title: A large-scale RNAi screen identifies LCMR1 as a critical regulator of Tspan8-mediated melanoma invasion.
abstract: Melanoma is the deadliest form of skin cancer owing to its proclivity to metastasise, and recently developed therapies have not yielded the expected results, because almost all patients relapse. Therefore, understanding the molecular mechanisms that underlie early invasion by melanoma cells is crucial to improving patient survival. We have previously shown that, whereas the Tetraspanin 8 protein (Tspan8) is undetectable in normal skin and benign lesions, its expression arises with the progression of melanoma and is sufficient to increase cell invasiveness. Therefore, to identify Tspan8 transcriptional regulators that could explain the onset of Tspan8 expression, thereby conferring an invasive phenotype, we performed an innovative RNA interference-based screen, which, for the first time, identified several Tspan8 repressors and activators, such as GSK3β, PTEN, IQGAP1, TPT1 and LCMR1. LCMR1 is a recently identified protein that is overexpressed in numerous carcinomas; its expression and role, however, had not previously been studied in melanoma. The present study identified Tspan8 as the first LCMR1 target that could explain its function in carcinogenesis. LCMR1 modulation was sufficient to positively regulate endogenous Tspan8 expression, with concomitant in vitro phenotypic changes such as loss of melanoma cell-matrix adherence and increase in invasion, and Tspan8 expression promoted tumourigenicity in vivo. Moreover, LCMR1 and Tspan8 overexpression were shown to correlate in melanoma lesions, and both proteins could be downregulated in vitro by vemurafenib. In conclusion, this study highlights the importance of Tspan8 and its regulators in the control of early melanoma invasion and suggests that they may be promising new therapeutic targets downstream of the RAF-MEK-ERK signalling pathway.
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: G
authors.initials: G
authors.lastname: Agaësse
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: L
authors.initials: L
authors.lastname: Barbollat-Boutrand
authors.affiliation: Université Grenoble-Alpes, Grenoble, France.|CEA, BIG-BGE, Biomics, Grenoble, France.|Inserm, BGE, Grenoble, France.
authors.forename: E
authors.initials: E
authors.lastname: Sulpice
authors.affiliation: Université Grenoble-Alpes, Grenoble, France.|CEA, BIG-BGE, Biomics, Grenoble, France.|Inserm, BGE, Grenoble, France.
authors.forename: R
authors.initials: R
authors.lastname: Bhajun
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: M
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 Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: O
authors.initials: O
authors.lastname: Berthier-Vergnes
authors.affiliation: Clermont Université, Université d'Auvergne, Imagerie Moléculaire et Thérapie Vectorisée, BP, Clermont-Ferrand, France.|Inserm, U 990, Clermont-Ferrand, France.
authors.forename: F
authors.initials: F
authors.lastname: Degoul
authors.affiliation: Département de Biopathologie, Centre Léon Bérard, Lyon, France.
authors.forename: A
authors.initials: A
authors.lastname: de la Fouchardière
authors.affiliation: Laboratoire CarMeN (INSERM 1060, INRA 1397, INSA), Université de Lyon, Lyon, France.
authors.forename: E
authors.initials: E
authors.lastname: Berger
authors.affiliation: Centre de Recherche en Cancérologie de Lyon, CNRS UMR5286, Inserm U1052, Université de Lyon, Université Lyon 1, Lyon, France.
authors.forename: T
authors.initials: T
authors.lastname: Voeltzel
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: J
authors.initials: J
authors.lastname: Lamartine
authors.affiliation: Université Grenoble-Alpes, Grenoble, France.|CEA, BIG-BGE, Biomics, Grenoble, France.|Inserm, BGE, Grenoble, France.
authors.forename: X
authors.initials: X
authors.lastname: Gidrol
authors.affiliation: Université de Lyon, Lyon, France.|Université Lyon 1, Lyon, France.|CNRS, UMR5534, Centre de Génétique et de Physiologie Moléculaires et Cellulaires, Villeurbanne, France.
authors.forename: I
authors.initials: I
authors.lastname: Masse
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D064593:Heterografts; D006801:Humans; D008297:Male; D056892:Mediator Complex / Q000235:genetics* / Q000378:metabolism; D008545:Melanoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D034622:RNA Interference; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D059470:Tetraspanins / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D000090324:Tumor Protein, Translationally-Controlled 1
chemical_list: C558319:MED19 protein, human; D056892:Mediator Complex; C000715647:TPT1 protein, human; C065609:TSPAN8 protein, human; D059470:Tetraspanins; C000715648:Tpt1 protein, mouse; D000090324:Tumor Protein, Translationally-Controlled 1