STAT5B and acute myeloid leukemia: While the constitutve STAT5 phosphorylation in AML 2007-272 was readily detected by Western blotting, the basal levels of pSTAT5 of AML 2003-119, 2003-114 and 2005-016 were not detected although constitutive levels were found in FACS analysis, reflecting a higher sensitivity of FACS compared Western blotting.