Novel activating STAT5B mutations as putative drivers of T-cell acute lymphoblastic leukemia

STAT5 has an important role in many hematologic malignancies, but constitutive activation is often a secondary event.1 Mutations to STAT5B and their functional significance were recently discovered in large granular lymphocytic (LGL) leukemia.2 The mutations located in the SRC homology 2 (SH2) domain of STAT5B lead to constitutive phosphorylation of the mutant protein, increased transcriptional activity and activation of downstream target genes. However, activating mutations in STAT5B have thus far not been described in other cancers.