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.

Genetic heterogeneity of asthma phenotypes identified by a clustering approach

“…More interestingly, ALCAM was identified as a common gene in three inflammatory diseases: Crohn's disease, rheumatoid arthritis and type 1 diabetes [32]. Furthermore, ALCAM interacts with ADAM17 (a disintegrin and metalloproteinase 17), which is implicated in immune cell development and function and has been shown to play a role in the epidermal barrier [33,34]. Interestingly, a further SNP in the CD200 gene (CD200 molecule), located in the same genomic region as ALCAM and encoding a protein also belonging to the Ig superfamily, was exclusively associated with the active adult-onset asthma phenotype.…”

Detection of Activated Leukocyte Cell Adhesion Molecule in the Serum of Breast Cancer Patients and Implications for Prognosis

“…ALCAM serum levels may be a sign of receptor activation and active shedding of the protein into the serum, i.e. by the protease A disintegrin and A metalloproteinase 17 (ADAM17), also known as tumor necrosis factor-α-converting enzyme (TACE) [23]. A potential drawback of our study is that we were not yet able to perform serial measurements of sALCAM.…”

Activated Leukocyte Cell Adhesion Molecule Is a Marker for Thyroid Carcinoma Aggressiveness and Disease-Free Survival

“…Proteolysis of the extracellular domain of ALCAM by tumor necrosis factor-alpha converting enzyme (TACE) leads to its shedding (29); soluble ALCAM levels have been measured in sera of cancer patients with divergent findings (27,30,31). However, studies on AL-CAM in TC patient specimens are limited (32).…”

“…ALCAM was detected in proteomic analysis of cell lysates from TC cell lines (TPC-1 and SKOV-3) and in their conditioned media, as well as in four PTCs and two medullary TCs by immunostaining (32). These authors demonstrated that the extracellular surface domain of ALCAM is cleaved by metalloproteinases ADAM17/TACE, which subsequently translocates to the cytoplasm, where it facilitates aggressive transformation of tumor cells.…”

“…addressed the role of ALCAM in thyroid tumor biology (32). ALCAM was detected in proteomic analysis of cell lysates from TC cell lines (TPC-1 and SKOV-3) and in their conditioned media, as well as in four PTCs and two medullary TCs by immunostaining (32).…”