Non-thermal atmospheric pressure plasma induces apoptosis in oral cavity squamous cell carcinoma: Involvement of DNA-damage-triggering sub-G1 arrest via the ATM/p53 pathway

•NTP induced apoptosis and DNA damage in oral cavity squamous cancer cells (OSCCs).•NTP induced a sub-G1 cell cycle arrest in wild-type p53 OSCCs but not in mutated p53 cells.•The ATM/p53 signaling pathway plays a significant role in NTP-induced apoptosis and sub-G1 arrest in OSCC with wild-type p53. Recent advances in physics have made possible the use of non-thermal atmospheric pressure plasma (NTP) in cancer research. Although increasing evidence suggests that NTP induces death of various cancer cell types, thus offering a promising alternative treatment, the mechanism of its therapeutic effect is little understood. In this study, we report for the first time that NTP led to apoptotic cell death in oral cavity squamous cell carcinoma (OSCC). Interestingly, NTP induced a sub-G1 arrest in p53 wild-type OSCCs, but not in p53-mutated OSCCs. In addition, NTP increased the expression levels of ATM, p53 (Ser 15, 20 and 46), p21, and cyclin D1. A comet assay, Western blotting and immunocytochemistry of γH2AX suggested that NTP-induced apoptosis and sub-G1 arrest were associated with DNA damage and the ATM/p53 signaling pathway in SCC25 cells. Moreover, ATM knockdown using siRNA attenuated the effect of NTP on cell death, sub-G1 arrest and related signals. Taken together, these results indicate that NTP induced apoptotic cell death in p53 wild-type OSCCs through a novel mechanism involving DNA damage and triggering of sub-G1 arrest via the ATM/p53 pathway. These findings show the therapeutic potential of NTP in OSCC.