Up-regulation of METCAM/MUC18 promotes motility, invasion, and tumorigenesis of human breast cancer cells

Abstract

BackgroundConflicting research has identified METCAM/MUC18, an integral membrane cell adhesion molecule (CAM) in the Ig-like gene super-family, as both a tumor promoter and a tumor suppressor in the development of breast cancer. To resolve this, we have re-investigated the role of this CAM in the progression of human breast cancer cells.MethodsThree breast cancer cell lines were used for the tests: one luminal-like breast cancer cell line, MCF7, which did not express any METCAM/MUC18, and two basal-like breast cancer cell lines, MDA-MB-231 and MDA-MB-468, which expressed moderate levels of the protein.MCF7 cells were transfected with the human METCAM/MUC18 cDNA to obtain G418-resistant clones which expressed the protein and were used for testing effects of human METCAM/MUC18 expression on in vitro motility and invasiveness, and in vitro and in vivo tumorigenesis. Both MDA-MB-231 and MDA-MB-468 cells already expressed METCAM/MUC18. They were directly used for in vitro tests in the presence and absence of an anti-METCAM/MUC18 antibody.ResultsIn MCF7 cells, enforced METCAM/MUC18 expression increased in vitro motility, invasiveness, anchorage-independent colony formation (in vitro tumorigenesis), and in vivo tumorigenesis. In both MDA-MB-231 and MDA-MB-468 cells, the anti-METCAM/MUC18 antibody inhibited both motility and invasiveness. Though both MDA-MB-231 and MDA-MB-468 cells established a disorganized growth in 3D basement membrane culture assay, the introduction of the anti-METCAM/MUC18 antibody completely destroyed their growth in the 3D culture.ConclusionThese findings support the notion that human METCAM/MUC18 expression promotes the progression of human breast cancer cells by increasing their motility, invasiveness and tumorigenesis.

Significance of Expression of Human METCAM/MUC18 in Nasopharyngeal Carcinomas and Metastatic Lesions

“…The extract from each frozen normal NP or NPC tissue was prepared as described (Wu et al, 2001a;Wu et al, 2001b;Wu, 2004;Wu et al, 2005;Chiang et al, 2005;Wu et al, 2008;Wu et al, 2011;Zeng et al, 2011;Zeng et al, 2012a). A portion of the homogenate was used for RNA preparation as described above.…”

“…The rest of the homogenate was used for making a Western blot lysate (Wu et al, 2001a;Wu et al, 2001b;Wu, 2004;Wu et al, 2005;Chiang et al, 2005;Wu et al, 2008;Wu et al, 2011;Zeng et al, 2011;Zeng et al, 2012a). HuMETCAM/MUC18 protein expression in cellular and tissue extracts was determined by the standard procedure of Western blot analysis by using a 1/235-350 dilution of the chicken anti-recombinant huMETCAM/ MUC18 protein IgY (reacting at room temperature for 2-5 hours or at the cold room for 16 hours) (Wu et al, 2001a;Wu et al, 2001b;Wu, 2004;Wu et al, 2005;Wu et al, 2008;Wu et al, 2011;Zeng et al, 2011;Zeng et al, 2012a). The image of the huMETCAM/ MUC18 band was scanned with an Epson Photo Scanner model 1260 and its intensity was quantitatively determined by a NIH Image J program version 1.31.…”

“…Based on the following reasons, we hypothesize that the expression of human METCAM/MUC18 (huMETCAM/ MUC18) is likely to play a role in the malignant progression of NPC: (a) the huMETCAM/MUC18 gene resides in the region of the chromosome11q22-23, in which hyper-methylation is associated with the NPC development during the progression of NPC (Lung et al, 2004;Lung et al, 2005), and (b) HuMETCAM/MUC18, a cell adhesion molecule (CAM) in the immunoglobulin gene super family, which is expressed in several normal tissues, such as hair follicular cells, smooth muscle cells, endothelial cells, cerebellum, normal mammary epithelial cells, basal cells of the lung, activated T cells, and intermediate trophoblast (Shih, 1999), has been evident in playing very intriguing roles in the progression of several epithelial cancers (Shih, 1999;Wu, 2005). Over-expression of huMETCAM/MUC18 promotes the metastasis of melanoma (Xie et al, 1997;Schlag-bauerWadl et al, 1999;Shih, 1999;Wu, 2005;Wu et al, 2008), prostate cancer (Wu et al, 2001a;Wu et al, 2001b;Wu, 2004;Wu et al, 2004;Wu et al, 2005;Wu et al, 2011), angiosarcomas (Wu, 2005), osteosarcoma (McGary et al, 2003), and breast cancer (Zeng et al, 2011;Zeng et al, 2012a;Zeng et al, 2012b). On the contrary, under-expression correlates with the malignant progression of haemangioma (Li et al, 2003) and over-expression of huMETCAM/MUC18 suppresses the tumorigenesis of one mouse melanoma cell line and human ovarian cancer cell lines in an immunodeficient mouse model (Wu, 2012), suggesting that its expression may suppress the tumorigenesis of these cancers and perhaps other cancer types (Wu, 2012).…”

Dual Roles of the Melanoma CAM (MelCAM/METCAM) in Malignant Progression of Melanoma

“…Alternatively, METCAM may behave differently from E-cadherin by being modulated by different cofactors or ligands, which are expressed at different stages of the cancer. The tumor suppressor role of METCAM is not restricted to the mouse melanoma K9 subline and it was first suggested in breast cancer cells [44]; however, the tumor suppression of METCAM in breast cancer cell lines could not be reproduced [45]. Recently we also found the tumor suppressor role of METCAM in two human ovarian cancer cell lines [46].…”

Immunophenotypic Characterization of Normal Bone Marrow Stem Cells

“…CD29 (integrin β 1 -subunit) and CD106 (vascular cell adhesion molecule 1, VCAM-1) seem to be important in the adhesion of MSC to endothelial cells Kolf et al, 2007;Stagg, 2007) and CD29, which when dimerized with CD49e (integrin α 5 -subunit) forms a receptor that binds to fibronectin and invasin, is likely to promote MSC-extracellular matrix interaction (Gu et al, 2009). CD146 (Muc18) plays an important role in cell-cell and cell-extracellular matrix adhesion and an increased expression of these marker on tumor cells is associated with an increased cell motility and invasiveness/ metastasis capability (Bardin et al, 2001;Zeng et al, 2011). The glycoprotein CD90 (Thy-1) regulates as well cell-cell and cell-extracellular matrix interactions, being involved in adhesion to endothelial cells, migration, metastasis and tissue regeneration (Jurisic et al, 2010;Rege & Hagood, 2006).…”