title: Daphnetin induced differentiation of human renal carcinoma cells and its mediation by p38 mitogen-activated protein kinase.
abstract: Daphnetin has been shown to be a potent in vitro anti-proliferative agent to the human renal cell carcinoma (RCC) cell line, A-498. In the present study, we investigated its effects on mitogen-activated protein kinase (MAPK) signalling along with cell cycle events and cellular differentiation. Daphnetin-activated p38, however, higher concentrations were required to inhibit ERK1/ERK2. In addition, it did not activate SAPK or induce apoptosis, but instead inhibited S phase cell cycle transition of A-498 cells at low concentrations and time of exposure. In addition, a late G(1), early S phase inhibition was observed at higher concentrations and time of exposure, indicating that the mechanism of daphnetin-induced differentiation was concentration dependent. Increased expression of the epithelial differentiation markers cytokeratins 8 and 18, correlated with increasing concentrations of daphnetin, while pre-treatment with a specific p38-inhibitor, served to limit this effect. There was no evidence that P-glycoprotein (P-gp) mediated multi-drug resistance (MDR) played a role in the anti-proliferative activity of daphnetin. Consequently, we concluded that p38 MAP kinase is intrinsically involved in mediating the effect of daphnetin in A-498 cells, suggesting that this drug may act by promotion of cellular maturation, and consequently may represent a novel low toxic approach for the treatment of poorly differentiated RCCs.
authors.affiliation: Department of Applied Science, National Centre for Sensor Research, School of Science, Institute of Technology, Tallaght, Dublin 24, Ireland.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Finn
authors.forename: Bernadette S
authors.initials: BS
authors.lastname: Creaven
authors.forename: Denise A
authors.initials: DA
authors.lastname: Egan
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D018432:Drug Resistance, Multiple / Q000187:drug effects; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D014407:Tumor Cells, Cultured; D014468:Umbelliferones / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D014468:Umbelliferones; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C039952:daphnetin