Whilst we had shown that the expression of EphA2 is not essential for normal hematopoiesis, the increased expression of this gene in MLL transfected K562 cells and interaction of Eph tyrosine kinases with the Abl/Arg tyrosine kinase raised the possibility that EphA2 might be functionally important in MLL and/or BCR-ABL type leukemias [16, 21]. This evidence concerns the gene ABL1 and leukemia.