors are not yet satisfactory. Although inefficient tumor trafficking and multiple immunosuppressive molecules impede CAR-T cell effector responses, signals delivered by the current CAR constructs may still be insufficient to fully activate antitumor T cell functions. Optimal T cell activation and proliferation requires multiple signals including T cell receptor (TCR) engagement (signal 1), costimulation (signal 2), and cytokine engagement (signal 3). CAR genes developed to date contain a CD3z domain and costimulatory domain(s), but not a domain to transmit signal 3. In this study, we have developed a novel CAR construct capable of inducing cytokine signaling in an antigen-dependent manner. The new generation CD19 CAR encodes a cytoplasmic domain of IL-2RB and STAT3-binding YXXQ motif together with CD3z and CD28 domains (28-IL2RB-z (YXXQ)). The 28-IL2RB-z (YXXQ) CAR-T cells showed antigen-dependent JAK-STAT, especially the STAT3-mediated pathway activation, which promoted their proliferation and prevented terminal differentiation. The 28-IL2RB-z (YXXQ) CAR-T cells demonstrated superior in vivo persistence and antileukemia effects compared with the currently used CARs in multiple tumor models. Human CD8+ T cells derived from three different healthy donors were retrovirally transduced with individual anti-CD19 CAR genes (28-z, 28-BB-z and 28-IL2RB-z (YXXQ)) and were stimulated with K562 cells expressing CD19. RNA was collected 4 days after stimulation and gene expression profiles were analyzed by Affymetrix Human Gene 2.0 ST Array (gene-level analysis).