title: IGF-I receptor-induced cell-cell adhesion of MCF-7 breast cancer cells requires the expression of junction protein ZO-1.
abstract: Hyperactivation of the insulin-like growth factor I receptor (IGF-IR) contributes to primary breast cancer development, but the role of the IGF-IR in tumor metastasis is unclear. Here we studied the effects of the IGF-IR on intercellular connections mediated by the major epithelial adhesion protein, E-cadherin (E-cad). We found that IGF-IR overexpression markedly stimulated aggregation in E-cad-positive MCF-7 breast cancer cells, but not in E-cad-negative MDA-MB-231 cells. However, when the IGF-IR and E-cad were co-expressed in MDA-MB-231 cells, cell-cell adhesion was substantially increased. The IGF-IR-dependent cell-cell adhesion of MCF-7 cells was not related to altered expression of E-cad or alpha-, beta-, or gamma-catenins but coincided with the up-regulation of another element of the E-cad complex, zonula occludens-1 (ZO-1). ZO-1 expression (mRNA and protein) was induced by IGF-I and was blocked in MCF-7 cells with a tyrosine kinase-defective IGF-IR mutant. By co-immunoprecipitation, we found that ZO-1 associates with the E-cad complex and the IGF-IR. High levels of ZO-1 coincided with an increased IGF-IR/alpha-catenin/ZO-1-binding and improved ZO-1/actin association, whereas down-regulation of ZO-1 by the expression of an anti-ZO-1 RNA inhibited IGF-IR-dependent cell-cell adhesion. The results suggested that one of the mechanisms by which the activated IGF-IR regulates E-cad-mediated cell-cell adhesion is overexpression of ZO-1 and the resulting stronger connections between the E-cad complex and the actin cytoskeleton. We hypothesize that in E-cad-positive cells, the IGF-IR may produce antimetastatic effects.
authors.affiliation: Kimmel Cancer Center, Thomas Jefferson University, 233 S. 10th St., Philadelphia, PA 19107, USA.
authors.forename: L
authors.initials: L
authors.lastname: Mauro
authors.forename: M
authors.initials: M
authors.lastname: Bartucci
authors.forename: C
authors.initials: C
authors.lastname: Morelli
authors.forename: S
authors.initials: S
authors.lastname: Andò
authors.forename: E
authors.initials: E
authors.lastname: Surmacz
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D015820:Cadherins / Q000378:metabolism*; D002448:Cell Adhesion; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007365:Intercellular Junctions; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: D015820:Cadherins; D008565:Membrane Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D017526:Receptor, IGF Type 1