Regnase-1 limits formation of T_PEXCAR-T cells and reduces their memory phenotype. (A) Comparison of T_PEX-related gene expression in the presence vs absence of tumor in either WT (left) or KO (right) CAR-T cells. Cutoff FDR < 0.05 or log₂FC > 0.5. Data represent biological replicates of 4 to 5 mice per group. (B-E) CD8⁺ WT and KO CAR-T cells were cotransferred 1:1 into tumor-bearing mice. Organs were harvested 7 and 21 days later. (B) Frequencies of TCF-1⁺ WT and KO CAR-T cells. (C) Mean fluorescence intensity (MFI) of TOX in TCF-1⁺ WT and KO CAR-T cells. (D) Frequencies of TCF-1⁺CD127⁺KLRG1⁻ and TCF-1⁺CD127⁻KLRG1⁺ WT and KO CAR-T cells. (E) Frequencies of TCF-1⁺IFNγ⁺, TCF-1⁺IL-2⁺, TCF-1⁺TNFα⁺, or TCF-1⁺granzyme B⁺ WT and KO CAR-T cells. (F) CD8⁺ WT and KO CAR-T cells were cotransferred 1:1 into tumor-bearing mice and sorted from spleens 21 days later. Sorted cells (>90% TCF-1⁺) were cotransferred 1:1 into naive recipients that received hCD19⁺ B-ALL cells the following day. Spleens were harvested 5 days later. Frequencies of TCF-1⁺ WT and KO CAR-T cells 21 days after primary tumor stimulation (left) and 5 days after secondary cotransfer and tumor stimulation (right). Data are shown as mean plus or minus SEM and represent 2 independent experiments (B-F; n = 3-5 mice per group). Significance was determined by the paired Student t test (B-F). *P < .05; **P < .01; ***P < .001; ****P < .0001.