title: ERK and PI3K negatively regulate STAT-transcriptional activities in human melanoma cells: implications towards sensitization to apoptosis.
abstract: Signal transducers and activators of transcription (STAT) proteins nuclear translocation and transcriptional activity are regulated by diverse protein kinases in response to extracellular stimuli by cytokines, growth factors and stress. Using two melanoma-derived cell lines that exhibit marked differences in basal activities of MAPKs and PI3K-AKT, we studied changes both in STAT activities and in their sensitization to apoptosis. Activating mutations of B-RAF (T1796A) and impaired expression of PTEN are detected in LU1205, but not in FEMX melanoma cells, and are reflected in high basal levels of expression and activities of MAPKs and PI3K-AKT. Treatment with either PD98059 (PD) or LY294002 (LY), the pharmacological inhibitors of MEK-ERK and PI3K, respectively, markedly increased GAS-Luc activity in LU1205, but not in FEMX cells. Tyrosine phosphorylation of STAT3/5 and of JAK2 also increased upon treatment of LU1205 cells with either PD or LY, suggesting that constitutive active MAPK and PI3K signals inhibit tyrosine phosphorylation of JAK/STATs. Treatment of FEMX and LU1205 with PD sensitized the cells to apoptosis, albeit by TNFalpha and TRAIL death cascades, respectively, indicating that additional yet distinct targets are affected by each signaling pathway. Indeed, the combination of LY and PD treatment synergistically increased the apoptosis of LU1205 and FEMX cells. Overall, whereas PI3K and MAPK downregulate JAK-STAT signaling, additional targets are affected by these kinases and sensitizes melanoma to apoptosis via distinct death cascades.
authors.affiliation: Institute of Carcinogenesis, NN Blochin Cancer Research Center, Moscow, Russia.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Krasilnikov
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Ivanov
authors.forename: Jinali
authors.initials: J
authors.lastname: Dong
authors.forename: Ze'ev
authors.initials: Z
authors.lastname: Ronai
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D002867:Chromones; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008562:Membrane Glycoproteins; D008894:Milk Proteins; D009025:Morpholines; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D014443:Tyrosine; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one