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

Abstract

Chimeric antigen receptor (CAR) modified T cells can induce complete remissions in patients with advanced hematological malignancies. Nevertheless, 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 known as “exhaustion”, among others. To extend CAR T cell functionality, we reduced 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, the downregulation of IRF4 in CAR T cells resulted in prolonged functional capacities and upregulation of CD27. Moreover, IRF4low CAR T cells were more sensitive to cancer cells with low levels of target antigen. Overall, IRF4 downregulation capacitates CAR T cells to recognize and respond to target cells with improved sensitivity and endurance.

A Review of CAR-T Combination Therapies for Treatment of Gynecological Cancers

“…The hypoxic and acidic conditions within solid tumors also negatively impact the functionality of CAR-T cells, contributing to their rapid exhaustion [ 12 ]. Numerous studies have also highlighted the role of multiple transcription factors as contributors to CAR-T cell exhaustion within solid tumors; these factors include Thymocyte selection-associated high mobility group box protein (TOX), interferon regulatory factor (IRF4), Nuclear factor of activated T cells (NFATs), and Myeloblastosis transcription factors (MYBs) [ 13 , 14 , 15 , 16 ]. In addition, not only long-term resistance but also short-term tumor adaptation to CAR is a problem.…”

Fine-tuning the antigen sensitivity of CAR T cells: emerging strategies and current challenges

“…Recently, we reported that downregulation of the transcription factor interferon regulatory factor-4 (IRF4) improved antigen sensitivity which enabled CAR T cells to target antigen low pancreatic cancer cells that are not recognized by CAR T cells with physiological IRF4 levels ( 48 ). IRF4 downregulation provoked an overall increase in T cell activation in response to antigen low pancreatic cancer cells reflected by the upregulation of members of the IL-2 signaling pathway, such as CD25 and phospho-STAT5 ( 48 ).…”

“…Recently, we reported that downregulation of the transcription factor interferon regulatory factor-4 (IRF4) improved antigen sensitivity which enabled CAR T cells to target antigen low pancreatic cancer cells that are not recognized by CAR T cells with physiological IRF4 levels ( 48 ). IRF4 downregulation provoked an overall increase in T cell activation in response to antigen low pancreatic cancer cells reflected by the upregulation of members of the IL-2 signaling pathway, such as CD25 and phospho-STAT5 ( 48 ). We hypothesized that a direct increase in c-Jun-mediated transcriptional activation of target genes, such as IL-2, through displacing AP1-IRF4 complexes from chromatin is likely the driving factor, similar to the effects obtained by c-Jun overexpression.…”