All animal procedures were approved by the Shanghai LIDE Institutional Animal Care and Use Committee and performed following the principles and procedures of the Association for Assessment and Accreditation of Laboratory Animal Care International. One week before transplant, 6- to 8-week-old NCG mice were given 0.2 mg/50 µL busulfan daily for 2 days by intraperitoneal injection. Then they were injected intrafemorally with 1–2×10⁶ peripheral blood or bone marrow cells of AML or ALL patients after being anesthetized with a 1.25% avertin solution.