title: MAPK inhibitors differently modulate TGF-β/Smad signaling in HepG2 cells.
abstract: The aim of this study was to investigate the mitogen-activated protein kinase (MAPK) pathway, which crosstalk with TGF-β/Smad signaling via linker phosphorylation of Smad2/3 to promote hepatocarcinogenesis. After DEN-induced hepatocellular carcinoma (HCC) in rats showed increased phosphorylation of JNK1/2, p38, and ERK1/2, we next antagonized TGF-β1-induced phosphorylation of JNK1/2, p38, ERK1/2, Smad2/3 signaling in HepG2 cells using SP600125, SB203580, and PD98059, respectively. Cell proliferation and invasion were assessed by MTT assay and transwell invasion chambers, respectively. Smad2/3, Smad4, and Smad7 expressions and PAI-1 messenger RNA (mRNA) transcription were measured by using immuno-precipitation/immuno-blotting and real-time RT-PCR, respectively. All the MAPK-specific inhibitors suppressed cell invasion, while all but PD98059 suppressed cell proliferation. Both SP600125 and SB203580 blocked pSmad2C/L and oncogenic pSmad3L. PD98059 blocked pSmad2L but had no effect on elevated pSmad2C and oncogenic pSmad3L. All but PD98059 blocked Smad2/3/4 complex formation and restored Smad7 expression, while all the three MAPK-Specific inhibitors repressed PAI-1 mRNA transcription. Both SP600125 and SB203580 inhibited HepG2 cells' proliferation and invasion by blocking oncogenic pSmad3L and Smad2/3/4 complex formation. PD98059 repressed PAI-1 mRNA by an unknown mechanism.
authors.affiliation: Department of Pharmacology and Institute of Natural Medicine, Anhui Medical University, Hefei, 230032, China.
authors.forename: A
authors.initials: A
authors.lastname: Boye
authors.forename: H
authors.initials: H
authors.lastname: Kan
authors.forename: C
authors.initials: C
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Jiang
authors.forename: X
authors.initials: X
authors.lastname: Yang
authors.forename: S
authors.initials: S
authors.lastname: He
authors.forename: Y
authors.initials: Y
authors.lastname: Yang
mesh_terms: D000818:Animals; D063646:Carcinogenesis / Q000235:genetics*; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D004052:Diethylnitrosamine / Q000633:toxicity; D005419:Flavonoids / Q000008:administration & dosage; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009361:Neoplasm Invasiveness / Q000235:genetics; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis; D051381:Rats; D051785:Smad Proteins / Q000096:biosynthesis* / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D005419:Flavonoids; D017395:Plasminogen Activator Inhibitor 1; C051321:SERPINE1 protein, human; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; D004052:Diethylnitrosamine; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one