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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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The internal structure of the large aggregates formed  by LEC-MC and LEC-MEp.6 cells in 24 h of suspension culture.  The expression of Ep-CAM in LEC-MEp.6 cells was induced with  10 μM CdCl2 for 24 h before the aggregation assay (+). The aggregates were fixed with 2% paraformaldehyde/1.25% glutaraldehyde, embedded into Epon, and ultrathin sectioned. Sections  were analyzed by reflection contrast microscopy. Bar, 25 μm.
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Figure 5: The internal structure of the large aggregates formed by LEC-MC and LEC-MEp.6 cells in 24 h of suspension culture. The expression of Ep-CAM in LEC-MEp.6 cells was induced with 10 μM CdCl2 for 24 h before the aggregation assay (+). The aggregates were fixed with 2% paraformaldehyde/1.25% glutaraldehyde, embedded into Epon, and ultrathin sectioned. Sections were analyzed by reflection contrast microscopy. Bar, 25 μm.

Mentions: Over time (⩽24 h of suspension culture), even the induced LEC-MEp.6 cells were able to form some larger multicellular aggregates. However, the internal structure of these aggregates differed substantially as compared to aggregates of LEC-MC cells, with the latter consisting of tightly interconnected cells, whereas the cells in LEC-MEp.6 aggregates had only sporadic connections (Fig. 5). This argues against the hypothesis that the expression of Ep-CAM simply delayed, rather than inhibited, the E-cadherin–mediated cell aggregation, as the loose interconnection of cells in LEC-Mep.6 aggregates clearly points to a reduction in the number of the E-cadherin–mediated intercellular adhesions.


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)

The internal structure of the large aggregates formed  by LEC-MC and LEC-MEp.6 cells in 24 h of suspension culture.  The expression of Ep-CAM in LEC-MEp.6 cells was induced with  10 μM CdCl2 for 24 h before the aggregation assay (+). The aggregates were fixed with 2% paraformaldehyde/1.25% glutaraldehyde, embedded into Epon, and ultrathin sectioned. Sections  were analyzed by reflection contrast microscopy. Bar, 25 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: The internal structure of the large aggregates formed by LEC-MC and LEC-MEp.6 cells in 24 h of suspension culture. The expression of Ep-CAM in LEC-MEp.6 cells was induced with 10 μM CdCl2 for 24 h before the aggregation assay (+). The aggregates were fixed with 2% paraformaldehyde/1.25% glutaraldehyde, embedded into Epon, and ultrathin sectioned. Sections were analyzed by reflection contrast microscopy. Bar, 25 μm.
Mentions: Over time (⩽24 h of suspension culture), even the induced LEC-MEp.6 cells were able to form some larger multicellular aggregates. However, the internal structure of these aggregates differed substantially as compared to aggregates of LEC-MC cells, with the latter consisting of tightly interconnected cells, whereas the cells in LEC-MEp.6 aggregates had only sporadic connections (Fig. 5). This argues against the hypothesis that the expression of Ep-CAM simply delayed, rather than inhibited, the E-cadherin–mediated cell aggregation, as the loose interconnection of cells in LEC-Mep.6 aggregates clearly points to a reduction in the number of the E-cadherin–mediated intercellular adhesions.

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