Mitochondria Determine the Efficacy of Anticancer Agents that Interact with DNA but Not the Cytoskeleton

Although chemotherapy is an important method for the treatment of patients with cancer, its efficacy is limited because of different sensitivities of tumor cells to anticancer agents and/or side effects on normal tissues. The present work demonstrates that mitochondria play a crucial role in the apoptosis of cancer cells induced by anticancer agents that interact with DNA but not with the cytoskeleton. Agents that interact with DNA selectively enhanced generation of reactive oxygen species (ROS) in mitochondria, released cytochrome c, and activated caspase-9 and caspase-3 to induce apoptosis of mesothelioma H2052 cells but not their rho(o) cells, which lack mitochondrial DNA (mtDNA). The sensitivity of a variety of cells to the agents showed positive correlation with the amounts of their mitochondria. In contrast, agents that selectively affect the cytoskeleton activated caspase-8 and caspase-3 and equally induced apoptosis of both H2052 and their rho(o) cells by a mitochondria-independent mechanism. The results suggest that mtDNA is a potential target for the anticancer agents that interact with DNA to induce ROS-dependent apoptosis of cancer cells, whereas agents that affect the cytoskeleton induce cell death by a mitochondria-and ROS-independent mechanism. The present observation is important for the selection of medicine for chemotherapy of patients with cancer.