NOTCH1 signaling during CD4+ T-cell activation alters transcription factor networks and enhances antigen responsiveness

•NOTCH1 signaling restricts naïve CD4+ T-cell differentiation and enhances CD4+ CAR-T proliferation and helper function.•NOTCH1 signaling programs distinct cytokine profiles in naïve CD4+ T cells by inducing AhR and c-MAF. [Display omitted] Adoptive transfer of T cells expressing chimeric antigen receptors (CAR-T) effectively treats refractory hematologic malignancies in a subset of patients but can be limited by poor T-cell expansion and persistence in vivo. Less differentiated T-cell states correlate with the capacity of CAR-T to proliferate and mediate antitumor responses, and interventions that limit tumor-specific T-cell differentiation during ex vivo manufacturing enhance efficacy. NOTCH signaling is involved in fate decisions across diverse cell lineages and in memory CD8+ T cells was reported to upregulate the transcription factor FOXM1, attenuate differentiation, and enhance proliferation and antitumor efficacy in vivo. Here, we used a cell-free culture system to provide an agonistic NOTCH1 signal during naïve CD4+ T-cell activation and CAR-T production and studied the effects on differentiation, transcription factor expression, cytokine production, and responses to tumor. NOTCH1 agonism efficiently induced a stem cell memory phenotype in CAR-T derived from naïve but not memory CD4+ T cells and upregulated expression of AhR and c-MAF, driving heightened production of interleukin-22, interleukin-10, and granzyme B. NOTCH1-agonized CD4+ CAR-T demonstrated enhanced antigen responsiveness and proliferated to strikingly higher frequencies in mice bearing human lymphoma xenografts. NOTCH1-agonized CD4+ CAR-T also provided superior help to cotransferred CD8+ CAR-T, driving improved expansion and curative antitumor responses in vivo at low CAR-T doses. Our data expand the mechanisms by which NOTCH can shape CD4+ T-cell behavior and demonstrate that activating NOTCH1 signaling during genetic modification ex vivo is a potential strategy for enhancing the function of T cells engineered with tumor-targeting receptors. Ex vivo ligand-mediated activation of Notch signaling can be used to expand hematopoietic stem cells and immature T cells. Wilkens and colleagues apply these principles in creating a new system for the manufacture of Notch1-activated CD4+ CAR-T cells with enhanced cytokine production, expansion, helper T-cell function, and anticancer activity.