Enhanced cytotoxicity to lung cancer cells by mitochondrial delivery of camptothecin

Delivering traditional DNA-damaging anticancer drugs into mitochondria to damage mitochondria is a promising chemotherapy strategy. The impermeability of this mitochondrial inner membrane, however, impedes the delivery of drug molecules that could impact other important biological roles of mitochondria. Herein, the prodrug camptothecin (CPT)-triphenylphosphine (TPP) modified with hyaluronic acid (HA) via electrostatic adsorption (HA/CPT-TPP, HCT) was used to mediate the mitochondrial accumulation of CPT. These nanoparticles (NPs) showed enhanced drug accumulation in cancer cells through tumor targeting. HCT entered acidic lysosomes through endosomal transport, HA was degraded by hyaluronidase (HAase) in acidic lysosomes, and the positively charged CPT-TPP was exposed and accumulated fully in the mitochondria. Subsequently, CPT-TPP significantly disrupted the mitochondrial structure and damaged mitochondrial function, leading to increased reactive oxygen species (ROS) levels and energy depletion. Finally, HCT enhanced lung cancer cell apoptosis via the activation of caspase-3 and caspase-9. Furthermore, greatly increased tumor growth inhibition was observed in nude mice bearing A549 xenograft tumors after the administration of HCT via tail injection. This study demonstrated that the mitochondria-targeted delivery of CPT may be a promising antitumor therapeutic strategy.