title: Activated leukocyte cell adhesion molecule expression and shedding in thyroid tumors.
abstract: Activated leukocyte cell adhesion molecule (ALCAM, CD166) is expressed in various tissues, cancers, and cancer-initiating cells. Alterations in expression of ALCAM have been reported in several human tumors, and cell adhesion functions have been proposed to explain its association with cancer. Here we documented high levels of ALCAM expression in human thyroid tumors and cell lines. Through proteomic characterization of ALCAM expression in the human papillary thyroid carcinoma cell line TPC-1, we identified the presence of a full-length membrane-associated isoform in cell lysate and of soluble ALCAM isoforms in conditioned medium. This finding is consistent with proteolytically shed ALCAM ectodomains. Nonspecific agents, such as phorbol myristate acetate (PMA) or ionomycin, provoked increased ectodomain shedding. Epidermal growth factor receptor stimulation also enhanced ALCAM secretion through an ADAM17/TACE-dependent pathway. ADAM17/TACE was expressed in the TPC-1 cell line, and ADAM17/TACE silencing by specific small interfering RNAs reduced ALCAM shedding. In addition, the CGS27023A inhibitor of ADAM17/TACE function reduced ALCAM release in a dose-dependent manner and inhibited cell migration in a wound-healing assay. We also provide evidence for the existence of novel O-glycosylated forms and of a novel 60-kDa soluble form of ALCAM, which is particularly abundant following cell stimulation by PMA. ALCAM expression in papillary and medullary thyroid cancer specimens and in the surrounding non-tumoral component was studied by western blot and immunohistochemistry, with results demonstrating that tumor cells overexpress ALCAM. These findings strongly suggest the possibility that ALCAM may have an important role in thyroid tumor biology.
authors.affiliation: Proteomics Laboratory, Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Miccichè
authors.forename: Luca
authors.initials: L
authors.lastname: Da Riva
authors.forename: Marina
authors.initials: M
authors.lastname: Fabbi
authors.forename: Silvana
authors.initials: S
authors.lastname: Pilotti
authors.forename: Piera
authors.initials: P
authors.lastname: Mondellini
authors.forename: Silvano
authors.initials: S
authors.lastname: Ferrini
authors.forename: Silvana
authors.initials: S
authors.lastname: Canevari
authors.forename: Marco A
authors.initials: MA
authors.lastname: Pierotti
authors.forename: Italia
authors.initials: I
authors.lastname: Bongarzone
mesh_terms: D020410:Activated-Leukocyte Cell Adhesion Molecule / Q000235:genetics* / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002277:Carcinoma; D002291:Carcinoma, Papillary; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D040901:Proteomics; D034741:RNA, Small Interfering / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology
chemical_list: D020410:Activated-Leukocyte Cell Adhesion Molecule; D014408:Biomarkers, Tumor; D007476:Ionophores; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate