Exogenous fibronectin requirement for adhesion by neoplastic human cells.

We have studied the effect of serum, plasma and plasma fibronectin on the spreading behavior of several normal and neoplastic human cells using a quantitative spreading assay. Normal human cells are rich in surface fibronectin and are able to spread in the absence of serum or exogenous fibronectin. Virus-transformed cells and cells of neoplastic origin have reduced or no recognizable surface fibronectin and are dependent on serum or plasma for spreading. In agreement with previous studies on rodent cells, fibronectin appears to be the major factor responsible for this effect. Neoplastic cells can spread on fibronectin-coated substrata or can recruit fibronectin directly from the medium. The capacity of transformed cells to recruit fibronectin from the medium correlates with the presence of intercellular fibronectin as seen by the immunofluorescence technique on monolayer cultures. Our results are in keeping with the concept that neoplastic cells may be dependent on extracellular fibronectin for adherence in vivo and that this dependency may vary between different cell types.