Abstract 937: Nr4a transcription factors limit CAR T-cell function in solid tumors

In cancer immunotherapy, CD19-targeted CAR T cells have exhibited impressive clinical efficacy against B cell leukemias and lymphomas; however, they have been less effective against solid tumors. This is in part because CAR T cells enter a hyporesponsive (“exhausted” or “dysfunctional”) state that is triggered by chronic antigen stimulation and characterized by upregulation of several inhibitory surface receptors and loss of effector function. To identify transcriptional regulators and other candidates contributing to the diminished CAR T cell function in solid tumors, we developed a CAR T cell model in which recipient mice bearing murine melanoma tumors expressing human CD19 were adoptively transferred with CD19-targeted CAR T cells. We demonstrate that in both CD8+ CAR T tumor-infiltrating lymphocytes (TILs) and endogenous CD8+ TILs expressing high levels of PD-1 and TIM3, the Nr4a proteins Nr4a1 (Nur77), Nr4a2 (Nurr1), and Nr4a3 (Nor1) are prominent effectors of the transcriptional program downstream of NFAT: they promote the expression of inhibitory receptors and genes associated with early hyporesponsive state, and limit effector function. Most importantly, treatment of tumor-bearing mice with CD8+ CAR T cells lacking all three Nr4a factors (Nr4aTKO) resulted in tumor regression and prolonged survival. Nr4aTKO CD8+ CAR T TILs displayed a transcriptomic profile characteristic of effector function, including upregulation of granzymes and cytokines, and many of these gene expression changes were associated with altered regulatory element accessibility near effector genes. Our data identify Nr4a transcription factors as major players in the cell-intrinsic program of T cell hyporesponsiveness and point to Nr4a inhibition as a promising strategy for cancer immunotherapy. Citation Format: Joyce Chen, Isaac F. Lopez-Moyado, Hyungseok Seo, Chan-Wang J. Lio, Laura J. Hempleman, Takashi Sekiya, Akihiko Yoshimura, James P. Scott-Browne, Anjana Rao. Nr4a transcription factors limit CAR T-cell function in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 937.