CD8A and breast cancer: Strikingly, progenitor-exhausted–like (Tpex-like) cells among CD4+ and CD8+ populations (TCF7highCCR7highTOX2highKLF2low) were markedly enriched in MGA271 and Hu8H9 CAR-T cells compared with B7H3.BC CAR-T cells (Figure 4E; Figure S11B), suggesting that high tonic-signaling MGA271 and Hu8H9 CAR-T cells are more prone to entering a progenitor-exhaustion state than B7H3.BC CAR-T cells.