title: Dual c-Jun N-terminal kinase-cyclin D1 and extracellular signal-related kinase-c-Jun disjunction in human melanoma.
abstract: BACKGROUND
  Activity of both c-Jun and cyclin D1 is deemed critical for melanoma cell proliferation. This functionality is corroborated by frequently elevated expression and activity of these proteins in human melanomas. Correspondingly, alleviating c-Jun and cyclin D1 function is vital to the success of antimelanoma therapeutics.
  
  
  OBJECTIVE
  To understand the role of the c-Jun N-terminal kinase (JNK) signalling pathway in melanoma cell proliferation and survival.
  
  
  METHODS
  The effect of JNK inhibitors SP600125 and JNK-IN-8 on the proliferation and survival of genetically highly representative human melanoma cell lines was studied in assays of proliferation and apoptosis. Changes in c-Jun and cyclin D1 protein and mRNA levels in response to JNK and mitogen-activated protein kinase kinase (MEK) inhibition were investigated through immunoblotting and quantitative reverse-transcription polymerase chain reaction. The effects of JNK and MEK inhibitors on cell-cycle distribution were assessed by flow cytometry.
  
  
  RESULTS
  We demonstrate the requirement of JNK signalling in melanoma cell proliferation and survival. While JNK inhibition suppressed the expression and activity of c-Jun, it failed to suppress cyclin D1 levels. Consistently with its inability to downregulate cyclin D1, JNK inhibition failed to induce G1 arrest. In contrast, the blockade of MEK-extracellular signal-regulated kinase (ERK) signalling, although unable to suppress c-Jun activity and expression, paradoxically abated cyclin D1 levels and triggered G1 arrest. This previously unreported dual disconnect between JNK-cyclin D1 and ERK-c-Jun levels was confirmed by concomitant JNK and BRAF inhibition, which suppressed both c-Jun and cyclin D1 levels and exhibited a heightened antiproliferative response.
  
  
  CONCLUSIONS
  Dual disjunction between JNK-cyclin D1 and ERK-c-Jun signalling forms the basis for further investigation of combined JNK and MAPK signalling blockade as a more effective therapeutic approach in human melanoma.
authors.affiliation: Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Pathria
authors.affiliation: Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: B
authors.initials: B
authors.lastname: Garg
authors.affiliation: Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Garg
authors.affiliation: Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Wagner
authors.affiliation: Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: S N
authors.initials: SN
authors.lastname: Wagner
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008545:Melanoma / Q000401:mortality* / Q000473:pathology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D012878:Skin Neoplasms / Q000401:mortality* / Q000473:pathology; D014407:Tumor Cells, Cultured
chemical_list: D000873:Anthracenes; C530104:CCND1 protein, human; D047428:Protein Kinase Inhibitors; D019938:Cyclin D1; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases