The role of cAMP-MAPK signalling in the regulation of human hepatocellular carcinoma growth in vitro

C. Schmidt, Iain H. McKillop, Paul A. Cahill, James V. Sitzmann

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Objective. We have previously identified that primary human hepatocellular carcinoma (HCC) is associated with altered guanine nucleotide regulatory protein (G-protein) expression concomitant with decreased adenylyl cyclase (AC) and increased mitogen activated protein kinase (MAPK) activity in vivo. This study aims to address the potential link between Gs protein regulation of AC activity/cyclic adenosine monophosphate (cAMP) production and the subsequent downstream regulation of MAPK activity and mitogenesis. Design. Pharmacological agents which selectively interact with specific target proteins involved in signal transduction via the Gs-AC-cAMP-MAPK signalling pathway were employed in cultured human HCC cell lines in these studies. These agents allow us to address the role of individual components of these pathways in the regulation of mitogenesis in HCC. Methods. These studies utilized three distinct human HCC cell lines (HepG2, Hep3B and SKHep) in the absence and presence of agents that alter AC-cAMP dependent signalling. De novo DNA synthesis was determined as a marker of altered cellular proliferation, and MAPK activity was determined as the ability to catalyse myelin basic protein (MBP) phosphorylation. Results. 8-Bromo-cAMP (8-Br-cAMP; a cell-permeable cAMP analogue) and forskolin (AC activator) dose-dependently decreased thymidine incorporation in all three cell lines. In addition, serum-stimulated [3H] thymidine incorporation was significantly decreased in HepG2, Hep3B and SKHep cell lines following treatment with either 8-Br-cAMP or forskolin. By contrast, MDL12330A (MDL; irreversible AC inhibitor) enhanced thymidine incorporation in all three cell lines. Treatment with either 8-Br-cAMP or forskolin significantly decreased serum-stimulated MAPK activity. Conclusions. These data suggest that cAMP acts as an anti-mitogenic agent in these hepatic tumorigenic cell lines in vitro such that inhibition of AC activity promotes MAPK activity and cellular mitogenesis in HCC.

Original languageEnglish (US)
Pages (from-to)1393-1399
Number of pages7
JournalEuropean Journal of Gastroenterology and Hepatology
Volume11
Issue number12
StatePublished - 1999
Externally publishedYes

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Mitogen-Activated Protein Kinases
Cyclic AMP
Hepatocellular Carcinoma
Adenylyl Cyclases
Growth
Cell Line
Colforsin
Thymidine
8-Bromo Cyclic Adenosine Monophosphate
Myelin Basic Protein
In Vitro Techniques
Serum
GTP-Binding Proteins
Hepatocytes
Signal Transduction
Proteins
Phosphorylation
Cell Proliferation
Pharmacology
DNA

Keywords

  • cAMP
  • G-proteins
  • Hepatocellular carcinoma
  • MAPK
  • Mitogenesis

ASJC Scopus subject areas

  • Gastroenterology

Cite this

The role of cAMP-MAPK signalling in the regulation of human hepatocellular carcinoma growth in vitro. / Schmidt, C.; McKillop, Iain H.; Cahill, Paul A.; Sitzmann, James V.

In: European Journal of Gastroenterology and Hepatology, Vol. 11, No. 12, 1999, p. 1393-1399.

Research output: Contribution to journalArticle

Schmidt, C. ; McKillop, Iain H. ; Cahill, Paul A. ; Sitzmann, James V. / The role of cAMP-MAPK signalling in the regulation of human hepatocellular carcinoma growth in vitro. In: European Journal of Gastroenterology and Hepatology. 1999 ; Vol. 11, No. 12. pp. 1393-1399.
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AB - Objective. We have previously identified that primary human hepatocellular carcinoma (HCC) is associated with altered guanine nucleotide regulatory protein (G-protein) expression concomitant with decreased adenylyl cyclase (AC) and increased mitogen activated protein kinase (MAPK) activity in vivo. This study aims to address the potential link between Gs protein regulation of AC activity/cyclic adenosine monophosphate (cAMP) production and the subsequent downstream regulation of MAPK activity and mitogenesis. Design. Pharmacological agents which selectively interact with specific target proteins involved in signal transduction via the Gs-AC-cAMP-MAPK signalling pathway were employed in cultured human HCC cell lines in these studies. These agents allow us to address the role of individual components of these pathways in the regulation of mitogenesis in HCC. Methods. These studies utilized three distinct human HCC cell lines (HepG2, Hep3B and SKHep) in the absence and presence of agents that alter AC-cAMP dependent signalling. De novo DNA synthesis was determined as a marker of altered cellular proliferation, and MAPK activity was determined as the ability to catalyse myelin basic protein (MBP) phosphorylation. Results. 8-Bromo-cAMP (8-Br-cAMP; a cell-permeable cAMP analogue) and forskolin (AC activator) dose-dependently decreased thymidine incorporation in all three cell lines. In addition, serum-stimulated [3H] thymidine incorporation was significantly decreased in HepG2, Hep3B and SKHep cell lines following treatment with either 8-Br-cAMP or forskolin. By contrast, MDL12330A (MDL; irreversible AC inhibitor) enhanced thymidine incorporation in all three cell lines. Treatment with either 8-Br-cAMP or forskolin significantly decreased serum-stimulated MAPK activity. Conclusions. These data suggest that cAMP acts as an anti-mitogenic agent in these hepatic tumorigenic cell lines in vitro such that inhibition of AC activity promotes MAPK activity and cellular mitogenesis in HCC.

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