Pancreatic Cancer Cells Undergo Immunogenic Cell Death upon Exposure to Gas Plasma-Oxidized Ringers Lactate

SIMPLE SUMMARY: Most cancer types of cancer can spread in the body, a process called metastasis. One particular location to which cancer cells can metastasize is the belly, also referred to as peritoneal cavity. In the peritoneal cavity, several hundred small tumors can form, making surgical removal challenging. As a complementary therapy, clinicians flush the peritoneal cavity with liquid containing chemotherapeutics. While many patients benefit from this approach, there is a lack of efficacy in some of them. To this end, we here explored the anticancer effects of a liquid enriched with free radicals as potential addition or alternative to chemotherapeutics in case of their failure. This liquid, called Ringer’s lactate, is approved as medical product and frequently employed in the clinics. We also identified a unique chemistry of components in this liquid after introduction of free radical species using a process based on gas plasma technology. ABSTRACT: Survival rates among patients with pancreatic cancer, the most lethal gastrointestinal cancer, have not improved compared to other malignancies. Early tumor dissemination and a supportive, cancer-promoting tumor microenvironment (TME) limit therapeutic options and consequently impede tumor remission, outlining an acute need for effective treatments. Gas plasma-oxidized liquid treatment showed promising preclinical results in other gastrointestinal and gynecological tumors by targeting the tumor redox state. Here, carrier solutions are enriched with reactive oxygen (ROS) and nitrogen (RNS) species that can cause oxidative distress in tumor cells, leading to a broad range of anti-tumor effects. Unfortunately, clinical relevance is often limited, as many studies have forgone the use of medical-grade solutions. This study investigated the efficacy of gas plasma-oxidized Ringer’s lactate (oxRilac), a physiological solution often used in clinical practice, on two pancreatic cancer cell lines to induce tumor toxicity and provoke immunogenicity. Tumor toxicity of the oxRilac solutions was further confirmed in three-dimensional tumor spheroids monitored over 72 h and in ovo using stereomicroscope imaging of excised GFP-expressing tumors. We demonstrated that cell death signaling was induced in a dose-dependent fashion in both cell lines and was paralleled by the increased surface expression of key markers of immunogenic cell death (ICD). Nuclear magnetic resonance (NMR) spectroscopy analysis suggested putative reaction pathways that may cause the non-ROS related effects. In summary, our study suggests gas plasma-deposited ROS in clinically relevant liquids as an additive option for treating pancreatic cancers via immune-stimulating and cytotoxic effects.