Menendez et al. documented that BM-derived MSCs from infants with MLL-AF4+ acute leukemia harbor and express the MLL-AF4 fusion gene, while they did not find fusion genes in BM-MSCs of childhood leukemias carrying TEL-AML1, BCR-ABL, AML1-ETO, MLL-AF9, MLL-AF10, MLL-ENL translocations or hyperdiploidy. Here, AFF1 is linked to acute leukemia.