Adoptive cell therapy with chimeric antigen receptor T (CAR-T) cells has revolutionized treatment of hematologic malignancies, yet its efficacy against solid tumors remains limited by poor persistence, exhaustion, and terminal differentiation. TET2, a key DNA demethylase, regulates CD8+ T cell differentiation, and its loss promotes stem-like memory features. IL-21 further supports T cell longevity by sustaining less-differentiated subsets. Here, we investigated the impact of TET2 deficiency on the memory function of CAR-T cells, together with the role of IL-21 in orchestrating T cell differentiation and effector functions. In repeated in vitro stimulation assays using Nalm-6-EGFRvIII or BT-474 tumor cells, IL-21-armored TET2 KO CAR-T cells maintained superior proliferation across four to six sequential tumor challenges, accompanied by reduced expression of exhaustion markers (e.g., PD-1 and TIM-3) and better preservation of a memory phenotype compared with wild-type CAR-T cells. In NSG mouse xenograft models of U87-EGFRvIII glioblastoma, IL-21–armored TET2 KO CAR-T cells achieved durable tumor regression and significantly prolonged survival, with tumor-infiltrating lymphocyte analysis revealing expansion of memory-like and progenitor-exhausted populations. To enable safer clinical translation, we further established a tamoxifen-inducible IL-21 (synZFTR) system that conferred comparable anti-tumor efficacy. Taken together, this intervention significantly enhances CAR-T survival, expansion, and maintenance of less-differentiated subtypes.
Collectively, these findings demonstrate that combining TET2 knockout with IL-21 armoring enhances CAR-T cell survival, expansion, and maintenance of less-differentiated states, thereby improving persistence and antitumor efficacy against solid tumors. This strategy may provide a promising platform for next-generation CAR-T cell therapies against solid tumors.