PMID- 19661225 OWN - NLM STAT- MEDLINE DCOM- 20100203 LR - 20211203 IS - 1552-5783 (Electronic) IS - 0146-0404 (Linking) VI - 51 IP - 1 DP - 2010 Jan TI - The PI3K/Akt and mTOR/P70S6K signaling pathways in human uveal melanoma cells: interaction with B-Raf/ERK. PG - 421-9 LID - 10.1167/iovs.09-3974 [doi] AB - PURPOSE: Activated B-Raf alone cannot induce melanoma but must cooperate with other signaling pathways. The phosphatidylinositol 3-kinase (PI3K)/Akt and mammalian target of rapamycin (mTOR)/p70S6K pathways are critical for tumorigenesis. The authors investigated the role of these pathways in uveal melanoma cells. METHODS: The effects of PI3K and mTOR activation and inhibition on the proliferation of human uveal melanoma cell lines expressing either activated (WT)B-Raf or (V600E)B-Raf were investigated. Interactions among PI3K, mTOR, and B-Raf/ERK were studied. RESULTS: Inhibition of PI3K deactivated P70S6 kinase, reduced cell proliferation by 71% to 84%, and increased apoptosis by a factor of 5.0 to 8.4 without reducing ERK1/2 activation, indicating that ERK plays no role in mediating PI3K in these processes. In contrast, rapamycin-induced inhibition of mTOR did not significantly affect cell proliferation because it simultaneously stimulated PI3K/Akt activation and cyclin D1 expression. Regardless of B-Raf mutation status, cotreatment with the PI3K inhibitor effectively sensitized all melanoma cell lines to the B-Raf or ERK1/2 inhibition-induced reduction of cell proliferation. B-Raf/ERK and PI3K signaling, but not mTOR signaling, converged to control cyclin D1 expression. Moreover, p70S6K required the activation of ERK1/2. These data demonstrate that PI3K/Akt and mTOR/P70S6K interact with B-Raf/ERK. CONCLUSIONS: Activated PI3K/Akt attenuates the inhibitory effects of rapamycin on cell proliferation and thus serves as a negative feedback mechanism. This finding suggests that rapamycin is unlikely to inhibit uveal melanoma growth. In contrast, targeting PI3K while inhibiting B-Raf/ERK may be a promising approach to reduce the proliferation of uveal melanoma cells. FAU - Babchia, Narjes AU - Babchia N AD - Centre de Recherche des Cordeliers, Universite Pierre et Marie Curie, Paris, France. FAU - Calipel, Armelle AU - Calipel A FAU - Mouriaux, Frederic AU - Mouriaux F FAU - Faussat, Anne-Marie AU - Faussat AM FAU - Mascarelli, Frederic AU - Mascarelli F LA - eng PT - Journal Article DEP - 20090806 PL - United States TA - Invest Ophthalmol Vis Sci JT - Investigative ophthalmology & visual science JID - 7703701 RN - 0 (Enzyme Inhibitors) RN - 0 (Intracellular Signaling Peptides and Proteins) RN - 0 (Phosphoinositide-3 Kinase Inhibitors) RN - EC 2.7.1.1 (MTOR protein, human) RN - EC 2.7.11.1 (Protein Serine-Threonine Kinases) RN - EC 2.7.11.1 (Proto-Oncogene Proteins B-raf) RN - EC 2.7.11.1 (Proto-Oncogene Proteins c-akt) RN - EC 2.7.11.1 (Ribosomal Protein S6 Kinases, 70-kDa) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 2.7.11.24 (Extracellular Signal-Regulated MAP Kinases) RN - W36ZG6FT64 (Sirolimus) SB - IM MH - Apoptosis MH - Blotting, Western MH - Cell Cycle/physiology MH - Cell Proliferation MH - Dose-Response Relationship, Drug MH - Enzyme Activation/drug effects MH - Enzyme Inhibitors/pharmacology MH - Extracellular Signal-Regulated MAP Kinases/*metabolism MH - Feedback, Physiological MH - Humans MH - Intracellular Signaling Peptides and Proteins/*physiology MH - Melanoma/*metabolism/pathology MH - Phosphatidylinositol 3-Kinases/*physiology MH - Phosphoinositide-3 Kinase Inhibitors MH - Phosphorylation MH - Protein Serine-Threonine Kinases/*physiology MH - Proto-Oncogene Proteins B-raf/*metabolism MH - Proto-Oncogene Proteins c-akt/*metabolism MH - Ribosomal Protein S6 Kinases, 70-kDa/*metabolism MH - Signal Transduction/*physiology MH - Sirolimus/pharmacology MH - TOR Serine-Threonine Kinases MH - Tumor Cells, Cultured MH - Uveal Neoplasms/*metabolism/pathology EDAT- 2009/08/08 09:00 MHDA- 2010/02/04 06:00 CRDT- 2009/08/08 09:00 PHST- 2009/08/08 09:00 [entrez] PHST- 2009/08/08 09:00 [pubmed] PHST- 2010/02/04 06:00 [medline] AID - iovs.09-3974 [pii] AID - 10.1167/iovs.09-3974 [doi] PST - ppublish SO - Invest Ophthalmol Vis Sci. 2010 Jan;51(1):421-9. doi: 10.1167/iovs.09-3974. Epub 2009 Aug 6.