Mechanisms of Synergistic Effect Between Nanosecond Electric Pulse and Nonthermal Plasma to Treat Pancreatic Cancer

Abstract

Pancreatic cancer is a significant cause of cancer-associated mortality. Currently, prevention or early diagnosis at a curable stage is exceedingly difficult. The standard of care is surgery, chemotherapy, and radiation therapy, which are largely ineffective against late-stage pancreatic cancer. New effective therapeutics or drugs are desperately needed for this deadly disease. We previously reported that nanosecond electric pulses (nsEP) could be an effective therapy to treat pancreatic cancer in animal models. However, owing to the demand for high-intensive electric fields, all currently available designs of nsEP delivery systems can only treat small tumors (4-7 mm). To overcome this hurdle, we propose a combination of nsEP with non-thermal plasma (NTP) to treat large tumors with clinically relevant sizes. Previously, we reported that a synergistic effect resulted from moderate nsEP and NTP dosages to treat Pan02 pancreatic cancer cells. In this study we designed experiments to further determine the underlying mechanism. The role of reactive oxygen species (ROS) in cell death and its relation to mitochondrial membrane potential drop were analyzed by flow cytometry and fluorescence microscopy. We demonstrated that ROS generation was nsEP-dose dependent. ROS from both mitochondria and cytoplasm were upregulated with individual treatments compared to the control. Importantly, the combination treatment induced the highest level of ROS increase, indicating that ROS may participate in the cell death mechanism. Ongoing studies include the analysis of cell death pathways by Western Blot and proteomics to further identify specific death pathway(s) involved and its correlation with ROS. Our next step is to develop a prototype nsEP and NTP dual delivery system to effectively treat large pancreatic cancer in animal models and investigate if immune outcomes can be resulted from this combination therapy