Abstract
In previous studies, titanium peroxide nanoparticles (PAA-TiOx NPs) with surfaces functionalized using polyacrylic acid (PAA) and hydrogen peroxide (H2O2) demonstrated a synergistic effect when combined with X-ray irradiation. The combination generated H2O2 and reactive oxygen species (ROS) that enhanced the irradiation efficacy. In the present study, we examined the relationship between catalase and PAA-TiOx NPs sensitization to X-ray radiation because catalase is the primary antioxidant enzyme that converts H2O2 to water and oxygen. Catalase-knockout PANC-1 (dCAT) cells were generated using the CRISPR/Cas9 system, which was confirmed by the suppression of catalase expression in mRNA and protein levels that resulted in an 81.7% decrease in catalase activity compared with levels in wild-type cells. Catalase deficiency was found to increase the production of ROS, particularly in hypoxia. Also, the combination of PAA-TiOx NPs and X-ray 5 Gy resulted in a 7-fold decrease in the survival fraction (SF; p < 0.01) of dCAT cells compared with rates documented in wild-type cells. Interestingly, the combination treatment with X-ray 3 Gy in dCAT cells resulted in an SF similar to that observed in wild-type cells treated with the same combination but at a higher radiation dose (5 Gy). These results suggest that a strategy of catalase inhibition could be used to establish an advanced combination treatment of PAA-TiOx NPs and X-ray irradiation for pancreatic cancer cells.