STAT5BN642H is a driver mutation for T cell neoplasia.

STAT5B is often mutated in hematopoietic malignancies. The most frequent STAT5B mutation, Asp642His (N642H), has been found in over 90 leukemia and lymphoma patients. Here, we used the Vav1 promoter to generate transgenic mouse models that expressed either human STAT5B or STAT5B(N642H) in the hematopoietic compartment. While STAT5B-expressing mice lacked a hematopoietic phenotype, the STAT5B(N642H)-expressing mice rapidly developed T cell neoplasms. Neoplasia manifested as transplantable CD8(+) lymphoma or leukemia, indicating that the STAT5B(N642H) mutation drives cancer development. Persistent and enhanced levels of STAT5B(N642H) tyrosine phosphorylation in transformed CD8(+) T cells led to profound changes in gene expression that were accompanied by alterations in DNA methylation at potential histone methyltransferase EZH2-binding sites. Aurora kinase genes were enriched in STAT5B(N642H)-expressing CD8(+) T cells, which were exquisitely sensitive to JAK and Aurora kinase inhibitors. Together, our data suggest that JAK and Aurora kinase inhibitors should be further explored as potential therapeutics for lymphoma and leukemia patients with the STAT5B(N642H) mutation who respond poorly to conventional chemotherapy.