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Epithelial cell adhesion molecule (Ep-CAM) modulates cell-cell interactions mediated by classic cadherins.

Litvinov SV, Balzar M, Winter MJ, Bakker HA, Briaire-de Bruijn IH, Prins F, Fleuren GJ, Warnaar SO - J. Cell Biol. (1997)

Bottom Line: Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM.While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases.The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Leiden University, Leiden 2300 RC, The Netherlands. slitvinov@pathology.medfac.leidenuniv.nl

ABSTRACT
The contribution of noncadherin-type, Ca2+-independent cell-cell adhesion molecules to the organization of epithelial tissues is, as yet, unclear. A homophilic, epithelial Ca2+-independent adhesion molecule (Ep-CAM) is expressed in most epithelia, benign or malignant proliferative lesions, or during embryogenesis. Here we demonstrate that ectopic Ep-CAM, when expressed in cells interconnected by classic cadherins (E- or N-cadherin), induces segregation of the transfectants from the parental cell type in coaggregation assays and in cultured mixed aggregates, respectively. In the latter assay, Ep-CAM-positive transfectants behave like cells with a decreased strength of cell-cell adhesion as compared to the parental cells. Using transfectants with an inducible Ep-CAM-cDNA construct, we demonstrate that increasing expression of Ep-CAM in cadherin-positive cells leads to the gradual abrogation of adherens junctions. Overexpression of Ep-CAM has no influence on the total amount of cellular cadherin, but affects the interaction of cadherins with the cytoskeleton since a substantial decrease in the detergent-insoluble fraction of cadherin molecules was observed. Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM. While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases. As the cadherin-mediated cell-cell adhesions diminish, Ep-CAM-mediated intercellular connections become predominant. An adhesion-defective mutant of Ep-CAM lacking the cytoplasmic domain has no effect on the cadherin-mediated cell-cell adhesions. The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

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Changes in subcellular distribution of cadherins in HCA cells upon expression of Ep-CAM. HCA  cells transfected with inducible pMEp4 vector, either  blank (HMC) or containing  the Ep-CAM cDNA (Wt),  were induced with 50 μM  CdCl2 24 h before fixation,  fixed, and stained with anti-pan cadherin mAb CH-19  (reacts mainly with N-cadherin, the major cadherin of  HCA cells). Note the redistribution of cadherins from  adherens junctions to free  domains of cell membrane in  Wt Ep-CAM transfectants,  and a general shift of the cell  phenotype to a more scattered one. Bar, 5 μm.
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Figure 11: Changes in subcellular distribution of cadherins in HCA cells upon expression of Ep-CAM. HCA cells transfected with inducible pMEp4 vector, either blank (HMC) or containing the Ep-CAM cDNA (Wt), were induced with 50 μM CdCl2 24 h before fixation, fixed, and stained with anti-pan cadherin mAb CH-19 (reacts mainly with N-cadherin, the major cadherin of HCA cells). Note the redistribution of cadherins from adherens junctions to free domains of cell membrane in Wt Ep-CAM transfectants, and a general shift of the cell phenotype to a more scattered one. Bar, 5 μm.

Mentions: At the basal level of Ep-CAM expression, the morphology of Ep-CAM transfectants in cell culture was quite similar to the control cells transfected with the blank vector. However, induction of high levels of Ep-CAM resulted in loss of the polygonal morphology and in a more scattered phenotype, although the cells still remained attached to one another (Fig. 11). This change in morphology was observed for the entire cell population only at the highest (50 μM) concentration of Cd2+ tested, although some of these changes could be observed for some cells or groups of cells at lower concentrations of Cd2+ (2–5 μM), with changes increasing proportionally to the Ep-CAM levels. The effect was reversible, and within 3 d of culture in the absence of the Cd2+ in the medium, the cells regained their original morphology, consistent with the decrease of Ep-CAM levels back to that of noninduced cells (flow cytometry data, not shown).


Epithelial cell adhesion molecule (Ep-CAM) modulates cell-cell interactions mediated by classic cadherins.

Litvinov SV, Balzar M, Winter MJ, Bakker HA, Briaire-de Bruijn IH, Prins F, Fleuren GJ, Warnaar SO - J. Cell Biol. (1997)

Changes in subcellular distribution of cadherins in HCA cells upon expression of Ep-CAM. HCA  cells transfected with inducible pMEp4 vector, either  blank (HMC) or containing  the Ep-CAM cDNA (Wt),  were induced with 50 μM  CdCl2 24 h before fixation,  fixed, and stained with anti-pan cadherin mAb CH-19  (reacts mainly with N-cadherin, the major cadherin of  HCA cells). Note the redistribution of cadherins from  adherens junctions to free  domains of cell membrane in  Wt Ep-CAM transfectants,  and a general shift of the cell  phenotype to a more scattered one. Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2140211&req=5

Figure 11: Changes in subcellular distribution of cadherins in HCA cells upon expression of Ep-CAM. HCA cells transfected with inducible pMEp4 vector, either blank (HMC) or containing the Ep-CAM cDNA (Wt), were induced with 50 μM CdCl2 24 h before fixation, fixed, and stained with anti-pan cadherin mAb CH-19 (reacts mainly with N-cadherin, the major cadherin of HCA cells). Note the redistribution of cadherins from adherens junctions to free domains of cell membrane in Wt Ep-CAM transfectants, and a general shift of the cell phenotype to a more scattered one. Bar, 5 μm.
Mentions: At the basal level of Ep-CAM expression, the morphology of Ep-CAM transfectants in cell culture was quite similar to the control cells transfected with the blank vector. However, induction of high levels of Ep-CAM resulted in loss of the polygonal morphology and in a more scattered phenotype, although the cells still remained attached to one another (Fig. 11). This change in morphology was observed for the entire cell population only at the highest (50 μM) concentration of Cd2+ tested, although some of these changes could be observed for some cells or groups of cells at lower concentrations of Cd2+ (2–5 μM), with changes increasing proportionally to the Ep-CAM levels. The effect was reversible, and within 3 d of culture in the absence of the Cd2+ in the medium, the cells regained their original morphology, consistent with the decrease of Ep-CAM levels back to that of noninduced cells (flow cytometry data, not shown).

Bottom Line: Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM.While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases.The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Leiden University, Leiden 2300 RC, The Netherlands. slitvinov@pathology.medfac.leidenuniv.nl

ABSTRACT
The contribution of noncadherin-type, Ca2+-independent cell-cell adhesion molecules to the organization of epithelial tissues is, as yet, unclear. A homophilic, epithelial Ca2+-independent adhesion molecule (Ep-CAM) is expressed in most epithelia, benign or malignant proliferative lesions, or during embryogenesis. Here we demonstrate that ectopic Ep-CAM, when expressed in cells interconnected by classic cadherins (E- or N-cadherin), induces segregation of the transfectants from the parental cell type in coaggregation assays and in cultured mixed aggregates, respectively. In the latter assay, Ep-CAM-positive transfectants behave like cells with a decreased strength of cell-cell adhesion as compared to the parental cells. Using transfectants with an inducible Ep-CAM-cDNA construct, we demonstrate that increasing expression of Ep-CAM in cadherin-positive cells leads to the gradual abrogation of adherens junctions. Overexpression of Ep-CAM has no influence on the total amount of cellular cadherin, but affects the interaction of cadherins with the cytoskeleton since a substantial decrease in the detergent-insoluble fraction of cadherin molecules was observed. Similarly, the detergent-insoluble fractions of alpha- and beta-catenins decreased in cells overexpressing Ep-CAM. While the total beta-catenin content remains unchanged, a reduction in total cellular alpha-catenin is observed as Ep-CAM expression increases. As the cadherin-mediated cell-cell adhesions diminish, Ep-CAM-mediated intercellular connections become predominant. An adhesion-defective mutant of Ep-CAM lacking the cytoplasmic domain has no effect on the cadherin-mediated cell-cell adhesions. The ability of Ep-CAM to modulate the cadherin-mediated cell-cell interactions, as demonstrated in the present study, suggests a role for this molecule in development of the proliferative, and probably malignant, phenotype of epithelial cells, since an increase of Ep-CAM expression was observed in vivo in association with hyperplastic and malignant proliferation of epithelial cells.

Show MeSH
Related in: MedlinePlus