Abstract
The calcium-dependent cell-cell adhesion molecule E-cadherin has been shown to counteract invasion of epithelial neoplastic cells. Using three monoclonal antibodies, we have demonstrated the presence of E-cadherin at the surface of human MCF-7/6 mammary carcinoma cells by indirect immunofluorescence coupled to flow cytometry and by immunocytochemistry. Nevertheless, MCF-7/6 cells failed to aggregate in a medium containing 1.25 mM CaCl2, and they were invasive after confrontation with embryonic chick heart fragments in organ culture. Treatment of MCF-7/6 cells with 0.5 microgram ml-1 insulin-like growth factor I (IGF-I) led to homotypic aggregation within 5 to 10 min and inhibited invasion in vitro during at least 8 days. The effect of IGF-I on cellular aggregation was insensitive to cycloheximide. However, monoclonal antibodies that interfered with the function of either the IGF-I receptor (alpha IR3) or E-cadherin (HECD-1, MB2) blocked the effect of IGF-I on aggregation. The effects of IGF-I on aggregation and on invasion could be mimicked by 1 microgram ml-1 insulin, but not by 0.5 microgram ml-1 IGF-II. The insulin effects were presumably not mediated by the IGF-I receptor, since they could not be blocked by an antibody against this receptor (alpha IR3). Our results indicate that IGF-I activates the invasion suppressor role of E-cadherin in MCF-7/6 cells.
Highlights
We found that a variant of the MCF-7 human mammary carcinoma cell family, which did express Ecadherin at the cell surface, was invasive in vitro (Bracke et al, 1991) and in vivo (Correc et al, 1990)
Immunodetection of E-cadherin in MCF-7/6 cells Immunoblotting of MCF-7/6 cell extracts with anti-Ecadherin monoclonal antibodies (MB2, HECD-1 and monoclonal antibody against E-cadherin (MLCA)) revealed a 120-kD band, which is compatible with intact human E-cadherin (Figure 1)
Caco-2 colon carcinoma cells and MDA-MB-435 S/i mammary carcinoma cells served as control samples in which E-cadherin was respectively present and absent
Summary
MCF-7/6 is a variant of the human MCF-7 breast cancer cell family (Soule et al, 1973), obtained from Dr H. Received 10 February 1993; and in revised form 2 April 1993. (Unite d'Endocrinologie Cellulaire et Moleculaire, Montpellier, France). Biochemical, immunocytochemical and morphological data confirmed the MCF-7 origin of this cell line (Bracke et al, 1991; Coopman et al, 1991). The cell line was maintained in a mixture of Dulbecco's modification of Earle's Medium and Ham F12 (50:50; Flow, Irvine, Scotland), supplemented with 0.05% glutamine (w/v), 250 IU ml-' penicillin, 100 igml-' streptomycin and 10% foetal bovine serum (FBS)
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