title: Semaphorin SEMA3F affects multiple signaling pathways in lung cancer cells.
abstract: Loss of SEMA3F occurs frequently in lung cancer and correlates with advanced stage of disease. We previously reported that SEMA3F blocked tumor formation by H157 lung cancer cells in a rat orthotopic model. This was associated with loss of activated alpha(V)beta(3) integrin, impaired cell adhesion to extracellular matrix components, and down-regulation of phospho-extracellular signal-regulated kinase 1/2 (ERK1/2). These results suggested that SEMA3F might interfere with integrin outside-in signaling. In the present report, we found that SEMA3F decreased adhesion to vitronectin, whereas integrin-linked kinase (ILK) kinase activity was down-regulated in SEMA3F-expressing H157 cells. Exposure to SEMA3F-conditioned medium led to diminution of phospho-ERK1/2 in four of eight lung cancer cell lines, and ILK silencing by small interfering RNA led to similar loss of phospho-ERK1/2 in H157 cells. Moreover, SEMA3F expression (with constitutive and inducible systems) also reduced AKT and signal transducer and activator of transcription 3 (STAT3) phosphorylation independently of ILK-ERK1/2. These signaling changes extended downstream to hypoxia-inducible factor-1alpha (HIF-1alpha) protein and vascular endothelial growth factor (VEGF) mRNA levels, which were both reduced in three of four SEMA3F-transfected cell lines. Mechanistically, the effects on HIF-1alpha were consistent with inhibition of its AKT-driven protein translation initiation, with no effect on HIF-1alpha mRNA level or protein degradation. Furthermore, when H157 cells were injected s.c. in nude mice, tumors derived from SEMA3F-expressing cells showed lower microvessel density and tumor growth. These results show that SEMA3F negatively affects ILK-ERK1/2 and AKT-STAT3 signaling, along with inhibition of HIF-1alpha and VEGF. These changes would be anticipated to contribute significantly to the observed antitumor activity of SEMA3F.
authors: Division of Medical Oncology, University of Colorado Health Sciences Center, Aurora, Colorado, USA.
authors: Vincent A
authors: VA
authors: Potiron
authors: Girish
authors: G
authors: Sharma
authors: Patrick
authors: P
authors: Nasarre
authors: Jonathan A
authors: JA
authors: Clarhaut
authors: Hellmut G
authors: HG
authors: Augustin
authors: Robert M
authors: RM
authors: Gemmill
authors: Joëlle
authors: J
authors: Roche
authors: Harry A
authors: HA
authors: Drabkin
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008175:Lung Neoplasms / Q000098:blood supply / Q000235:genetics / Q000378:metabolism* / Q000628:therapy*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors; D009389:Neovascularization, Pathologic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D042442:Vascular Endothelial Growth Factors / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D000099200:Scaffold Protein ILK
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008565:Membrane Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D042442:Vascular Endothelial Growth Factors; D000099200:Scaffold Protein ILK; C497442:HIF1A protein, human; C491230:SEMA3F protein, human; C494086:STAT3 protein, human