title: Tetraspanin 8 is a novel regulator of ILK-driven β1 integrin adhesion and signaling in invasive melanoma cells.
abstract: Melanoma is well known for its propensity for lethal metastasis and resistance to most current therapies. Tumor progression and drug resistance depend to a large extent on the interplay between tumor cells and the surrounding matrix. We previously identified Tetraspanin 8 (Tspan8) as a critical mediator of melanoma invasion, whose expression is absent in healthy skin. The present study investigated whether Tspan8 may influence cell-matrix anchorage and regulate downstream molecular pathways leading to an aggressive behavior. Using silencing and ectopic expression strategies, we showed that Tspan8-mediated invasion of melanoma cells resulted from defects in cell-matrix anchorage by interacting with β1 integrins and by interfering with their clustering, without affecting their surface or global expression levels. These effects were associated with impaired phosphorylation of integrin-linked kinase (ILK) and its downstream target Akt-S473, but not FAK. Specific blockade of Akt or ILK activity strongly affected cell-matrix adhesion. Moreover, expression of a dominant-negative form of ILK reduced β1 integrin clustering and cell-matrix adhesion. Finally, we observed a tumor-promoting effect of Tspan8 in vivo and a mutually exclusive expression pattern between Tspan8 and phosphorylated ILK in melanoma xenografts and human melanocytic lesions. Altogether, the in vitro, in vivo and in situ data highlight a novel regulatory role for Tspan8 in melanoma progression by modulating cell-matrix interactions through β1 integrin-ILK axis and establish Tspan8 as a negative regulator of ILK activity. These findings emphasize the importance of targeting Tspan8 as a means of switching from low- to firm-adhesive states, mandatory to prevent tumor dissemination.
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France.|Current address: Department of Dermatology, University of Colorado, Aurora, Colorado, USA.
authors.forename: Manale
authors.initials: M
authors.lastname: El Kharbili
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France.
authors.forename: Clément
authors.initials: C
authors.lastname: Robert
authors.affiliation: Clermont Université, Université d'Auvergne, Imagerie Moléculaire et Thérapie Vectorisée, Clermont-Ferrand, France.|Inserm, U990, Clermont-Ferrand, France.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Witkowski
authors.affiliation: Laboratoire CarMeN (INSERM 1060, INRA1397, INSA), Université Lyon 1, Lyon, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Danty-Berger
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France.
authors.forename: Laetitia
authors.initials: L
authors.lastname: Barbollat-Boutrand
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Masse
authors.affiliation: Université Lyon 1, Fédération de Recherche Santé Lyon-Est, ANIPATH, Faculté Laennec, Lyon, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gadot
authors.affiliation: Département de Biopathologie, Centre Léon Bérard, Lyon, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: de la Fouchardière
authors.affiliation: Department of Integrative Oncology, British Columbia Cancer Research Center, Vancouver, Canada.
authors.forename: Paul C
authors.initials: PC
authors.lastname: McDonald
authors.affiliation: Department of Integrative Oncology, British Columbia Cancer Research Center, Vancouver, Canada.
authors.forename: Shoukat
authors.initials: S
authors.lastname: Dedhar
authors.affiliation: INSERM U602, Villejuif, France.|Current address: INSERM U1193, Hôpital Paul Brousse, Villejuif, France.
authors.forename: François
authors.initials: F
authors.lastname: Le Naour
authors.affiliation: Clermont Université, Université d'Auvergne, Imagerie Moléculaire et Thérapie Vectorisée, Clermont-Ferrand, France.|Inserm, U990, Clermont-Ferrand, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Degoul
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Villeurbanne, France.
authors.forename: Odile
authors.initials: O
authors.lastname: Berthier-Vergnes
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008819:Mice, Nude; D018613:Microscopy, Confocal; D009154:Mutation; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000235:genetics*; D059470:Tetraspanins / Q000235:genetics* / Q000378:metabolism; D014183:Transplantation, Heterologous; D000099200:Scaffold Protein ILK
chemical_list: D019012:Integrin beta1; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D059470:Tetraspanins; D000099200:Scaffold Protein ILK; C065609:TSPAN8 protein, human
keywords: ILK; integrin; matrix; melanoma; tetraspanin 8