title: Novel cross talk between MEK and S6K2 in FGF-2 induced proliferation of SCLC cells.
abstract: Here, we show that fibroblast growth factor-2 (FGF-2) induces proliferation of H-510 and H-69 small cell lung cancer (SCLC) cells. However, the optimal response to FGF-2 was obtained at 10-fold lower concentrations in H-510 cells. This correlated with the selective activation of the mitogen-activated protein kinase kinase (MEK) pathway in H-510, but not H-69 cells. Moreover, inhibition of MEK with PD098059 blocked FGF-2-induced proliferation in H-510 cells only. Similarly, ribosomal protein S6 kinase 2 (S6K2), a recently identified homologue of S6K1 was activated by FGF-2 in H-510, but not H-69 cells. This activation was independent of phosphatidylinositol-3 kinase, but was sensitive to inhibition of the MEK pathway. These data suggest that S6K2 is a novel downstream target of MEK. The potency of FGF-2 in H-510 cells might reflect this additional MEK/S6K2 signalling. In contrast to S6K2, S6K1 was activated in both SCLC cell lines. Inhibition of the mammalian target of rapamycin with 10 ng/ml rapamycin blocked S6K1 activation and proliferation of both lines. However, even at 100 ng/ml, rapamycin only partially inhibited S6K2. Strikingly, this correlated with inhibition of MEK signalling. Our data indicate that S6K1, and possibly S6K2, are involved in FGF-2-induced SCLC cell growth, a notion supported by the overexpression and higher baseline activity of both isoforms in SCLC lines, as compared to normal human type-II pneumocytes.
authors.affiliation: Lung Cancer Biology Group, Division of Medicine, Hammersmith Campus of Imperial College School of Medicine, London W12 ONN, UK.
authors.forename: O E
authors.initials: OE
authors.lastname: Pardo
authors.forename: A
authors.initials: A
authors.lastname: Arcaro
authors.forename: G
authors.initials: G
authors.lastname: Salerno
authors.forename: T D
authors.initials: TD
authors.lastname: Tetley
authors.forename: T
authors.initials: T
authors.lastname: Valovka
authors.forename: I
authors.initials: I
authors.lastname: Gout
authors.forename: M J
authors.initials: MJ
authors.lastname: Seckl
mesh_terms: D000595:Amino Acid Sequence; D018288:Carcinoma, Small Cell / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004789:Enzyme Activation; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008934:Mitogens / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D016222:Fibroblast Growth Factor 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D008934:Mitogens; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; C546842:MTOR protein, human; C496348:FGFR1 protein, human