Prospective strategies to enforce selectively cell death in cancer cells.

Although induction of apoptosis (cell death mediated by caspases) determines response to cancer therapy, this approach is limited by lack of selectivity in available apoptosis-inducing agents. Furthermore, most cancers, almost by definition, are resistant to apoptosis, growth arrest and cell senescence. Then, how can anticancer agents kill cancer cell without unacceptable toxicity to a patient? The potential therapeutic approaches range from selective inhibition of antiapoptotic pathways, antiangiogenic therapy, tissue-selective therapy (including immunotherapy) to exploitation of, for example, drug resistance, oncoprotein addiction, unrestricted cell cycles, hypermitogenic and hypoxic features of cancer cells. These overlapping and complementary approaches rely on rational drug combinations (at mechanism-based doses and sequences) aimed at matching targets. To ensure killing of cancer cells selectively, we may combine apoptosis- and senescence-inducing agents with inhibitors of apoptosis (to protect normal cells), inhibitors of signal transduction with cell cycle-dependent chemotherapy, antiangiogenic agents with hypoxia-inducible factor-1 inhibitors, tissue-selective therapy with differentiating agents and activators of death receptors with chemotherapy. In theory, consecutive use of these drug combinations may control cancer.