FIG. 4.

Chemical cross-linking inhibits proteolytic removal of fibronectin. v-src-transformed CEF were plated on fibronectin-coated or chemically cross-linked fibronectin-coated cover glasses. (A) Cells plated for 48 h on cross-linked fibronectin and stained with HFN7.1 monoclonal antibody showing diffuse staining of the initial human fibronectin. (B) Same field as panel A but stained with ethidium homodimer. (C) Cells plated on normal fibronectin for 48 h and stained with HFN7.1 showing that most of the fibronectin has been removed by the cells. (D) Same field as panel C but stained with ethidium homodimer. (E and F) Quantification of residual fibronectin levels after 48 h by using HFN7.1 antibody (E) or rabbit anti-fibronectin (F). Fn, fibronectin only; X-Fn, cross-linked fibronectin only; Fn-C, fibronectin plus transformed cells; X-Fn-C, cross-linked fibronectin plus transformed cells. (G and H) Modified enzyme-linked immunosorbent assay showing the removal of normal (●) or cross-linked (○) fibronectin by transformed cells as a function of fibronectin density by using HFN7.1 antibody (G) and rabbit anti-fibronectin antibody (H). Error bars indicate the standard deviation (n = 3).