Activation of apoptotic cell death in human myeloid leukemia cells by RNS: A novel antitumor approach using resistive barrier plasma

Cold atmospheric plasma (CAP), an ambient temperature ionized gas, is undergoing extensive evaluation as a promising addition to anti-tumor therapy primarily due to the ability to generate and control delivery of electrons, ions, free radicals, excited atoms and molecules, UV photons, and reactive species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) to a specific site. The heterogeneous composition of CAP offers the opportunity to mediate several signaling pathways that regulate tumor cells. Consequently, the array of CAP generated products has limited the identification of the mechanisms of action on tumor cells. The aim of this work was to assess the cell death response of human myeloid leukemia cells exposed to CAP generated RNS. We evaluated the viability of the human monocytic leukemia cell line THP-1 to variable treatments of CAP generated RNS and we set to identify specific cell death characteristics that presented with increasing dosages of CAP generated RNS. Incorporation of exclusionary dyes and fluorescently labeled annexin V allowed us to determine that CAP generated RNS promotes apoptosis and/or necrosis in THP-1 cells in a dosage- and time-dependent manner. CAP generated RNS promotion of apoptosis was further supported by observation of endonuclease cleavage products by agarose gel electrophoresis. In conclusion, we identify that CAP generated RNS play a significant role in the anti-tumor potential of CAP and show a possible application of modified CAP devices in tumor therapy^{1, 2}. Recent results on RNA analysis will be presented as well.