The biological effect of introduction of OPN into benign R37 cells. A Immunoblot showing OPN protein levels in R37, R37-pBK-CMV and R37-OPN cells. Cell lysates were diluted and 20 μg loaded onto a SDS 10% (w/w) polyacrylamide gel as follows: lane 1 R37; lane 2; R37-pBK-CMV; lane 3 R37-OPN. Specific proteins were detected using antibodies to OPN and β-actin. Bands were quantified using densitometric analysis and normalized against β-actin. The average fold increase for three different experiments are: lane 1 = 1, lane 2 = 1 ± 0.2 and lane 3 = 10 ± 1.7. B Ability of transfected cell lines to adhere to a fibronectin-treated surface was assessed over a 30 min period and the number of adherent cells quantified. Results of the mean ± standard error from three independent experiments are shown. C Soft agar assay was carried out to assess the ability of stably transfected cell lines to grow in an anchorage independent environment. The colony number was assessed after 5 days. Results of the mean ± standard error from three independent experiments are shown. D R37, R37-pBK-CMV and R37-OPN were plated on ECM-coated filters (500 μg/ml) in Boyden chambers. The number of cells that migrated through the filter after 48 hrs was determined by staining and scanning using a digital imaging system (Methods). Results of the mean ± standard error from three independent experiments are shown.