Direct evidence that iron deprivation induces apoptosis in murine lymphoma 38C13

We found that the mouse B cell lymphoma 38C13 underwent apoptosis in vitro when deprived of iron by three independent methods: (1) exposure to a synergistic pair of rat IgG monoclonal antibodies against the mouse transferrin receptor; (2) exposure to the iron chelator deferoxamine (DFO), and (3) exposure to a defined culture medium without any added iron (iron-poor medium). When each antibody was present at a concentration of 5 mu g/ml, the number of living cells declined to approximately 25% after a 24-hour incubation. After 48 h, there were no surviving cells. When DFO was present at a concentration of 10 mu M, the effects were similar, but delayed by 24 h. When iron-poor medium was used, the effects and kinetics were similar to those seen with antibody treatment. For each method of iron deprivation, the reduction in cell viability correlated with the development of apoptosis, as assessed by DNA fragmentation analysis and propidium iodide staining. Electron microscopy studies provided additional confirmation of apoptotic cell death. The addition of 500 mu M ferric citrate completely prevented apoptosis for each of the three methods of iron deprivation. These studies provide new and compelling evidence to support the view that iron deprivation can specifically induce apoptosis and serve to strengthen the rationale for further studies of iron deprivation as a form of cancer treatment.