CISH and leukemia: The first group is believed to be more involved in regulation of cytokine receptor signaling via the JAK-STAT signaling pathway while SOCS4-7 are suggested to function primarily in growth factor receptor signaling.[18] Since SOCS1 exerted a very potent inhibition of the IL-3 dependent proliferation of Ba/F3 cells compared to CIS and SOCS2 (Fig 3A), we focused our efforts on the role of SOCS1 in BCR-ABL induced transformation and leukemia.