Substrate mechanics and cell spreading.

Cell spreading and cell locomotion arise from forces exerted by actin microfilaments upon the substratum. Using modified protein films at fluorocarbon oil--water interfaces as substrates, we have measured some minimal mechanical properties required of these films to support cell spreading forces in vitro. For murine 3T3-L1 fibroblasts, complete cell spreading was obtained when the films exceeded surface shear moduli and surface fracture points of 15 and 5 dyne/cm, respectively. The human WI-38 fibroblast required more robust films than did its transformed counterpart (WI-38/VA 13) in order to achieve equivalent spreading. These results are of significance in understanding the metastatic capabilities of cancer cells.