To test the exclusive specificity to the mutants, we cocultured 806 and 2173 CAR T cells with the CML cell line K562, transduced to express wtEGFR, EGFRvIII, or EGFR mutants, as K562 does not have any endogenous EGFR (Figure 2B). Here, EGFR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.