Effect of Fibronectin to Macrophage for Destruction of MBT-2 Cell

Seo, Il Young; Rim, Joung Sik; Chung, Hun Taeg

Abstract

Fibronectin(Fn) is a large, multidomain glycoprotein, which exists in a soluble form in plasma and an insoluble fibrillar form in extracellular matrices. Fn affects many aspects of cellular responses. However, it is not known whether Fn could activate macrophages for the tumor cell killing. We report that Fn induces the tumoricidal activity of macrophages for murine bladder tumor(MBT-2) cell. Tumoricidal activity was determined by 3[H]-thymidine uptake of MBT-2 cell. Fn alone had no effect, whereas recombinant interferon- r(IFN- r) weakly induced the tumoricidal activity of macrophages for MBT-2 cells. However combination of Fn with recombinant IFN-r synergized to activate macrophages to kill MBT-2 cells in a dose dependent manner. At this point nitric oxide(NO) was secreted by activated macrophages, and the secretion of NO and tumoricidal activity of macrophage were inhibited in the presence of NG-monomethyl- L-arginine(NGMMA), a competitive inhibitor of NO synthase(NOS). Fn has various cell binding sites. The Arg-Gly-Asp(RGD) sequence present in the central cell binding domain of Fn is the prototype of these sites. Engineered fibronectin(eFn) is formed by RGD-rich sequence. Combination of eFn, instead of Fn, with recombinant IFN- T resulted in more powerful activation of macrophage in tumor cell killing than Fn. In conclusion, our results demonstrate that Fn acts as a modulator of macrophage activation for tumor cell killing induced by IFN-r via a process involving L-arginine dependent NO production. Especially, RGD sequence of Fn has important role for tumoricidal activity of macrophage. Although the precise mechanism of Fn to promote NO synthesis induced by IFN-r remains to be further elucidated, Fn-mediated macrophage adhesion by specialized cell surface receptors and activation of intracellular signals might be important in the development of macrophage activation.