title: Inhibition of p38 MAP kinase activity up-regulates multiple MAP kinase pathways and potentiates 1,25-dihydroxyvitamin D(3)-induced differentiation of human leukemia HL60 cells.
abstract: Differentiation therapy for neoplastic diseases has potential for supplementing existing treatment modalities but its implementation has been slow. One of the reasons is the lack of full understanding of the complexities of cellular pathways through which signals for differentiation lead to cell maturation. This was addressed in this study using HL60 cells, a well-established model of differentiation of neoplastic cells. SB 203580 and SB 202190, specific inhibitors of a signaling protein p38 MAP kinase, were found to markedly accelerate monocytic differentiation of HL60 cells induced by low concentrations of 1,25-dihydroxyvitamin D(3) (1,25D(3)). Surprisingly, inhibition of p38 activity resulted in sustained enhancement of p38 phosphorylation and of its in vitro activity in the absence of the inhibitor, indicating up-regulation of the upstream components of the p38 pathway. In addition, SB 203580 or SB 202190 treatment of HL60 cells resulted in a prolonged activation of the JNK and, to a lesser extent, the ERK pathways. The data are consistent with the hypothesis that in HL60 cells an interruption of a negative feedback loop from a p38 target activates a common regulator of multiple MAPK pathways. The possibility also exists that JNK and/or ERK pathways amplify a differentiation signal provided by 1,25D(3).
authors.affiliation: Department of Pathology and Laboratory Medicine, UMD-New Jersey Medical School, 185 S. Orange Avenue, Newark, New Jersey 07103, USA.
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: J
authors.initials: J
authors.lastname: Rao
authors.forename: G P
authors.initials: GP
authors.lastname: Studzinski
mesh_terms: D002117:Calcitriol / Q000378:metabolism / Q000494:pharmacology*; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D016196:S Phase; D013997:Time Factors; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D048056:Mitogen-Activated Protein Kinase 9; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002117:Calcitriol; C093642:SB 203580; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole