title: Constitutive Smad linker phosphorylation in melanoma: a mechanism of resistance to transforming growth factor-β-mediated growth inhibition.
abstract: Melanoma cells are resistant to transforming growth factor-β (TGFβ)-induced cell-cycle arrest. In this study, we investigated a mechanism of resistance involving a regulatory domain, called linker region, in Smad2 and Smad3, main downstream effectors of TGFβ. Melanoma cells in culture and tumor samples exhibited constitutive Smad2 and Smad3 linker phosphorylation. Treatment of melanoma cells with the MEK1/2 inhibitor, U0126, or the two pan-CDK and GSK3 inhibitors, Flavopiridol and R547, resulted in decreased linker phosphorylation of Smad2 and Smad3. Overexpression of the linker phosphorylation-resistant Smad3 EPSM mutant in melanoma cells resulted in an increase in expression of p15(INK4B) and p21(WAF1) , as compared with cells transfected with wild-type (WT) Smad3. In addition, the cell numbers of EPSM Smad3-expressing melanoma cells were significantly reduced compared with WT Smad3-expressing cells. These results suggest that the linker phosphorylation of Smad3 contributes to the resistance of melanoma cells to TGFβ-mediated growth inhibition.
authors.affiliation: Department of Medicine, Division of Medical Oncology, UMDNJ-Robert Wood Johnson Medical School, the Cancer Institute of New Jersey, New Brunswick, NJ, USA. cohenska@umdnj.edu
authors.forename: Karine A
authors.initials: KA
authors.lastname: Cohen-Solal
authors.forename: Kim T
authors.initials: KT
authors.lastname: Merrigan
authors.forename: Joseph L-K
authors.initials: JL
authors.lastname: Chan
authors.forename: James S
authors.initials: JS
authors.lastname: Goydos
authors.forename: Wenjin
authors.initials: W
authors.lastname: Chen
authors.forename: David J
authors.initials: DJ
authors.lastname: Foran
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Ahmed
authors.initials: A
authors.lastname: Lasfar
authors.forename: Michael
authors.initials: M
authors.lastname: Reiss
mesh_terms: D045744:Cell Line, Tumor; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D010880:Piperidines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011743:Pyrimidines / Q000494:pharmacology; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: C515235:(4-amino-2-(1-methanesulfonylpiperidin-4-ylamino)pyrimidin-5-yl)(2,3-difluoro-6-methoxyphenyl)methanone; C493956:CDKN1A protein, human; C493966:CDKN2B protein, human; D050762:Cyclin-Dependent Kinase Inhibitor p15; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005419:Flavonoids; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; C077990:alvocidib; C482128:MAP2K2 protein, human; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human