title: Hepatocyte growth factor/scatter factor activates proliferation in melanoma cells through p38 MAPK, ATF-2 and cyclin D1.
abstract: Members of the mitogen-activated protein kinase (MAPK) superfamily, including p38 kinase and SAPK/JNK, play a central role in mediating cellular response to environmental stress, growth factors and cytokines. Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional cytokine capable of eliciting mitogenic, motogenic and morphogenetic activities in responsive cells, and has been implicated in tumor development and metastasis. Binding of HGF/SF to its tyrosine kinase receptor c-Met stimulates multiple signal transduction pathways, leading to the activation of numerous transcription factors. We here report that HGF/SF can induce cyclin D1 expression in mouse melanoma cells, and that this up-regulation is mediated in part by the activating transcription factor-2 (ATF-2). HGF/SF-mediated phosphorylation of ATF-2 was reduced in the presence of either the p38 kinase-specific inhibitor SB203580, a dominant negative p38 mutant, the SAPK/JNK inhibitor JNK-interacting protein-1 (JIP-1), or the phosphatidylinositol 3-kinase (PI3K)-specific inhibitor LY294002. Activation of p38 kinase by HGF/SF was partially blocked by the PI3K-specific inhibitor as well. The upstream kinases for p38, MKK3/6, did not become activated following HGF/SF exposure, and ATF-2 activation was undiminished by transient transfection of a dominant negative MKK6 mutant. However, transcriptional up-regulation of cyclin D1 by HGF/SF was partially inhibited by the p38 kinase-specific inhibitor, and cyclin D1 protein induction was partially blocked by a dominant negative ATF-2 mutant. Notably, the p38 kinase-specific inhibitor was able to block melanoma cell proliferation but not motility. We conclude that the ATF-2 transcription factor becomes activated by HGF/SF through p38 MAPK and SAPK/JNK. Moreover, the p38-ATF-2 pathway can help mediate proliferation signals in tumor cells through transcriptional activation of key cell cycle regulators.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4264, USA.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Recio
authors.forename: Glenn
authors.initials: G
authors.lastname: Merlino
mesh_terms: D051698:Activating Transcription Factor 2; D000818:Animals; D002455:Cell Division; D002465:Cell Movement; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology*; D019938:Cyclin D1 / Q000235:genetics / Q000502:physiology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D007700:Kinetics; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; D014157:Transcription Factors; D019938:Cyclin D1; D017228:Hepatocyte Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases