418103 Enhancing Efficacy of Radiation Therapy through ROS Generation Catalyzed By Peptide-Conjugated Iron Oxide Nanoparticles

Thursday, November 12, 2015: 9:10 AM
253B (Salt Palace Convention Center)
Anastasia K. Hauser, Emily F. Daley, Kimberly W. Anderson and J. Zach Hilt, Chemical and Materials Engineering, University of Kentucky, Lexington, KY

Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer deaths in the United States. Radiation therapy is often used to treat NSCLC but can potentially result in serious side effects.  To increase the effectiveness of radiation, iron oxide nanoparticles (IONPs) can be utilized for their ability to produce reactive oxygen species (ROS). Cancer cells are more susceptible to oxidative insults compared to normal cells due to fast cell proliferation and metabolism. Additional ROS stress induced by exogenous agents can overwhelm the relatively low antioxidant capacity and disrupt the redox homeostasis inside cancer cells leading to selective tumor cell toxicity. IONPs increase ROS production within cancer cells by catalyzing the Haber-Weiss reaction which generates the highly reactive hydroxyl radical through Fenton chemistry. The Fenton reaction converts hydrogen peroxide to the hydroxyl radical via a reaction with iron ions. Previous work has shown that the surface of IONPs are approximately 50 times more efficient at catalyzing the Fenton reaction than free iron ions.  Radiation therapy promotes mitochondrial respiration which is often linked to higher cellular energy production. Increased respiration leads to an increase in mitochondrial production of the superoxide anion which is converted to hydrogen peroxide by superoxide dismutase. Iron oxide nanoparticles can then catalyze the reaction from hydrogen peroxide to the highly reactive hydroxyl radical. However, a significant limitation to this process is that IONPs are encapsulated within endosomes/lysosomes after internalization by a cell.  The hydroxyl radicals should be generated outside of the lysosomes to increase the probability of hydroxyl radical interaction with important organelles such as the mitochondria and the nucleus. Therefore, the aim of this project was to synthesize peptide conjugated IONPs that are able to escape the lysosomes after internalization by cancer cells. The peptide of interest, TAT, has been previously shown to facilitate nanoparticle escape from endosomes likely due to destabilization of the endosome membrane by its highly positive charge. A549 lung adenocarcinoma were exposed to TAT-conjugated IONPs, and confocal and electron microscopy were used to confirm the ability of TAT-IONPs to escape endosomes/lysosomes. Furthermore, the enhancement of ROS generation via the nuclear localizing IONPs was assessed using carboxy-DCF. Viability studies were also completed for A549 cells exposed to nuclear localizing IONPs with and without radiation treatments. Additionally, the oxygen consumption rate (OCR) was monitored for A549 cells after exposure to nuclear localizing IONPs with and without radiation using the Seahorse XF96 instrument. IONPs not conjugated with the nuclear localizing signal were used as controls for these studies. When combined with radiation, TAT-IONPs have the ability to increase ROS generation to higher levels than observed with radiation alone. When radiation treatment was combined with nuclear localizing IONPs, a synergistic cancer treatment resulted, meaning that the decrease in cell viability is greater than the two individual treatments. This enhancement was not observed for the IONP systems not conjugated with the nuclear localizing signal.  The presence of the TAT-IONPs also altered the OCR of A549 lung carcinoma with and without radiation treatment.

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