title: Aberrant splicing and protease involvement in mesothelin release from epithelioid mesothelioma cells.
abstract: Elevated amounts of soluble mesothelin-related proteins (SMRP) have already been reported in sera and pleural effusions from mesothelioma patients, providing a useful diagnostic marker for malignant pleural mesothelioma (MPM). However, the origin of SMRP is not yet understood. Production of SMRP could be related to abnormal splicing events leading to synthesis of a secreted protein (release) or to an enzymatic cleavage from membrane-bound mesothelin (ectodomain shedding). To test these hypotheses, we used a panel of mesothelioma cells established in culture from pleural effusions of MPM patients. Our in vitro results confirmed specific mesothelin expression and SMRP production in supernatants from epithelioid MPM cell lines, thus providing a relevant cellular model to study soluble mesothelin production mechanisms. The expression of mesothelin-encoding RNA variants was screened by reverse transcription-polymerase chain reaction experiments. Protease involvement in mesothelin cleavage from the cellular surface was investigated by treatment of MPM cells with GM6001, a broad-spectrum MMP- and ADAM-family inhibitor. GM6001 treatment significantly impaired SMRP production by MPM cell lines, in favor of an enzymatic-mediated shedding process. In addition, a splice variant transcript of mesothelin (variant 3) was detected in these MPM cell lines, in accordance with the release of a secreted part of the protein. Our results indicate that both mechanisms could be implicated in soluble mesothelin production by epithelioid mesothelioma cells.
authors.affiliation: INSERM U601, Département de Recherche en Cancérologie, Institut de Biologie/CHU, 44093 Nantes, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Sapede
authors.forename: Anne
authors.initials: A
authors.lastname: Gauvrit
authors.forename: Isabelle
authors.initials: I
authors.lastname: Barbieux
authors.forename: Martine
authors.initials: M
authors.lastname: Padieu
authors.forename: Laurent
authors.initials: L
authors.lastname: Cellerin
authors.forename: Christine
authors.initials: C
authors.lastname: Sagan
authors.forename: Arnaud
authors.initials: A
authors.lastname: Scherpereel
authors.forename: Gérard
authors.initials: G
authors.lastname: Dabouis
authors.forename: Marc
authors.initials: M
authors.lastname: Grégoire
mesh_terms: D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism; D058851:GPI-Linked Proteins; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D000090204:Mesothelin; D008654:Mesothelioma / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D010997:Pleural Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing
chemical_list: D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; D010447:Peptide Hydrolases; D000090204:Mesothelin