[Cu(<i>o</i>‑phthalate)(phenanthroline)] Exhibits Unique Superoxide-Mediated NCI-60 Chemotherapeutic Action through Genomic DNA Damage and Mitochondrial Dysfunction

The <i>in cellulo</i> catalytic production of reactive oxygen species (ROS) by copper­(II) and iron­(II) complexes is now recognized as a major mechanistic model in the design of effective cytotoxins of human cancer. The developmental complex, [Cu­(<i>o</i>-phthalate)­(1,10-phenanthroline)] (<b>Cu-Ph</b>), was recently reported as an intracellular ROS-active cytotoxic agent that induces double strand breaks in the genome of human cancer cells. In this work, we report the broad-spectrum action of <b>Cu-Ph</b> within the National Cancer Institute’s (NCI) Developmental Therapeutics Program (DTP), 60 human cancer cell line screen. The activity profile is compared to established clinical agentsvia the COMPARE algorithmand reveals a novel mode of action to existing metal-based therapeutics. In this study, we identify the mechanistic activity of <b>Cu-Ph</b> through a series of molecular biological studies that are compared directly to the clinical DNA intercalator and topoisomerase II poison doxorubicin. The presence of ROS-specific scavengers was employed for <i>in vitro</i> and intracellular evaluation of prevailing radical species responsible for DNA oxidation with superoxide identified as playing a critical role in this mechanism. The ROS targeting properties of <b>Cu-Ph</b> on mitochondrial membrane potential were investigated, which showed that it had comparable activity to the uncoupling ionophore, carbonyl cyanide <i>m</i>-chlorophenyl hydrazine. The induction and origins of apoptotic activation were probed through detection of Annexin V and the activation of initiator (8,9) and executioner caspases (3/7) and were structurally visualized using confocal microscopy. Results here confirm a unique radical-induced mechanistic profile with intracellular hallmarks of damage to both genomic DNA and mitochondria