Drug Repurposing: An Avenue Toward Stress Medicine in Cancer Therapy

Cancer cells harbor a higher level of radical species owing to the metabolic reprogramming and signaling aberrations required for the continuously uncontrolled proliferation. The high basal level of reactive oxygen species (ROS) in cancer cells renders them more susceptible to reagents that further augment ROS generation or that weaken antioxidant defenses, proposing that the augment of oxidative stress exclusively in cancer cells provides a rational therapeutic strategy for anticancer drug development. Taking advantage of an attractive strategy termed drug repurposing, which describes identifying new medical indications for existing drugs with less risk, lower cost, and shorter development timeline, a portfolio of non-oncology drugs with the potential of boosting oxidative stress is repurposed to extend the arsenal of cancer therapies. In this chapter, we will present the growing data that repurposing of old drugs, especially agents modulating oxidative stress, for anticancer activity, provides an opportunity to rapidly advance therapeutic strategies into clinical trials at a relatively low cost.