title: Downstream effectors of oncogenic ras in multiple myeloma cells.
abstract: Ectopic expression of mutated K-ras or N-ras in the interleukin 6 (IL-6)-dependent ANBL6 multiple myeloma cell line induces cytokine-independent growth. To investigate the signaling pathways activated by oncogenic ras that may stimulate IL-6-independent growth, we compared ANBL6 cells stably transfected with mutated K or N-ras genes with wild-type ras-expressing control cells identically transfected with an empty vector. Upon depletion of IL-6, both mutated ras-containing myeloma lines demonstrated constitutive activation of mitogen-activated extracellular kinase 2(MEK)/extracellular signal-regulated kinase (ERK), phosphatidylinositol-3 kinase (PI3-kinase)/AKT, mammalian target of rapamycin (mTOR)/p70S6-kinase, and nuclear factor kappa B (NF-kappa B) pathways. In contrast, signal transducer and activator of transcription-3 (STAT-3) was not constitutively tyrosine phosphorylated in mutant ras-expressing cells. We used several maneuvers in attempts to selectively target these constitutively active pathways. The mTOR inhibitors rapamycin and CCI-779, the PI3-kinase inhibitor LY294002, and the MEK inhibitor PD98059 all significantly curtailed growth of mutant ras-containing cells. Farnesyl transferase inhibitors, used to target ras itself, had modest effects only against mutant N-ras-containing cells. Growth of mutant N-ras-containing myeloma cells was also inhibited by acute expression of the IKB superrepressor gene, which abrogated NF-kappa B activation. These results indicate that several pathways contributing to stimulation of cytokine-independent growth are activated downstream of oncogenic ras in myeloma cells. They also suggest that therapeutic strategies that target these pathways may be particularly efficacious in patients whose myeloma clones contain ras mutations.
authors.affiliation: Hematology-Oncology Division, West Los Angeles Veteran's Administration-University of California Los Angeles Medical Center, Los Angeles, CA 90073, USA.
authors.forename: Liping
authors.initials: L
authors.lastname: Hu
authors.forename: Yijiang
authors.initials: Y
authors.lastname: Shi
authors.forename: Jung-hsin
authors.initials: JH
authors.lastname: Hsu
authors.forename: Joseph
authors.initials: J
authors.lastname: Gera
authors.forename: Brian
authors.initials: B
authors.lastname: Van Ness
authors.forename: Alan
authors.initials: A
authors.lastname: Lichtenstein
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors; D002453:Cell Cycle; D002867:Chromones / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051231:Farnesyltranstransferase; D005419:Flavonoids / Q000494:pharmacology; D011905:Genes, ras; D020672:I-kappa B Proteins / Q000235:genetics / Q000502:physiology; D015850:Interleukin-6 / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009025:Morpholines / Q000494:pharmacology; D009101:Multiple Myeloma / Q000235:genetics* / Q000473:pathology; D016328:NF-kappa B / Q000502:physiology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D015689:Oncogene Protein p21(ras) / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000502:physiology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins / Q000502:physiology; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000502:physiology; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
chemical_list: D019883:Alkyl and Aryl Transferases; D002867:Chromones; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D051231:Farnesyltranstransferase; D005419:Flavonoids; D020672:I-kappa B Proteins; D015850:Interleukin-6; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D016328:NF-kappa B; D009363:Neoplasm Proteins; D015689:Oncogene Protein p21(ras); D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D050796:STAT3 Transcription Factor; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D015534:Trans-Activators; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one