NSG-AML samples express MLL-AFX1 mRNA. (A) Surface-marker expression in NSG-engrafting AML (blue), engrafting AML (green), and nonengrafting AML (red) samples. Percentage of positive population by flow cytometry is represented. NSG-AML: AML#22, #23, #24. AML: AML#1, #2, #3, #4, #5, #6, #8, #9, #11, #20, #21. Nonengrafting AML: AML#26, #27, #29, #37, #38, #39, #41, #42, #43, #44. *P ≤ .05. (B) Surface-marker expression in CD34-positive NSG-AML (blue), AML (green), and nonengrafting AML (red) samples analyzed as in panel A. (C) mRNA from de novo and engrafted samples was isolated and RT-PCR against MLL fusion proteins was performed.