Moreover, our finding also provides an explanation for the observation that constitutive STAT5 activation coincides with functional loss of p53 in B-cell lymphoma/leukemia.30 It was also demonstrated that knockdown of STAT5A in CML hematopoietic progenitors could dramatically increase the p53 expression level,29 which is in line with our data. Here, STAT5B is linked to leukemia.