AZ960, a novel Jak2 inhibitor, induces growth arrest and apoptosis in adult T-cell leukemia cells

Adult T-cell leukemia/lymphoma (ATL) is a highly aggressive disease in which the JAK2/STAT5 pathway is constitutively activated. This study found that AZ960, a novel inhibitor of JAK2 kinase, effectively induced growth arrest and Apoptosis of human T-cell lymphotropic virus type 1, HTLV-1-infected T cells (MT-1 and MT-2) in parallel with downregulation of the phosphorylated forms of JAK2 and Bcl-2 Family proteins including Bcl-2 and Mcl-1. Interestingly, AZ960 increased levels of Bcl-xL in MT-1 and MT-2 cells in association with accumulation of cAMP response element-binding protein bound to the Bcl-xL promoter as measured by chromatin immunoprecipitation assay. Importantly, genetic inhibition of Bcl-xL by a small interfering RNA potentiated antiproliferative effects of AZ960 in MT-1 cells. Taken together, JAK2 is an attractive molecular target for treatment of ATL. Concomitant blockade of JAK2 and Bcl-xL may be a promising treatment strategy for this lethal disease.