title: Poorly differentiated colon carcinoma cell lines deficient in alpha-catenin expression express high levels of surface E-cadherin but lack Ca(2+)-dependent cell-cell adhesion.
abstract: Studies on several different types of carcinomas, with the notable exception of colon carcinoma, have shown that poorly differentiated tumors are frequently deficient in E-cadherin dependent cell-cell adhesion. In this study, we examined Ca(2+)-dependent cell-cell adhesion in colon carcinoma cell lines. Five poorly differentiated (Clone A, MIP 101, RKO, CCL 222, CCL 228) and four moderately-well differentiated (CX-1, CCL 235, DLD-2, CCL 187) colon carcinoma cell lines were assayed for their ability to form cell-cell aggregates and for their levels of E-cadherin expression. All of the poorly differentiated cell lines exhibited low levels of Ca(2+)-dependent cell-cell aggregation, in contrast to the moderately-well differentiated cell lines. Contrary to most previous studies, however, we observed that three of the five poorly differentiated cell lines examined expressed E-cadherin by FACS analysis and immunoprecipitation using an E-cadherin mAb. In fact, two of these cell lines expressed a 3- to 4-fold higher level of E-cadherin than that found in the moderately-well differentiated cell lines. mRNA levels for E-cadherin, as evaluated by both RT-PCR and Northern hybridization, corresponded to the levels of protein expression in each of the cell lines. Immunoprecipitation with an E-cadherin mAb, which is known to co-precipitate the catenins, demonstrated that the three poorly differentiated cell lines expressing E-cadherin did not co-precipitate alpha-catenin, although all of the moderately-well differentiated cell lines expressed both alpha- and beta-catenin. RT-PCR confirmed the absence of the alpha-catenin mRNA from two of these cell lines. Stable expression of an alpha-catenin cDNA in one of the poorly differentiated cell lines lacking alpha-catenin expression resulted in a 5-fold increase in its level of Ca(2+)-dependent cell-cell aggregation, providing evidence that alpha-catenin is directly responsible for the loss of cell-cell adhesion in some cell lines. The alpha-catenin transfectants also exhibited a marked reduction in migration on collagen I. These data indicate that loss of alpha-catenin expression, as well as E-cadherin expression, can lead to a phenotype associated with poorly differentiated colon carcinomas.
authors.affiliation: Laboratory of Cancer Biology, Deaconess Hospital, Harvard Medical School, Boston, MA 02115.
authors.forename: E
authors.initials: E
authors.lastname: Breen
authors.forename: A
authors.initials: A
authors.lastname: Clarke
authors.forename: G
authors.initials: G
authors.lastname: Steele
authors.forename: A M
authors.initials: AM
authors.lastname: Mercurio
mesh_terms: D001483:Base Sequence; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D002449:Cell Aggregation / Q000502:physiology; D002454:Cell Differentiation; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D003598:Cytoskeletal Proteins / Q000172:deficiency* / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology; D051178:alpha Catenin
chemical_list: C495273:CTNNA1 protein, human; D015820:Cadherins; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D004273:DNA, Neoplasm; D012333:RNA, Messenger; D051178:alpha Catenin; D002118:Calcium