Intracellular Rons Increase Induced By Helium Plasma Triggers Apoptosis In Cancer Cells

Abstract

We describe an in-vitro study aimed at elucidating the role or Reactive Oxygen and Nitrogen Species (RONS) in promoting a selective killing of cancer cells, and the possibility of emphasizing the selectivity towards cancer cells by combining the plasma treatment with the effect of a molecule known to enhance intracellular ROS production. Lung carcinoma cell lines and cultured primary cells isolated from surgical samples of laryngeal and lung cancers as well as healthy tissue counterparts were treated with an indirect plasma source, which uses a RF voltage to ionize a helium flow mixed with ambient air in the region between two brass grids [1]. The helium enriched with active chemical species is then sent to the substrate to be treated. It has already been reported that this kind of treatment induces an increase in the level of endogenous Reactive Oxygen Species (ROS) in eukaryotic human cells [2]. In the present study, ROS generation was confirmed, but the increase was markedly higher in cancer cells than in healthy ones. The same effect was observed for intracellular nitric oxide (NO). Furthermore, incubating the cells with antimycin A (AMA), a molecule known to increase ROS production [3], the effect could be amplified, both for ROS and NO. The selective increase in endogenous RONS was associated to increased expression of hypoxia-inducible factor (HIF)-α, an oxygen-sensitive transcriptional activator, and to a higher apoptosis in cancer cells than of their healthy counterparts. Again, these effects were emphasized by incubating with AMA. Overall, these results point to confirm the important role played by RONS in plasma-based cancer treatment, and to the possible combination with chemotherapeutic drugs to better tailor the selective effect induced by the plasma treatment.