Iron and reactive oxygen species: friends or foes of cancer cells?

SIGNIFICANCE: In this review, the dual nature of both iron and reactive oxygen species (ROS) will be explored in normal and cancer cell metabolism. Although iron and ROS play important roles in cellular homeostasis, they may also contribute to carcinogenesis. On the other hand, many studies have indicated that abrogation of iron metabolism, elevation of ROS, or modification of redox regulatory mechanisms in cancer cells, should be considered as therapeutic approaches for cancer. RECENT ADVANCES: Drugs that target different aspects of iron metabolism may be promising therapeutics for cancer. The ability of iron chelators to cause iron depletion and/or elevate ROS levels indicates that these types of compounds have more potential as antitumor medicines than originally expected. Other natural and synthetic compounds that target pathways involved in ROS homeostasis also have potential value alone or in combination with current chemotherapeutics. CRITICAL ISSUES: Although ROS induction and iron depletion may be targets for cancer therapies, the optimal therapeutic strategies have yet to be identified. This review highlights some of the research that strives to identify such therapeutics. FUTURE DIRECTIONS: More studies are needed to better understand the role of iron and ROS in carcinogenesis not only as cancer promoters, but also as cytotoxic agents to cancer cells and cancer stem cells (CSCs). Moreover, the structure-activity effects of iron chelators and other compounds that increase ROS and/or disrupt iron metabolism need to be further evaluated to assess the effectiveness and selectivity of these compounds against both cancer and CSCs.