title: Intense picosecond pulsed electric fields inhibit proliferation and induce apoptosis of HeLa cells.
abstract: A picosecond pulsed electric field (psPEF) is a localized physical therapy for tumors that has been developed in recent years, and that may in the future be utilized as a targeted non‑invasive treatment. However, there are limited studies regarding the biological effects of psPEF on cells. Electric field amplitude and pulse number are the main parameters of psPEF that influence its biological effects. In this study, we exposed HeLa cells to a psPEF with a variety of electric field amplitudes, from 100 to 600 kV/cm, and various pulse numbers, from 1,000 to 3,000. An MTT assay was used to detect the growth inhibition, while flow cytometry was used to determine the occurrence of apoptosis and the cell cycle of the HeLa cells following treatment. The morphological changes during cell apoptosis were observed using transmission electron microscopy (TEM). The results demonstrated that the cell growth inhibition rate gradually increased, in correlation with the increasing electric field amplitude and pulse number, and achieved a plateau of maximum cell inhibition 12 h following the pulses. In addition, typical characteristics of HeLa cell apoptosis in the experimental groups were observed by TEM. The results demonstrated that the rate of apoptosis in the experimental groups was significantly elevated in comparison with the untreated group. In the treatment groups, the rate of apoptosis was greater in the higher amplitude groups than in the lower amplitude groups. The same results were obtained when the variable was the pulse number. Flow cytometric analysis indicated that the cell cycle of the HeLa cells was arrested at the G2/M phase following psPEF treatment. Overall, our results indicated that psPEF inhibited cell proliferation and induced cell apoptosis, and that these effects occurred in a dose-dependent manner. In addition, the results demonstrated that the growth of the HeLa cells was arrested at the G2/M phase following treatment. This study may provide a foundation for further in vivo experiments, and for the potential clinical application of psPEF in the treatment of cervical cancer.
authors.affiliation: Department of Obstetrics and Gynecology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, P.R. China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Zheng-Ai
authors.initials: ZA
authors.lastname: Xiong
authors.forename: Wen-Juan
authors.initials: WJ
authors.lastname: Chen
authors.forename: Cheng-Guo
authors.initials: CG
authors.lastname: Yao
authors.forename: Zhong-Yong
authors.initials: ZY
authors.lastname: Zhao
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Hua
mesh_terms: D017209:Apoptosis; D049109:Cell Proliferation; D002470:Cell Survival; D004560:Electricity; D005434:Flow Cytometry; D059565:G2 Phase Cell Cycle Checkpoints; D006367:HeLa Cells; D006801:Humans; D059566:M Phase Cell Cycle Checkpoints; D046529:Microscopy, Electron, Transmission; D013997:Time Factors