BACH2 dosage establishes the hierarchy of stemness and finetunes antitumor immunity in CAR T cells 2256626

Abstract

Abstract Introduction Self-renewing stem-like T cells promote the efficacy of cancer immunotherapy and are a heterogeneous population with sub-lineages demonstrating different degrees of stemness. At the apex of this hierarchy are long-term (LT) stem-like T cells with the highest capacity of persistence, repopulation and response to immune checkpoint inhibitors (ICI). However, the pathway that establishes the hierarchy of stemness in chimeric antigen receptor (CAR) T cells and its role in anti-tumor efficacy of CAR T cells are unclear. Methods We analyzed CAR T cell infusion products from both humans and mice, examining epigenetic, transcriptional, and functional correlates of stem-like subsets. We deleted BACH2 to assess its role in LT stem-like differentiation and antitumor potency. In a GD2 CAR T model prone to exhaustion, we used small-molecule modulation to fine-tune BACH2 protein levels and temporally activate BACH2 during CAR T manufacture, followed by in vivo efficacy testing in solid tumor models. Results We demonstrate that BACH2 regulates LT stem-like CAR T cell differentiation and antitumor immunity in a dose-dependent manner. Pre-infusion LT stem-like CAR T cells displayed epigenetic activation of BACH2 and correlated with more robust antitumor responses in both mice and humans. After tumor clearance in vivo, LT stem-like cells emerged that transcriptionally and epigenetically upregulated BACH2 and downregulated TOX. Loss of BACH2 impaired antitumor efficacy and disrupted the LT stem-like transcriptional program. In GD2 CAR T cells, quantitative control of BACH2 via a small molecule adjusted the balance between stemness and exhaustion. Temporal induction of BACH2 during CAR T manufacturing enhanced antitumor immunity in solid tumor models compared to unmodified cells. Conclusion Together, we show that BACH2 dosage establishes the hierarchy of stem-like CAR T cells and can be temporally and tunably controlled in CAR T cells to optimize differentiation and antitumor immunity. Funding Source AI154450 from National Institutes of Health, RR210035 from Cancer Prevention and Research Institute of Texas, HT94252310801 from Department of Defense to C. Yao; AI158294, AG083398, AG056524 from National Institutes of Health, Clinic & Laboratory Integrat Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)