Role of serum in protease-induced stimulation of 3T3 cell division past the monolayer stage

Abstract

TREATMENT of a confluent, quiescent 3T3 mouse embryo fibroblast cell monolayer with low concentrations of various proteases is sufficient to induce a new round of cell division^1,2. It was suggested that modification of the 3T3 surface conformation from the non-agglutinable to the agglutinable state after protease treatment might have been responsible for the initiation of this round of cell division. More recently, however, Glynn et al.³ demonstrated that modification of the 3T3 cell surface from the agglutinable to the non-agglutinable state was not sufficient in itself to induce a new round of cell division. In the light of this and other unpublished work from our laboratory I have re-evaluated the role of various culture conditions in the induction of 3T3 cell division after a brief treatment with Pronase. I found that induction of cell division after treatment of a confluent 3T3 monolayer with protease depends both qualitatively and quantitatively on the serum in the growth medium and that this requirement varies from cell line to cell line. Furthermore, my results suggest that the modification in surface architecture detected as enhanced agglutinability after brief proteolysis is not sufficient to induce a new round of cell division.