Nifurtimox Enhances The Therapeutic Efficacy Of Radiation By Inducing Reactive Oxygen Species And Related Pathways: Pre-Clinical Study In Medulloblastoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Medulloblastoma (MB) is the most common malignant brain tumor in children, accounting for about 20% of pediatric CNS tumors. Multimodality treatments including surgery, radiotherapy (XRT) and chemotherapy have greatly improved disease outcome but survivors often suffer from deleterious effects of aggressive treatment with XRT. The aim of this study is to use novel strategies to enhance the response of XRT in a pre-clinical model for MB. XRT is known to cause DNA damage and cell death by inducing reactive oxygen species (ROS). Induction of ROS causes perturbation in antioxidant defense system thereby causing cell damage and death. Therefore, induction of ROS may serve as a promising strategy in cancer therapy. Nifurtimox (Nfx), a nitrofuran compound used to treat the parasitic infection Chagas’ disease, is known to induce ROS in pre-clinical models for neuroblastoma (NB) and MB. It is currently in clinical trials for treating NB and MB in children. In this study, we investigated the effects of Nfx in augmenting the efficacy of XRT in MB cell lines. DAOY and D283 cells were treated with varying dose of Nfx (5-70 µg/ml) or XRT (2-10 Gy) and cell viability was assessed using CellTiter-Glo for up to 5 days. The effect of combination therapy on cell viability, apoptosis, ROS levels and catalase activity was evaluated using optimized dose of Nfx and XRT. Results revealed that combination treatment significantly inhibited MB cell growth when compared to the effect of either Nfx or XRT alone. This was accompanied by the activation of apoptotic cell death as determined by increased annexin V staining and caspase 3/7 activity. An increase in ROS was also observed following combination treatment with Nfx and XRT which correlated with cell growth inhibition. Interestingly, catalase activity was unaltered following the treatment with single or double agents suggesting a contribution of impaired antioxidant system in causing MB cell growth inhibition. To further delineate the underlying mechanisms and to identify other candidates modulated by this combination therapy, we undertook molecular profiling approach using Affimetrix gene expression arrays (Human Gene 2.0 ST Array). We examined differentially expressed genes and affiliated pathways, and biological processes underlying tumor cell responses to Nfx and XRT. Our results identified genes that are statistically enriched for biological functions related to tumorigenesis, including cancer cell death and survival, cell cycle, and other functions relating to cancer disease. Several transcription factors and their downstream targets were also found to be enriched including the NRF2-mediated oxidative stress response pathway that responds to various stimuli including ROS. In conclusion, this pre-clinical study demonstrates that Nfx has the potential to enhance the therapeutic efficacy of radiation in MB cell lines. Citation Format: Don Eslin, Umesh T. Sankpal, Chris M. Lee, Giselle Saulnier Sholler, Robert M. Sutphin, Paul Bowman, Jeffrey C. Murray, Riyaz M. Basha. Nifurtimox enhances the therapeutic efficacy of radiation by inducing reactive oxygen species and related pathways: Pre-clinical study in medulloblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3382. doi:10.1158/1538-7445.AM2014-3382