Role of plasma fibronectin in the morphological transformation of hamster embryo cells.

Replacement of fetal bovine serum (FBS) by newborn serum in the hamster embryo cell transformation assay blocks the induction of morphologically transformed colonies by chemical carcinogens. Moreover, the addition of newborn serum strongly inhibits the formation of morphologically transformed colonies in the standard assay using 20% FBS. The present experiments show that the inhibitory factor is heat labile and not dialyzable, but is removed when the newborn serum is submitted to gelatin affinity chromatography. The inhibitory factor is recovered in the eluted gelatin bound material which gives essentially one band in SDS electrophoresis corresponding to that of plasma fibronectin. In separate experiments fibronectin from bovine plasma is shown to inhibit cell transformation in a similar way. The experiments suggest that fibronectin plays a central role in the mechanism of morphological cell transformation.