Targeting cancer cells by exploiting their resistance.

Cancer cells are intrinsically resistant to growth arrest and can further acquire multidrug resistance. Current approaches to this problem are intended to reverse, overcome or prevent the drug resistance. However, the resistance of cancer cells can be exploited to kill resistant cells selectively, while sparing sensitive normal cells. As the simplest example, multidrug-resistant cells pump out protectors, such as pharmacological inhibitors of apoptosis. A sequence of at least two agents must include an exclusive protector, which is ineffective in resistant cancer cells, and an inclusive cytotoxic drug, which kills unprotected cells. By abolishing several dose-limiting side effects of chemotherapy, this strategy provides a means to treat selectively most deranged, aggressive and resistant cancers.