REMOVAL OF SIALIC-ACID FROM THE SURFACE OF HUMAN MCF-7 MAMMARY-CANCERCELLS ABOLISHES E-CADHERIN-DEPENDENT CELL-CELL ADHESION IN AN AGGREGATION ASSAY

MCF-7 human breast cancer cells express E-cadherin and show, at least in some circumstances, E-cadherin-dependent cell-cell adhesion (Bracke et al., 1993). The MCF-7/AZ variant spontaneously displays E-cadherin -dependent fast aggregation; in the MCF-7/6 variant, E-cadherin appear ed not to be spontaneously functional in the conditions of the fast ag gregation assay, but function could be induced by incubation of the su spended cells in the presence of insulinlike growth factor I (IGF-I) ( Bracke et al., 1993). E-cadherin from MCF-7 cells was shown to contain sialic acid. Treatment with neuraminidase was shown to remove this si alic acid, as well as most of the sialic acid present at the cell surf ace. Applied to MCF-7/AZ, and MCF-7/6 cells, pretreatment with neurami nidase abolished spontaneous as well as IGF-I induced, E-cadherin-depe ndent fast cell-cell adhesion of cells in suspension, as measured in t he fast aggregation assay. Treatment with neuraminidase did not, howev er, inhibit the possibly different, but equally E-cadherin-mediated, p rocess of cell-cell adhesion of MCF-7 cells on a flat plastic substrat e as assessed by determining the percentage of cells remaining isolate d (without contact with other cells) 24 h after plating.