Truncation of the extracellular region abrogrates cell contact but retains the growth-suppressive activity of E-cadherin.
E-cadherin has been demonstrated to induce growth suppression and decrease the invasiveness of cancer cells and thus has been proposed to be a tumor suppressor gene. The ability of E-cadherin to mediate cell-cell contact and contact inhibition presumably accounts for its antitumor effects, which are attributed to the extracellular domain of the protein. Here we report that blocking the ability of E-cadherin to mediate contact inhibition by either antagonistic antibodies or expression of a mutant form of E-cadherin with the extracellular region deleted does not abrogate growth suppression. Transfection of the E-cadherin gene into the human prostate cancer cell line TSU.Pr-1 induced cell-cell contact formation, growth suppression, and redistribution of beta-catenin to the cell membrane. Treatment of the E-cadherin transfectant (CAD) with blocking antibodies disrupted cell-cell contact formation but did not influence the growth rate, suggesting that cell-cell interaction is not required for E-cadherin-mediated growth suppression. Similarly, transfection of an E-cadherin construct in which the NH2-terminal (extracellular) region was deleted did not allow cell-cell contact formation but induced growth suppression. In contrast, transfection of an E-cadherin construct in which the COOH-terminal (cytoplasmic) region was deleted did not induce suppression but promoted cell contact formation. In cells expressing E-cadherin lacking the cytoplasmic region, beta-catenin was evenly distributed in the cytoplasm. By contrast, in cells expressing E-cadherin lacking the extracellular region, beta-catenin was cell membrane associated. Growth suppression was always associated with the localization of beta-catenin to the cell membrane. The redistribution of beta-catenin from the cytoplasm to the cell membrane initially suggested the involvement of the Wnt signaling pathway in regulating cell growth. However, only small differences in beta-catenin/T-cell factor signaling were detected in control and E-cadherin-expressing cells, suggesting that the Wnt pathway is not involved. Taken together, these findings suggest that E-cadherin-induced growth inhibition may not be solely attributed to contact inhibition but may involve the redistribution of beta-catenin from the cytoplasm to the cell membrane, and this redistribution may affect growth pathways independent of T-cell factor.
Sasaki
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CY
Laboratories of Immunology, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA.
Lin
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Morin
P J
PJ
Longo
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DL
D000818:Animals; D015820:Cadherins / Q000737:chemistry* / Q000235:genetics*; D002448:Cell Adhesion; D002450:Cell Communication; D002455:Cell Division / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents / Q000494:pharmacology; D003260:Contact Inhibition; D003593:Cytoplasm / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019084:Fluorescent Antibody Technique, Indirect; D017930:Genes, Reporter; D015151:Immunoblotting; D008297:Male; D051379:Mice; D009154:Mutation; D009369:Neoplasms / Q000378:metabolism*; D011233:Precipitin Tests; D011471:Prostatic Neoplasms / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D015534:Trans-Activators; D014158:Transcription, Genetic; D014162:Transfection; D051178:alpha Catenin; D051176:beta Catenin
C495267:CTNNB1 protein, mouse; D015820:Cadherins; D004396:Coloring Agents; C495272:Ctnna1 protein, mouse; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D013778:Tetrazolium Salts; D013844:Thiazoles; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; C022616:thiazolyl blue