Irreversible electroporation-mediated shRNA knockdown of the HPV18 E6 gene suppresses cervical cancer growth in vitro and in vivo.

Irreversible electroporation (IRE) is a physical, non-thermal cancer therapy, which leads to cell death via permanent membrane permeability. This differs from reversible electroporation (RE), which is used to transfer macromolecules into target cells via transient membrane permeability. Given the electrical impedance of the electric field, RE co-exists outside the central zone of IRE ablation. In the present study, the feasibility of using IRE at a therapeutic dose to mediate short hairpin RNA (shRNA) knockdown of human papillomavirus (HPV)18 E6 in HeLa cervical cancer cells in vitro and in vivo was investigated. Experimental results indicated that the HeLa cells survived the combined treatment with IRE and shRNA plasmid transfection. Additionally, residual tumor tissue in a nude mouse model demonstrated green fluorescence. Subsequent studies showed that the combined treatment inhibited the growth of HeLa cells and tumors. Western blotting analysis showed marked changes in the growth-associated proteins between the combined treatment group and the control. It was concluded that a therapeutic dose of IRE was able to mediate the transfection of HPV18 E6 shRNA into HeLa cervical cancer cells in vitro and in vivo. This combined treatment strategy has promising implications in cancer treatment for the ablation of tumors, and in eliminating microscopic residual tumor tissue.

Intense picosecond pulsed electric fields inhibit proliferation and induce apoptosis of HeLa cells.

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 non­invasive 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.

[Ca(2+) is an important mediator of nanosecond steep pulse-induced apoptosis in human ovarian cancer SKOV3 cells].

OBJECTIVE: To explore the role of Ca(2+) in nanosecond steep pulse (NSP)-induced apoptosis of human ovarian carcinoma cell line SKOV3 in vitro. METHODS: The early apoptotic rate of SKOV3 cells treated with NSP was detected by Annexin V/PI double staining and flow cytometry. MTT assay was used to detect the viability of the cells pretreated with BAPTA-AM (0, 25, 50 and 100 µmol/L) chelation for 1 h to increase the intracellular free Ca(2+) prior to NSP exposure, and the cell morphological changes and caspase 12 expression were detected using Hoechst 33342 staining and Western blotting, respectively. RESULTS: Flow cytometry showed that NSP induced early apoptosis of SKOV3 cells, and the optimal effect was achieved with the treatment parameter configuration of field strength of 90 kV/cm, pulse width of 100 ns, frequency of 1 Hz, and exposure time of 30 s. The highest early apoptotic rate and necrosis rate was (60.31∓5.67)% and (1.35∓0.39)%, respectively. Pretreatment with BAPTA-AM chelation prior to NSP exposure significantly increased the cell viability (P<0.05), and resulted also in lowered apoptosis rate and decreased expression of caspase 12 (P<0.05). CONCLUSION: NSP can induce apoptosis in SKOV3 cells. Increased intracellular free Ca(2+) functions as an important mediator in NSP-induced cell apoptosis, which may also involve Ca(2+)-mediated endo- plasmic reticulum pathway.