Transformation capacity of MLL-Af4 is compromised in the myeloid microenvironment. (A) Schematic of experiment. (B) Growth curve of human HSPCs expressing MLL-AF9/MLL-Af4 in myeloid culture. One representative experiment of 3 is shown. (C) Flow cytometry analysis of cell surface marker of week 5 myeloid cultures. (D) Survival curve of primary NSGS mice received MLL-AF9/MLL-Af4 cells. The BM of the remaining living Af4 mice was examined at day 150 and showed ALL. Five independent experiments were included. (E) Cell surface maker analysis by flow cytometry of BM from MLL-AF9/MLL-Af4 primary NSGS mice developing myeloid disease. (F) Wright-Giemsa–stained BM cytospins of primary mice. The images were obtained using a Motic BA310 microscope with ×40 objective. Scale bar, 10 µm. (G) Flow cytometry analysis of BM from MLL-Af4 primary NSGS mice developing lymphoid disease. (H) Survival curve of secondary NSGS mice receiving primary myeloid disease. The BM of the remaining living Af4 mice was examined at day 150 and showed ALL or no human engraftment. Five independent experiments were included. (I) Representative flow cytometry analysis of BM from secondary recipients. P values were calculated using the log-rank test (see also supplemental Table 1). hCD45, human CD45; mCD45, murine CD45.