Fibronectin and vitronectin adhesion enhancement during U937 cells differentiation induced by IL-6 and LIF

In this report the regulation of fibronectin, vitronectin, laminin and collagen type I receptors has been investigated during monocytic differentiation of U937 cells induced by two multifunctional cytokines, IL-6 and LIF. Our data show that the differentiation of U937 cells induced with both cytokines causes an increased adhesion to fibronectin and vitronectin. No changes in the adhesion to laminin and collagen type I were observed. Using immunofluorescence analysis we also demonstrated an inverse modulation of two fibronectin receptors, α4β1, which is down regulated and α5β1. This suggests that the two integrins play different roles during monocyte differentiation. An increased expression of αvβ3 vitronectin receptor during differentiation of U937 cells with both cytokines was observed. These findings indicate that IL-6 and LIF exert their effects on U937 cells maturation, at least partially, through the integrin regulation.