RT-40 * THE DOWN-REGULATION OF H-FERRITIN AS AN ADJUVANT THERAPY IN HUMAN GLIOMA

Abstract

Cancer cells generally exhibit increased iron requirements and heightened iron metabolism. As the major iron storage protein, ferritin expression is elevated in many types of cancer. In this study, we report that the sensitization of H-ferritin down-regulation in glioma cells against radiation and suggest the potential of H-ferritin down-regulation as an adjuvant therapy in human glioma. In human glioma cells, down-regulation of H-ferritin performed through a nanotechnology-based transfection platform led to a transient decrease in transferrin receptor level, suggesting a release of intracellular iron with loss of ferritin. This iron release in turn produced intracellular oxidative stress, demonstrated by protein oxidation damage, as well as a decrease in the stability of hypoxia-inducible factors (HIFs), which is an indicator of radioresistance. In glioma cells, exposure to radiation resulted in protein oxidation which could be exacerbated by H-ferritin down-regulation. Previously we have demonstrated a DNA protection role for H-ferritin. Here we expand this concept by showing that the down-regulation of H-ferritin is associated with increased DNA vulnerability when cells were exposed to ionizing radiation. The activation of DNA repair mechanisms was impaired when H-ferritin was absent. The in vitro data suggest a synergistic effect of radiation and H-ferritin down-regulation. Additionally, we expand our research into CD133-positive glioma stem cells (GSCs), which are notoriously resistant to anti-cancer treatment. Down-regulation of H-ferritin in GSCs inhibited cell proliferation in vitro, presumably through apoptosis induction. With an intracranial glioma model established by GSC implantation, we demonstrated that the survival was significantly prolonged by H-ferritin siRNA transfection through intravenous injection, in tumor bearing mice treated with first-line drug Temodar. This study supports the potential of H-ferritin siRNA as an adjuvant therapy in glioma treatment.