Purpose: To determine the effects of nonthermal plasma (NTP) induced by helium (He) alone or He plus oxygen (O₂) on the generation of reactive oxygen species (ROS) and cell death in anaplastic thyroid cancer cells.
Materials and methods: NTP was generated in He alone or He plus O₂ blowing through a nozzle by applying a high alternating current voltage to the discharge electrodes. Optical emission spectroscopy was used to identify various excited plasma species. The apoptotic effect of NTP on the anaplastic thyroid cancer cell lines, such as HTH83, U-HTH 7, and SW1763, was verified with annexin V/propidium staining and TUNEL assay. ROS formation after NTP treatment was identified with fluorescence-activated cell sorting with DCFDA staining. The mitogen-activated protein kinase pathways and caspase cascade were investigated to evaluate the molecular mechanism involved and cellular targets of plasma.
Results: NTP induced significant apoptosis in all three cancer cell lines. The plasma using He and O₂ generated more O₂-related species, and increased apoptosis and intracellular ROS formation compared with the plasma using He alone. NTP treatment of SW1763 increased the expression of phosphor-JNK, phosphor-p38, and caspase-3, but not phosphor-ERK. Apoptosis of SW1763 as well as expressions of elevated phosphor-JNK, phosphor-p38, and caspase-3 induced by NTP were effectively inhibited by intracellular ROS scavengers.
Conclusion: NTP using He plus O₂ induced significant apoptosis in anaplastic cancer cell lines through intracellular ROS formation. This may represent a new promising treatment modality for this highly lethal disease.
Keywords: Nonthermal plasma; ROS; anaplastic thyroid cancer; apoptosis; helium; oxygen.