title: Down-regulation of interleukin-3/granulocyte-macrophage colony-stimulating factor receptor beta-chain in BCR-ABL(+) human leukemic cells: association with loss of cytokine-mediated Stat-5 activation and protection from apoptosis after BCR-ABL inhibition.
abstract: Several signaling cascades are engaged by expression of the p210 bcr-abl tyrosine kinase, and evidence suggests that these signals drive leukemogenesis. In this report, signaling pathways were examined and compared between cells derived from leukemic patients and cells expressing a bcr-abl construct (MBA). The effects of acute inhibition of bcr-abl with STI-571 on these signals and the survival of bcr-abl-expressing cells were also evaluated. Expression of bcr-abl in interleukin-3 (IL-3)/granulocyte-macrophage colony-stimulating factor (GM-CSF)-dependent Mo7e cells (MBA) resulted in growth factor independence, constitutive activation of Stat-5 phosphorylation, engagement of mitogen-activated protein (MAP) kinase signals, and increased expression of PTP1B and bcl-x(L). STI-571 inhibited cell growth and induced apoptosis in bcr-abl-expressing cells (MBA, K562, BV-173, KBM5) but not in bcr-abl(-) tumor cells (Mo7e, KG-1, ME-180, Daudi). STI-571-mediated apoptosis correlated with the inhibition of Stat-5 and MAP kinase activation and a reduction in overexpressed bcl-x(L) but not in PTP1B. Inhibitor had no effect on IL-3/GM-CSF-dependent Mo7e cell signaling and did not prevent activation of the other Jak/Stat pathways (interferon alpha, IL-3/GM-CSF). However, neither IL-3 nor GM-CSF could reactivate Stat-5 after the STI-571-mediated inhibition of bcr-abl. Expression of the common beta-chain of the IL-3/GM-CSF receptor was down-regulated in Stat-5-activated myeloid leukemic cells, suppressing IL-3/GM-CSF signal transduction and the ability of these cytokines to provide apoptotic protection. These studies suggest that bcr-abl activates cytokine-independent mechanisms of survival while inactivating intrinsic cytokine signaling cascades, making bcr-abl(+) myeloid cells vulnerable to apoptosis after bcr-abl inactivation.
authors: Department of Bioimmunotherapy, M. D. Anderson Cancer Center, University of Texas, Houston 77030, USA. ndonato@mdanderson.org
authors: N J
authors: NJ
authors: Donato
authors: J Y
authors: JY
authors: Wu
authors: L
authors: L
authors: Zhang
authors: H
authors: H
authors: Kantarjian
authors: M
authors: M
authors: Talpaz
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D015536:Down-Regulation; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000235:genetics*; D006801:Humans; D007938:Leukemia / Q000235:genetics* / Q000473:pathology*; D008894:Milk Proteins; D016185:Receptors, Interleukin-3 / Q000235:genetics*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D008894:Milk Proteins; D016185:Receptors, Interleukin-3; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D016044:Fusion Proteins, bcr-abl