Jain et al. reported that SUV39H1 knockout in human CAR-T cells led to a slight reduction in the production of effector cytokines such as TNFα, IFNγ, IL2 and granzyme B. However, after multiple rounds of tumor cell co-culture, SUV KO 1928z CAR-T cells exhibited enhanced mitochondrial activity and improved metabolic fitness, while maintaining chromatin accessibility at loci (KLF2, LEF1, TCF7) associated with T cell memory and effector functionality and decreasing accessibility at effector function and immune checkpoint gene loci. Here, IL2 is linked to neoplasm.