After inoculation of 10 × 103 ALL cells, 2.5 × 106 STAT3–/– T cells were enough to prevent tumor growth in all (9/9) recipients, while all (9/9) recipients given TCD-BM alone had progressive tumor growth and died by 15 days after HCT (Figure 2, E and F). Here, STAT3 is linked to acute lymphoblastic leukemia.