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 receptors and loss of effector function. To identify transcriptional regulators and other candidates contributing to the diminished function of CAR T-cells in solid tumors, we developed a CAR T-cell model in which recipient mice bearing murine melanoma tumors expressing the human CD19 antigen were adoptively transferred with CD19-targeted CAR T-cells. Genome-wide analyses of these mouse tumor-infiltrating lymphocytes (TILs) showed that endogenous CD8+ TILs and CAR T TILs selected for expression of high levels of PD-1 and TIM3 exhibited similar profiles of gene expression and chromatin accessibility, associated with secondary activation of the Nr4a nuclear receptor family of transcription factors by the transcription factor NFAT. We demonstrate that in both CAR T TILs and endogenous CD8+ TILs, 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 stages of the exhausted/ dysfunctional state, and limit effector function. Most importantly, treatment of tumor-bearing mice with CAR T-cells lacking all three Nr4a transcription factors (Nr4aTKO) resulted in tumor regression and prolonged survival. Nr4aTKO tumor-infiltrating CAR T-cells displayed a gene expression profile characteristic of effector function, including increased expression of granzymes, cytokines and the transcription factor T-bet. 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, James P. Scott-Browne, Isaac F. Lopez-Moyado, Laura J. Hempleman, Hyungseok Seo, Takashi Sekiya, Akihiko Yoshimura, Anjana Rao. Nr4a transcription factors limit CAR T-cell function in solid tumors [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A178.