IRF8 and myeloid leukemia: To test this hypothesis, we transfected U937 myeloid leukemia cells with a 130 bp GAS2 promoter/reporter construct (including an Icsbp-binding cis element) and various combinations of vectors to express Bcr-abl, Icsbp, a tyrosine mutant form of Icsbp (Y-mut Icsbp), or a dominant negative form of Shp2 (C463S) (or relevant control vectors).