Normal ABL1 kinase plays a tumor suppressor role in BCR-ABL1–induced leukemogenesis. BCR-ABL1 Abl1−/− [−/−], BCR-ABL1 Abl1+/+ [+/+], and BCR-ABL1 Abl1−/− leukemia cells reconstituted with YFP-ABL1 [−/−(+)] were inoculated IV into NOD/SCID mice. Kaplan-Meier survival curve of mice injected with (A) 103 freshly transfected cells [(−/−) and (+/+): n = 8] and (B) 103 [(+/+): n = 6, (−/−) and (−/−)+: n = 12] or (C) 105 [(−/−): n = 13, (+/+) and (−/−)+: n = 12] 5-week-old tissue-cultured cells; n = number of mice per group.