Abstract
Background:
Antitumor effect of chimeric antigen receptor (CAR)-T cells against solid tumors is limited due to various factors, such as low infiltration rate, poor expansion capacity, and exhaustion of T cells within the tumor. NR4A transcription factors have been shown to play important roles in T-cell exhaustion in mice. However, the precise contribution of each NR4a factor to human T-cell differentiation remains to be clarified.
Methods:
In this study, we deleted NR4A family factors, NR4A1, NR4A2, and NR4A3, in human CAR-T cells recognizing human epidermal growth factor receptor type 2 (HER2) by using the CRISPR/Cas9 system. We induced T-cell exhaustion in these cells in vitro through repeated co-culturing of CAR-T cells with Her2+A549 lung adenocarcinoma cells and evaluated cell surface markers such as memory and exhaustion phenotypes, proliferative capacity, cytokine production and metabolic activity. We validated the antitumor toxicity of NR4A1/2/3 triple knockout (TKO) CAR-T cells in vivo by transferring CAR-T cells into A549 tumor-bearing immunodeficient mice.
Results:
Human NR4A-TKO CAR-T cells were resistant against exhaustion induced by repeated antigen stimulation in vitro, and maintained higher tumor-killing activity both in vitro and in vivo compared with control CAR-T cells. A comparison of the effectiveness of NR4A single, double, and TKOs demonstrated that triple KO was the most effective in avoiding exhaustion. Furthermore, a strong enhancement of antitumor effects by NR4A TKO was also observed in T cells from various donors including aged persons. Mechanistically, NR4A TKO CAR-T cells showed enhanced mitochondrial oxidative phosphorylation, therefore could persist for longer periods within the tumors.
Conclusions:
NR4A factors regulate CAR-T cell persistence and stemness through mitochondrial gene expression, therefore NR4A is a highly promising target for the generation of superior CAR-T cells against solid tumors.