title: Retinoids and myelomonocytic growth factors cooperatively activate RARA and induce human myeloid leukemia cell differentiation via MAP kinase pathways.
abstract: Use of all-trans-retinoic acid (ATRA) in combinatorial differentiation therapy of acute promyelocytic leukemia (APL) results in exceptional cure rates. However, potent cell differentiation effects of ATRA are so far largely restricted to this disease and long-term survival rates in non-APL acute myelogeneous leukemia (AML) remain unacceptably poor, requiring development of novel therapeutic strategies. We demonstrate here that myelomonocytic growth factors (granulocyte colony-stimulating factor [G-CSF] and/or granulocyte macrophage colony-stimulating factor [GM-CSF]) potentiate differentiation effects of ATRA in different AML cell lines and primary cells from patients with myeloid leukemia. The ligand-dependent activities of endogenous and transiently expressed retinoic acid receptor alpha (RARalpha) isoforms can be potentiated by G/GM-CSF in U-937 cells and correlate with increased expression of ATRA-inducible RARalpha2 isoform. Specific inhibitors of mitogen mitogen-activated protein kinase (MAPK) (MEK)-1/-2 or p38 extracellular signal-related kinase (ERK) kinase diminish the ATRA as well as ATRA and G/GM-CSF-induced activation of the RARalpha proteins and decreased the differentiation-induced decline in cell numbers. Our data demonstrate that acting, at least in part, via the MAP kinase pathways, myelomonocytic growth factors enhance ATRA-dependent activation of the RARalpha isoforms and maturation of myeloid leukemia cells. These results suggest that combinatorial use of these agents may be effective in differentiation therapy of AML.
authors.affiliation: Section of Hematological Oncology, Institute of Cancer Research, London, United Kingdom.
authors.forename: Annegret
authors.initials: A
authors.lastname: Glasow
authors.forename: Natalia
authors.initials: N
authors.lastname: Prodromou
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.forename: Marieke
authors.initials: M
authors.lastname: von Lindern
authors.forename: Arthur
authors.initials: A
authors.lastname: Zelent
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D007951:Leukemia, Myeloid / Q000378:metabolism* / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements / Q000235:genetics; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D020033:Protein Isoforms; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D016179:Granulocyte Colony-Stimulating Factor; D014212:Tretinoin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor