Cold Atmospheric Pressure Plasma-Activated Medium Induces Selective Cell Death in Human Hepatocellular Carcinoma Cells Independently of Singlet Oxygen, Hydrogen Peroxide, Nitric Oxide and Nitrite/Nitrate.

Yan Li,Tianyu Tang,Haejune Lee,Kiwon Song

doi:10.3390/ijms22115548

Abstract

Cold atmospheric pressure plasma (CAP) and plasma-activated medium (PAM) induce cell death in diverse cancer cells and may function as powerful anti-cancer agents. The main components responsible for the selective anti-cancer effects of CAP and PAM remain elusive. CAP or PAM induces selective cell death in hepatocellular carcinoma cell lines Hep3B and Huh7 containing populations with cancer stem cell markers. Here, we investigated the major component(s) of CAP and PAM for mediating the selective anti-proliferative effect on Hep3B and Huh7 cells. The anti-proliferative effect of CAP was mediated through the medium; however, the reactive oxygen species scavenger N-acetyl cysteine did not suppress PAM-induced cell death. Neither high concentrations of nitrite or nitrite/nitrate nor a low concentration of H2O2 present in the PAM containing sodium pyruvate affected the viability of Hep3B and Huh7 cells. Inhibitors of singlet oxygen, superoxide anions, and nitric oxide retained the capacity of PAM to induce anti-cancer effects. The anti-cancer effect was largely blocked in the PAM prepared by placing an aluminum metal mesh, but not a dielectric PVC mesh, between the plasma source and the medium. Hence, singlet oxygen, hydrogen peroxide, nitric oxide, and nitrite/nitrate are not the main factors responsible for PAM-mediated selective death in Hep3B and Huh7 cells. Other factors, such as charged particles including various ions in CAP and PAM, may induce selective anti-cancer effects in certain cancer cells.

Highlights

Cold atmospheric pressure plasma (CAP) and plasma-activated medium (PAM) are considered novel anti-cancer therapies based on studies showing that CAP and PAM selectively induce apoptosis in various cancer cells [1,2,3,4,5]
We showed that CAP or PAM induced selective cell death in Hepatocellular carcinoma (HCC) cell lines Hep3B and Huh7 containing populations of cells with cancer stem cell markers [20]
We demonstrated that plasma-induced selective cell death of HCC cell lines Hep3B and Huh7 cells depends on the medium, PAM

Summary

Introduction

Cold atmospheric pressure plasma (CAP) and plasma-activated medium (PAM) are considered novel anti-cancer therapies based on studies showing that CAP and PAM selectively induce apoptosis in various cancer cells [1,2,3,4,5]. We still do not completely understand the molecular mechanism of the physiological effects of CAP and PAM, thereby delaying the development of CAP and PAM as clinical therapies. CAP contains various ions, electrons, free radicals, and neutral molecules, including reactive oxygen species (ROS) and reactive nitrogen species (RNS) [1]. It primarily generates short-lived species such as hydroxyl radicals (·OH), nitric oxide radicals (·NO), superoxide radicals (O2 − ), atomic oxygen (O), singlet oxygen (1 O2 ), and excited nitrogen (N*) [1,8].

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