REACTIVE OXYGEN SPECIES ACT AT BOTH TGF-BETA-DEPENDENT AND TGF-BETA-INDEPENDENT STEPS DURING INDUCTION OF APOPTOSIS OF TRANSFORMED-CELLS BYNORMAL-CELLS

We have recently shown that TGF-beta-treated normal fibroblasts can in duce apoptosis of transformed cells. The overall process was inhibited by antioxidants and radical scavengers, pointing to a role of reactiv e oxygen species (DOS). To define the ROS dependent steps precisely, o ur experimental system was dissected into three phases, During phase I , TGF-beta 1 induced production and release of apoptosis-inducing sign al molecules by normal cells. In phase II, these signal molecules were transferred between normal and transformed cells. During phase III, t ransformed cells went into apoptosis. The use of antibody directed aga inst TGF-beta revealed that TGF-beta was required only during phase I. Application of radical scavengers and antioxidants at defined phases revealed that reactive oxygen species are involved specifically with b iochemical processes induced by TGF-beta in normal cells and early in signal transfer between normal cells and transformed cells, These data therefore point to a functional role of reactive oxygen species both for the TGF-beta 1-induced signal pathway in normal cells and for the induction of apoptosis in transformed cells. (C) 1996 Academic Press, Inc.