bFGF stimulates U937 cell adhesion to fibronectin and secretion of gelatinase B

U937 cells are an immature monocytic cell line which has been used to study monocyte differentiation. For example, phorbol ester differentiation of U937 cells results in both an increase in adhesion to fibronectin through alpha 5 beta 1 integrin and the ability to degrade extracellular matrix (ECM) proteins through the secretion of gelatinase B (1, 2). The ability of monocytes to adhere to and degrade ECM molecules is fundamental to their localization at sites of inflammation and tissue damage. Here we find that bFGF treatment of U937 cells results in a six-fold increased adhesion to fibronectin. Further, monoclonal antibodies to alpha 5 or beta 1 integrin block the bFGF induced adhesion to fibronectin. bFGF also stimulated U937 cell secretion of a 92 kDa gelatinase which was identified by immunoblot to be gelatinase B. These data are the first to suggest a role for bFGF as an immunomodulatory factor during the early stages of inflammation.