Thermal sensitization through ROS modulation: A strategy to improve the efficacy of hyperthermic intraperitoneal chemotherapy

BackgroundThe purpose of this study was to investigate whether modulation of cellular reactive oxygen species (ROS) provides a synergistic effect with hyperthermia to induce tumor cell death in a colon cancer cell line.Materials and MethodsHT-29 colon cancer cells were exposed to heat (43°C) in the presence of the ROS-generating drug, 2-2′-azobis-(2-amidinopropane) dihydrochloride (AAPH) for 1 h. Viable cell mass and apoptosis was measured by MTT and annexin V staining, respectively. Oxidative stress was evaluated by DCFH fluorescence. Protein levels were determined by Western blot analysis.ResultsA synergistic effect on cell viability with AAPH was noted under hyperthermic conditions as compared with hyperthermia alone (P < .05). The number of nonviable cells after hyperthermia and AAPH exposure was also significantly increased compared with AAPH at 37°C (42% vs 20%, P < .05). ROS levels were increased modestly with AAPH at 37°C, whereas they increased significantly in a dose-dependent manner with AAPH at 43°C. Transient increases of phosphorylated-p38 and ERK and decreases in phosphorylated-AKT were observed in the cells exposed to AAPH at 43°C. Pretreatment of inhibitors of p38 yielded additional decreases in cell mass when used in combination with AAPH and hyperthermia (P < .05). Increased expression of HSP 27 observed at 43°C was abrogated with AAPH exposure.ConclusionsOxidative stress increased the cytotoxic effects of hyperthermia in colon cancer cells. Thermal sensitization through modulation of cellular ROS may represent a novel approach to increase the efficacy of hyperthermia as an anticancer modality.