title: Tyrosine kinase inhibitor STI571 potentiates the pharmacologic activity of retinoic acid in acute promyelocytic leukemia cells: effects on the degradation of RARalpha and PML-RARalpha.
abstract: The 2-phenylaminopyrimidine derivative STI571 is a selective inhibitor of c-Abl, c-kit, and platelet-derived growth factor-receptor tyrosine kinases and is presently in phase II-III clinical studies. Here, this study reports on a novel pharmacologic activity of the compound, ie, enhancement of the cyto-differentiating, growth-inhibitory, and apoptogenic actions of all-trans-retinoic acid (ATRA). Whereas STI571 is not a cytodifferentiating agent by itself, the compound interacts with ATRA and enhances the myeloid maturation program set in motion by the retinoid in the PML-RARalpha(+) acute promyelocytic leukemia NB4 and the PML-RARalpha(-) myeloblastic HL60 and U937 cell lines. In addition, STI571 relieves the cyto-differentiation block observed in the ATRA-resistant cell lines, NB4.R1, NB4.306, and NB4.007. In NB4 promyelocytes, a RARalpha agonist, but not an RXR agonist, can substitute for ATRA and interact with STI571. By contrast, STI571 is unique among c-Abl-specific tyrosine kinase inhibitors in modulating the pharmacologic activity of ATRA. In NB4 cells, enhanced cyto-differentiation results in increased up-regulation of the expression of a number of genes coding for myeloid differentiation markers, including CD11b, CD11c, and some of the components of the nicotinamide adenine dinucleotide phosphate-oxidase enzymatic complex. All this is accompanied by inhibition of c-Abl tyrosine phosphorylation and retardation of the retinoid-dependent degradation of PML-RARalpha and RARalpha. Stabilization of the 2 retinoic acid receptors is likely to be the result of augmented and accelerated inhibition of the proteasome-dependent proteolytic activity observed on ATRA treatment.
authors.affiliation: Divisione di Ematologia, Ospedali Riuniti di Bergamo, Bergamo, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Gianni'
authors.forename: Y
authors.initials: Y
authors.lastname: Kalaç
authors.forename: I
authors.initials: I
authors.lastname: Ponzanelli
authors.forename: A
authors.initials: A
authors.lastname: Rambaldi
authors.forename: M
authors.initials: M
authors.lastname: Terao
authors.forename: E
authors.initials: E
authors.lastname: Garattini
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D018845:CD11 Antigens / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006098:Granulocytes / Q000473:pathology; D018922:HL-60 Cells; D006801:Humans; D000068877:Imatinib Mesylate; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism* / Q000473:pathology; D010879:Piperazines / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011743:Pyrimidines / Q000494:pharmacology*; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D020298:U937 Cells
chemical_list: D001549:Benzamides; D018845:CD11 Antigens; D004791:Enzyme Inhibitors; D010879:Piperazines; D011743:Pyrimidines; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D014157:Transcription Factors; D014212:Tretinoin; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases