CXCR4 and acute myeloid leukemia: On the contrary, a subsequent study by Ramakrishnan et al. demonstrated the dispensability of CXCR4 in BM homing of stem-cell enriched MLL-AF9 AML cells in sub-lethally irradiated mice, despite the critical need of CXCR4 for growth by AML cells in said model [67].