Electrosensitization Increases Antitumor Effectiveness of Nanosecond Pulsed Electric Fields In Vivo

Abstract

Nanosecond pulsed electric fields are emerging as a new modality for tissue and tumor ablation. We previously reported that cells exposed to pulsed electric fields develop hypersensitivity to subsequent pulsed electric field applications. This phenomenon, named electrosensitization, is evoked by splitting the pulsed electric field treatment in fractions (split-dose treatments) and causes in vitro a 2- to 3-fold increase in cytotoxicity. The aim of this study was to show the benefit of split-dose treatments for in vivo tumor ablation by nanosecond pulsed electric field. KLN 205 squamous carcinoma cells were embedded in an agarose gel or grown subcutaneously as tumors in mice. Nanosecond pulsed electric field ablations were produced using a 2-needle probe with a 6.5-mm interelectrode distance. In agarose gel, splitting a pulsed electric field dose of 300, 300-ns pulses (20 Hz, 4.4-6.4 kV) in 2 equal fractions increased cell death up to 3-fold compared to single-train treatments. We then compared the antitumor effectiveness of these treatments in vivo. At 24 hours after treatment, sensitizing tumors by a split-dose pulsed electric field exposure (150 + 150, 300-ns pulses, 20 Hz, 6.4 kV) caused a 4- and 2-fold tumor volume reduction as compared to sham and single-train treatments, respectively. Tumor volume reduction that exceeds 75% was 43% for split-dose–treated animals compared to only 12% for single-dose treatments. The difference between the 2 experimental groups remained statistically significant for at least 1 week after the treatment. The results show that electrosensitization occurs in vivo and can be exploited to assist in vivo cancer ablation.

Electroporation and cell killing by milli- to nanosecond pulses and avoiding neuromuscular stimulation in cancer ablation

“…1 ). Seven pulse generators were used to deliver unipolar pulses: the Model 4100 isolated high-power stimulator (A-M systems, Carlsborg, WA), the Model 6040 mainframe with a 202H 300V insert (Berkley Nucleonics Corporation, San Rafael, CA), the BTX ECM830 (Harvard Bioscience, Inc., Holliston, MA), the AVTECH AVOZ-D2-B-ODA (AVTECH Electrosystems, Ottawa, Ontario, Canada) 49 , two custom-built generators (Tangers Electronics, Norfolk 40 , and VA Vilnius Gediminas Technical University, Vilnius, Lithuania 50 ), and the EPULSUS-FPM4-7 (Energy Pulse Systems, Lisbon, Portugal). Unless specified otherwise below, we applied trains of 10, 100, or 300 pulses at 10 Hz.…”

“…In fact, neuromuscular effects can be also markedly reduced with unipolar nsPEF delivered at a low frequency 39 . Applying nsPEF at low repetition rates or splitting pulse trains into short bursts with long intervals alleviates the concerns for concurrent thermal effects and may have an additional benefit of ablation with fewer pulses, by inducing electrosensitization 40 – 42 .…”

Cellular Processes Involved in Jurkat Cells Exposed to Nanosecond Pulsed Electric Field

“…In glioma, glioma cell line U87 is very sensitive to nsPEF treatment [37]. For the squamous carcinoma, compared to the sham and single-train treatments groups, tumors being sensitized with nsPEF (150 + 150, 300 ns pulses, 6.4 kV, 20 Hz) lead to a four- and two-fold tumor volume reduction in mice, respectively, which shows that nsPEF could be developed to assist in vivo cancer treatment [38]. For lung cancer and liver cancer, nsPEF (40 kV/cm, 500 pulses at 1 Hz) suppresses lung metastasis on both murine transplanted hepatocellular tumors and canine spontaneous osteosarcoma [39].…”

The Literature Review of Electricity Effects on Cell Physiology and Related New Electrical Treatment Modalities

“…Because the malignant cells are strong galvanotactic, can remove the diseased gland by applying small dc voltages. (18,19,20) The electrical frequency of most cells in human tissues are different. For example, slow oscillations at theta frequencies (4)(5)(6)(7)(8)(9)(10)(11)(12) are consistently recorded in the hippocampus during working tasks, spatial navigation, and storage of episodic memory.…”