Growth autonomy and lineage switching in BCR-ABL-transduced human cord blood cells depend on different functional domains of BCR-ABL.

The tyrosine kinase activity of p210BCR-ABL is essential to its leukemogenic potential, but the role of other functional domains in primary human hematopoietic cells has not been previously investigated. Here we show that infection of normal human CD34+ cord blood (CB) cells with a retroviral vector encoding p210BCR-ABL rapidly activates a factor-independent phenotype and autocrine interleukin-3/granulocyte colony-stimulating factor/erythropoietin production in the transduced cells. These changes are characteristic of primitive chronic myeloid leukemic (CML) cells and are important to the leukemogenicity of BCR-ABL-transduced murine hematopoietic stem cells. When BCR-ABL-transduced human CB cells were incubated with imatinib mesylate, an inhibitor of the p210BCR-ABL kinase, or when human CB cells were transduced with a BCR-ABL cDNA lacking the SH2 domain (p210DeltaSH2), factor independence was significantly reduced. In contrast, deletion of the SH2 domain had little impact on the p210BCR-ABL kinase-dependent promotion of erythropoietic differentiation also seen immediately following the BCR-ABL transduction of primitive human CB cells, but not in naturally occurring CML. Thus, p210BCR-ABL has distinct biological effects in primary human hematopoietic cells, which variably mimic features of human CML, and activation of these changes can show different dependencies on the integrity of the SH1 and SH2 domains of p210BCR-ABL.