erbstatin and Leukemia--Promyelocytic--Acute

Leukocyte alkaline phosphatase (LAP) is synergistically induced by the combination of all-trans retinoic acid (ATRA) and granulocyte-colony-stimulating factor (G-CSF) in acute promyelocytic leukemia (APL) cells (Gianni' M. et al., Blood 83: 1909-1921, 1994). The role of cAMP and tyrosine kinases in the induction of LAP was investigated. In the APL cell line NB4, adenosine-3': 5'-monophosphothioate, cyclic, Rp isomer, a reversible inhibitor of cAMP-dependent protein kinase (PKA), has no effect on the induction of LAP enzymatic activity and mRNA triggered by ATRA+G-CSF, in conditions where this compound completely blocks the upregulation of LAP transcript caused by the combination of the PKA agonist, dibutyryl-cAMP (db-cAMP), and ATRA. Challenge of NB4 cells with G-CSF, dbcAMP and ATRA causes a much higher induction of LAP relative to that observed in the presence of ATRA+G-CSF or ATRA+dbcAMP. Treatment of NB4 with ATRA and G-CSF results in increases in the tyrosine phosphorylation of several proteins. In the presence of the cytokine and the retinoid, tyrosine kinase inhibitors decrease LAP enzymatic activity and mRNA.

Topics: Alkaline Phosphatase; Bucladesine; Cyclic AMP-Dependent Protein Kinases; Enzyme Activation; Enzyme Induction; Gene Expression Regulation, Neoplastic; Genistein; Granulocyte Colony-Stimulating Factor; Humans; Hydroquinones; In Vitro Techniques; Isoflavones; Leukemia, Promyelocytic, Acute; Protein-Tyrosine Kinases; Receptors, Granulocyte Colony-Stimulating Factor; RNA, Neoplasm; Tretinoin; Tumor Cells, Cultured

Receptors of the hematopoietin superfamily, including the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor, lack a tyrosine kinase domain as well as other sequences indicative of a known signaling mechanism. In this report, we identify the serine/threonine kinase, microtubule-associated protein 2 (MAP2) kinase, as an intermediate in the GM-CSF signal transduction pathway. Treatment of peripheral blood neutrophils or terminally differentiated HL-60 cells with GM-CSF induced a rapid and dose-dependent increase in MAP2 kinase activity. Maximal activity occurred within 5 minutes and the kinetics of the response varied depending on the target cell (prolonged in neutrophils and transient in neutrophilic HL-60 cells). MAP2 kinase activity in these cells correlates with the induction of a 42-Kd tyrosine phosphoprotein. Furthermore, tyrosine phosphorylation is necessary for MAP2 kinase activation since its activity is inhibited by treatment with the tyrosine kinase inhibitor, erbstatin analog. These data suggest that tyrosine phosphorylation is important in GM-CSF-mediated signal transduction and that MAP2 kinase activation may be a central biochemical event involved in its signaling.

Topics: Calcium-Calmodulin-Dependent Protein Kinases; Enzyme Activation; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Hydroquinones; Kinetics; Leukemia, Promyelocytic, Acute; Neutrophils; Phosphorylation; Protein Kinase Inhibitors; Protein Kinases; Protein-Tyrosine Kinases; Signal Transduction; Tumor Cells, Cultured; Tyrosine