STAT5B and B-cell chronic lymphocytic leukemia: Interestingly, in addition to GOF mutations, mining of publicly available gene expression datasets also revealed significantly increased levels of STAT5B mRNA in patients with hematopoietic cancers of chronic lymphocytic leukemia (CLL), T-ALL, B-cell acute lymphoblastic leukemia (B-ALL), and adult T-cell leukemia/lymphoma (ATLL) origin (Fig. 1b).