AUTHOR=Harrer Dennis Christoph , Bezler Valerie , Hartley Jordan , Herr Wolfgang , Abken Hinrich 

TITLE=IRF4 downregulation improves sensitivity and endurance of CAR T cell functional capacities

JOURNAL=Frontiers in Immunology

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1185618

DOI=10.3389/fimmu.2023.1185618

ISSN=1664-3224

ABSTRACT=Chimeric antigen receptor (CAR) modified T cells can induce complete remissions in patients with advanced hematological malignancies, however, the efficacy is mostly transient and remains so far poor in the treatment of solid tumors. Crucial barriers to long-term CAR T cell success encompass loss of functional capacities summarized as “exhaustion”, among others. To extend CAR T cell functionality, we down-tuned interferon regulatory factor-4 (IRF4) levels in CAR T cells using a one-vector system encoding a specific short-hairpin (sh) RNA along with constitutive CAR expression. At baseline, CAR T cells with downregulated IRF4 showed equal cytotoxicity and cytokine release compared to conventional CAR T cells. However, under conditions of repetitive antigen encounter, IRF4low CAR T cells displayed enhanced functionality with superior cancer cell control in the long-term compared with conventional CAR T cells. Mechanistically, down-tuning IRF4 in CAR T cells resulted in memory-like capacities and prolonged functional capacities through upregulated CD27. Moreover, IRF4low CAR T cells were more sensitive to cancer cells with low levels of target antigen. Overall, IRF4 downmodulation enables CAR T cells to recognize and respond to target cells with improved sensitivity and endurance.