SUV39H1 Ablation Enhances Long-Term CAR-T Function in Solid Tumors

Abstract Failure of adoptive T-cell therapies in patients with cancer is linked to limited T-cell expansion and persistence, even in memory-prone 41BB-(BBz)–based chimeric antigen receptor (CAR) T cells. We show here that BBz-CAR T-cell stem/memory differentiation and persistence can be enhanced through epigenetic manipulation of the histone 3 lysine 9 trimethylation (H3K9me3) pathway. Inactivation of the H3K9 trimethyltransferase SUV39H1 enhances BBz-CAR T cell long-term persistence, protecting mice against tumor relapses and rechallenges in lung and disseminated solid tumor models up to several months after CAR T-cell infusion. Single-cell transcriptomic (single-cell RNA sequencing) and chromatin opening (single-cell assay for transposase accessible chromatin) analyses of tumor-infiltrating CAR T cells show early reprogramming into self-renewing, stemlike populations with decreased expression of dysfunction genes in all T-cell subpopulations. Therefore, epigenetic manipulation of H3K9 methylation by SUV39H1 optimizes the long-term functional persistence of BBz-CAR T cells, limiting relapses, and providing protection against tumor rechallenges. Significance: Limited CAR T-cell expansion and persistence hinders therapeutic responses in solid cancer patients. We show that targeting SUV39H1 histone methyltransferase enhances 41BB-based CAR T-cell long-term protection against tumor relapses and rechallenges by increasing stemness/memory differentiation. This opens a safe path to enhancing adoptive cell therapies for solid tumors. See related article by Jain et al., p. 142.