STAT5 in B cell development and leukemia

Early B cell development depends on a network of transcription factors, whereby E2A and EBF1 regulate B cell specification and Pax5 controls B-lineage commitment. In contrast, activation of the transcription factor STAT5 in response to IL-7R signaling promotes cell survival by activating the prosurvival gene Mcl1 and orders immunoglobulin gene rearrangement by repressing Igk recombination in pro-B cells. Subsequently, it cooperates with the pre-B cell receptor to facilitate pre-B cell expansion. STAT5 also plays a key role in the generation of B cell precursor acute lymphoblastic leukemia, whereby the BCR-ABL1 translocation or the collaboration of JAK2 mutations with overexpression of the thymic stromal lymphopoietin receptor CRLF2 results in constitutive STAT5 activation leading to cytokine-independent survival and growth of leukemic cells.