A physiological role of interferon (IFN)-β derived from tumor: tumor growth of a mouse bladder carcinoma line MBT-2 is partially suppressed by autocrine IFN-β

Although some tumor cells endogenously produce a wide variety of cytokines, their physiological roles remain to be fully understood. In this study, we found that mouse subcutaneous tumor induced by inoculation of bladder tumor MBT-2 cells into syngeneic mice secreted a significant amount of interferon (IFN), whereas the cells exhibited no IFN production in in vitro cell culture. Typing experiment using IFN-specific neutralizing antibodies showed that the tumor-derived IFN was exclusively β type. Since the MBT-2 tumor tissues were homogenous and not infiltrated by immune cells, MBT-2 cells themselves were considered to be IFN-β producers. By intraperitoneal injection of neutralizing anti-IFN-β antibodies into MBT-2 cell-inoculated mice, the tumor growth was substantially precipitated and survival days of the tumor-bearing mice were shortened. As the in vitro cell growth of MBT-2 cells was dose-dependently inhibited by IFN-β, it was suggested that apparent immunogenicity of MBT-2 tumor is partially mediated by tumor suppression by autocrine IFN-β.