Adhesion of cells to cleaved OPN. Adhesion assays were performed with two different cell types to surfaces coated with 5 pmol of full-length OPN or protease-cleaved human milk. OPN is referred to as OPN (full-length), nOPN (mixture of purified N-terminal fragments), OPN+PL (OPN cleaved with plasmin), OPN+TH (OPN cleaved with thrombin), and OPN+CD (OPN cleaved with cathepsin D). Bars show mean values for three wells per protein ± S.D. Data shown are representative of three independent experiments for each cell line. Adhesion to 1% bovine serum albumin was used as background and was subtracted from all values. A, adhesion of MDA-MB-435 cells to surfaces coated with the specified OPN forms. B, adhesion of MDA-MB-435 cells to wells coated with OPN after preincubation in the presence or absence of an antibody against the αVβ3-integrin or an isotype IgG control (5 μg/ml). C, adhesion of K562 cells to surfaces coated with the specified OPN forms. D, adhesion of K562 cells to wells coated with OPN after preincubation in the presence or absence of an antibody against the α5β1-integrin or an isotype IgG control (5 μg/ml).