Comparative study of nanosecond electric fields in vitro and in vivo on hepatocellular carcinoma indicate macrophage infiltration contribute to tumor ablation in vivo

Direct-Current Electrical Field Stimulation of Patient-Derived Colorectal Cancer Cells

Several cues for a directional migration of colorectal cancer cells were identified as being crucial in tumor progression. However, galvanotaxis, the directional migration in direct-current electrical fields, has not been investigated so far. Therefore, we asked whether direct-current electrical fields could be used to mobilize colorectal cancer cells along field vectors. For this purpose, five patient-derived low-passage cell lines were exposed to field strengths of 150-250 V/m in vitro, and migration along the field vectors was investigated. To further study the role of voltage-gated calcium channels on galvanotaxis and intracellular signaling pathways that are associated with migration of colorectal cancer cells, the cultures were exposed to selective inhibitors. In three out of five colorectal cancer cell lines, we found a preferred cathodal migration. The cellular integrity of the cells was not impaired by exposure of the cells to the selected field strengths. Galvanotaxis was sensitive to inhibition of voltage-gated calcium channels. Furthermore, signaling pathways such as AKT and MEK, but not STAT3, were also found to contribute to galvanotaxis in our in vitro model system. Overall, we identify electrical fields as an important contributor to the directional migration of colorectal cancer cells.

Nanosecond pulsed electric field ablates rabbit VX2 liver tumors in a non-thermal manner

BACKGROUND

Liver tumor remains an important cause of cancer-related death. Nanosecond pulsed electric fields (nsPEFs) are advantageous in the treatment of melanoma and pancreatic cancer, but their therapeutic application on liver tumors need to be further studied.

METHODS

Hep3B cells were treated with nsPEFs. The biological behaviors of cells were detected by Cell Counting Kit-8, 5-ethynyl-20-deoxyuridine, and transmission electron microscopy (TEM) assays. In vivo, rabbit VX2 liver tumor models were ablated by ultrasound-guided nsPEFs and radiofrequency ablation (RFA). Contrast-enhanced ultrasound (CEUS) was used to evaluate the ablation effect. HE staining and Masson staining were used to evaluate the tissue morphology after ablation. Immunohistochemistry was performed to determine the expression of Ki67, proliferating cell nuclear antigen, and α-smooth muscle actin at different time points after ablation.

RESULTS

The cell viability of Hep3B cells was continuously lower than that of the control group within 3 days after pulse treatment. The proliferation of Hep3B cells was significantly affected by nsPEFs. TEM showed that Hep3B cells underwent significant morphological changes after pulse treatment. In vivo, CEUS imaging showed that nsPEFs could completely ablate model rabbit VX2 liver tumors. After nsPEFs ablation, the area of tumor fibrosis and the expression of Ki67, proliferating cell nuclear antigen, and α-smooth muscle actin were decreased. However, after RFA, rabbit VX2 liver tumor tissue showed complete necrosis, but the expression of PCNA and α-smooth muscle actin did not decrease compared to the tumor group.

CONCLUSIONS

nsPEFs can induce Hep3B cells apoptosis and ablate rabbit VX2 liver tumors in a non-thermal manner versus RFA. The ultrasound contrast agent can monitor immediate effect of nsPEF ablation. This study provides a basis for the clinical study of nsPEFs ablation of liver cancer.

High-Frequency Nanosecond Bleomycin Electrochemotherapy and its Effects on Changes in the Immune System and Survival

In this work, a time-dependent and time-independent study on bleomycin-based high-frequency nsECT (3.5 kV/cm × 200 pulses) for the elimination of LLC1 tumours in C57BL/6J mice is performed. We show the efficiency of nsECT (200 ns and 700 ns delivered at 1 kHz and 1 MHz) for the elimination of tumours in mice and increase of their survival. The dynamics of the immunomodulatory effects were observed after electrochemotherapy by investigating immune cell populations and antitumour antibodies at different timepoints after the treatment. ECT treatment resulted in an increased percentage of CD4⁺ T, splenic memory B and tumour-associated dendritic cell subsets. Moreover, increased levels of antitumour IgG antibodies after ECT treatment were detected. Based on the time-dependent study results, nsECT treatment upregulated PD 1 expression on splenic CD4⁺ Tr1 cells, increased the expansion of splenic CD8⁺ T, CD4⁺CD8⁺ T, plasma cells and the proportion of tumour-associated pro inflammatory macrophages. The Lin^- population of immune cells that was increased in the spleens and tumour after nsECT was identified. It was shown that nsECT prolonged survival of the treated mice and induced significant changes in the immune system, which shows a promising alliance of nanosecond electrochemotherapy and immunotherapy.

The distinguishing electrical properties of cancer cells

In recent decades, medical research has been primarily focused on the inherited aspect of cancers, despite the reality that only 5-10% of tumours discovered are derived from genetic causes. Cancer is a broad term, and therefore it is inaccurate to address it as a purely genetic disease. Understanding cancer cells' behaviour is the first step in countering them. Behind the scenes, there is a complicated network of environmental factors, DNA errors, metabolic shifts, and electrostatic alterations that build over time and lead to the illness's development. This latter aspect has been analyzed in previous studies, but how the different electrical changes integrate and affect each other is rarely examined. Every cell in the human body possesses electrical properties that are essential for proper behaviour both within and outside of the cell itself. It is not yet clear whether these changes correlate with cell mutation in cancer cells, or only with their subsequent development. Either way, these aspects merit further investigation, especially with regards to their causes and consequences. Trying to block changes at various levels of occurrence or assisting in their prevention could be the key to stopping cells from becoming cancerous. Therefore, a comprehensive understanding of the current knowledge regarding the electrical landscape of cells is much needed. We review four essential electrical characteristics of cells, providing a deep understanding of the electrostatic changes in cancer cells compared to their normal counterparts. In particular, we provide an overview of intracellular and extracellular pH modifications, differences in ionic concentrations in the cytoplasm, transmembrane potential variations, and changes within mitochondria. New therapies targeting or exploiting the electrical properties of cells are developed and tested every year, such as pH-dependent carriers and tumour-treating fields. A brief section regarding the state-of-the-art of these therapies can be found at the end of this review. Finally, we highlight how these alterations integrate and potentially yield indications of cells' malignancy or metastatic index.

Bioelectric Potential in Next-Generation Organoids: Electrical Stimulation to Enhance 3D Structures of the Central Nervous System

Pluripotent stem cell-derived organoid models of the central nervous system represent one of the most exciting areas in in vitro tissue engineering. Classically, organoids of the brain, retina and spinal cord have been generated via recapitulation of in vivo developmental cues, including biochemical and biomechanical. However, a lesser studied cue, bioelectricity, has been shown to regulate central nervous system development and function. In particular, electrical stimulation of neural cells has generated some important phenotypes relating to development and differentiation. Emerging techniques in bioengineering and biomaterials utilise electrical stimulation using conductive polymers. However, state-of-the-art pluripotent stem cell technology has not yet merged with this exciting area of bioelectricity. Here, we discuss recent findings in the field of bioelectricity relating to the central nervous system, possible mechanisms, and how electrical stimulation may be utilised as a novel technique to engineer “next-generation” organoids.

Silver nanowire loaded poly(ε-caprolactone) nanocomposite fibers as electroactive scaffolds for skeletal muscle regeneration

Volumetric muscle loss (VML) due to trauma and tumor removal operations affects millions of people every year. Although skeletal muscle has a natural repair mechanism, it cannot provide self-healing above a critical level of VML. In this study, nanocomposite aligned fiber scaffolds as support materials were developed for volumetric skeletal muscle regeneration. For this purpose, silver nanowire (Ag NW) loaded poly(ε-caprolactone) (PCL) nanocomposite fiber scaffolds (PCL-Ag NW) were prepared to mimic the aligned electroactive structure of skeletal muscle and provide topographic and conductive environment to modulate cellular behavior and orientation. A computer-aided rotational wet spinning (RWS) system was designed to produce high-yield fiber scaffolds. Nanocomposite fiber bundles with lengths of 50 cm were fabricated via this computer-aided RWS system. The morphological, chemical, thermal properties and biodegradation profiles of PCL and PCL-Ag NW nanocomposite fibers were characterized in detail. The proliferation behavior and morphology of C2C12 mouse myoblasts were investigated on PCL and PCL-Ag NW nanocomposite fibrous scaffolds with and without electrical stimulation. Significantly enhanced cell proliferation was observed on PCL-Ag NW nanocomposite fibers compared to neat PCL fibers with electrical stimulations of 1.5 V, 3 V and without electrical stimulation.

Tumor-Associated Macrophages in Hepatocellular Carcinoma Pathogenesis, Prognosis and Therapy

Simple Summary

Hepatocellular carcinoma (HCC) constitutes a major health burden, accounting for >80% of primary liver cancers globally. Inflammation has come into the spotlight as a hallmark of cancer, and it is evident that tumor-associated inflammation drives the involvement of monocytes in tumor growth and metastasis. Tumor-associated macrophages (TAMs) actively participate in tumor-related inflammation, representing the main type of inflammatory cells in the tumor microenvironment, setting the crosstalk between tumor and stromal cells. Infiltrating TAMs exert either anti-tumorigenic (M1) or pro-tumorigenic (M2) functions. In most solid human tumors, increased TAM infiltration has been associated with enhanced tumor growth and metastasis, while other studies showcase that under certain conditions, TAMs exhibit cytotoxic and tumoricidal activity, inhibiting the progression of cancer. In this review, we summarize the current evidence on the role of macrophages in the pathogenesis and progression of HCC and we highlight their potential utilization in HCC prognosis and therapy.

Abstract

Hepatocellular carcinoma (HCC) constitutes a major health burden globally, and it is caused by intrinsic genetic mutations acting in concert with a multitude of epigenetic and extrinsic risk factors. Cancer induces myelopoiesis in the bone marrow, as well as the mobilization of hematopoietic stem and progenitor cells, which reside in the spleen. Monocytes produced in the bone marrow and the spleen further infiltrate tumors, where they differentiate into tumor-associated macrophages (TAMs). The relationship between chronic inflammation and hepatocarcinogenesis has been thoroughly investigated over the past decade; however, several aspects of the role of TAMs in HCC development are yet to be determined. In response to certain stimuli and signaling, monocytes differentiate into macrophages with antitumor properties, which are classified as M1-like. On the other hand, under different stimuli and signaling, the polarization of macrophages shifts towards an M2-like phenotype with a tumor promoting capacity. M2-like macrophages drive tumor growth both directly and indirectly, via the suppression of cytotoxic cell populations, including CD8+ T cells and NK cells. The tumor microenvironment affects the response to immunotherapies. Therefore, an enhanced understanding of its immunobiology is essential for the development of next-generation immunotherapies. The utilization of various monocyte-centered anticancer treatment modalities has been under clinical investigation, selectively targeting and modulating the processes of monocyte recruitment, activation and migration. This review summarizes the current evidence on the role of TAMs in HCC pathogenesis and progression, as well as in their potential involvement in tumor therapy, shedding light on emerging anticancer treatment methods targeting monocytes.

Effects of Nanosecond Pulsed Electric Fields in Cell Vitality, Apoptosis, and Proliferation of TPC-1 Cells

Objective

To evaluate the effects of nanosecond pulsed electric fields (nsPEFs) with different pulse durations in cell vitality, apoptosis, and proliferation of TPC-1 cells, optimize pulse parameters and expand the application range of nsPEFs.

Methods

The pulse duration of 0, 300 ns, 500 ns, and 900 ns is generated with nsPEF generator. CCK-8 was used to investigate the effect of nsPEFs on the viability of TPC-1 cells. Flow cytometry was used to evaluate the apoptosis of TPC-1 after pulse treatment. The effect of nsPEFs on the proliferation ability of TPC-1 cells was detected by 5-ethy-nyl-2′-deoxyuridine. The morphological changes of TPC-1 cells after pulse treatment were observed by transmission electron microscopy.

Results

NsPEFs with 900 ns pulse duration can significantly affect the viability of TPC-1 cells and inhibit the proliferation ability of TPC-1 cells. In addition, nsPEFs can also induce apoptosis of TPC-1 cells.

Conclusion

NsPEFs with longer pulse duration can significantly affect the biological behavior of TPC-1 cells, such as cell viability and proliferation ability, and can also induce cell apoptosis, thereby inhibiting cell growth.

Recycled algae-based carbon materials as electroconductive 3D printed skeletal muscle tissue engineering scaffolds

Skeletal muscle is an electrically and mechanically active tissue that contains highly oriented, densely packed myofibrils. The tissue has self-regeneration capacity upon injury, which is limited in the cases of volumetric muscle loss. Several regenerative therapies have been developed in order to enhance this capacity, as well as to structurally and mechanically support the defect site during regeneration. Among them, biomimetic approaches that recapitulate the native microenvironment of the tissue in terms of parallel-aligned structure and biophysical signals were shown to be effective. In this study, we have developed 3D printed aligned and electrically active scaffolds in which the electrical conductivity was provided by carbonaceous material (CM) derived from algae-based biomass. The synthesis of this conductive and functional CM consisted of eco-friendly synthesis procedure such as pre-carbonization and multi-walled carbon nanotube (MWCNT) catalysis. CM obtained from biomass via hydrothermal carbonization (CM-03) and its ash form (CM-03K) were doped within poly(ɛ-caprolactone) (PCL) matrix and 3D printed to form scaffolds with aligned fibers for structural biomimicry. Scaffolds were seeded with C2C12 mouse myoblasts and subjected to electrical stimulation during the in vitro culture. Enhanced myotube formation was observed in electroactive groups compared to their non-conductive counterparts and it was observed that myotube formation and myotube maturity were significantly increased for CM-03 group after electrical stimulation. The results have therefore showed that the CM obtained from macroalgae biomass is a promising novel source for the production of the electrically conductive scaffolds for skeletal muscle tissue engineering.

10 ns PEFs induce a histological response linked to cell death and cytotoxic T-lymphocytes in an immunocompetent mouse model of peritoneal metastasis

PURPOSE

The application of nanosecond pulsed electric fields (nsPEFs) could be an effective therapeutic strategy for peritoneal metastasis (PM) from colorectal cancer (CRC). The aim of this study was to evaluate in vitro the sensitivity of CT-26 CRC cells to nsPEFs in combination with chemotherapeutic agents, and to observe the subsequent in vivo histologic response.

METHODS

In vitro cellular assays were performed to assess the effects of exposure to 1, 10, 100, 500 and 1000 10 ns pulses in a cuvette or bi-electrode system at 10 and 200 Hz. nsPEF treatment was applied alone or in combination with oxaliplatin and mitomycin. Cell death was detected by flow cytometry, and permeabilization and intracellular calcium levels by fluorescent confocal microscopy after treatment. A mouse model of PM was used to investigate the effects of in vivo exposure to pulses delivered using a bi-electrode system; morphological changes in mitochondria were assessed by electron microscopy. Fibrosis was measured by multiphoton microscopy, while the histological response (HR; hematoxylin-eosin-safran stain), proliferation (KI67, DAPI), and expression of immunological factors (CD3, CD4, CD8) were evaluated by classic histology.

RESULTS

10 ns PEFs exerted a dose-dependent effect on CT-26 cells in vitro and in vivo, by inducing cell death and altering mitochondrial morphology after plasma membrane permeabilization. In vivo results indicated a specific CD8+ T cell immune response, together with a strong HR according to the Peritoneal Regression Grading Score (PRGS).

CONCLUSIONS

The effects of nsPEFs on CT-26 were confirmed in a mouse model of CRC with PM.

Immune response triggered by the ablation of hepatocellular carcinoma with nanosecond pulsed electric field

Nanosecond pulsed electric field (nsPEF) is a novel, nonthermal, and minimally invasive modality that can ablate solid tumors by inducing apoptosis. Recent animal experiments show that nsPEF can induce the immunogenic cell death of hepatocellular carcinoma (HCC) and stimulate the host's immune response to kill residual tumor cells and decrease distant metastatic tumors. nsPEF-induced immunity is of great clinical importance because the nonthermal ablation may enhance the immune memory, which can prevent HCC recurrence and metastasis. This review summarized the most advanced research on the effect of nsPEF. The possible mechanisms of how locoregional nsPEF ablation enhances the systemic anticancer immune responses were illustrated. nsPEF stimulates the host immune system to boost stimulation and prevail suppression. Also, nsPEF increases the dendritic cell loading and inhibits the regulatory responses, thereby improving immune stimulation and limiting immunosuppression in HCC-bearing hosts. Therefore, nsPEF has excellent potential for HCC treatment.

Comparative Analysis of Immunoactivation by Nanosecond Pulsed Electric Fields and PD-1 Blockade in Murine Hepatocellular Carcinoma

Nanosecond pulsed electric field (NsPEF) ablation effectively eliminates early-stage hepatocellular carcinoma (HCC) by local ablation and advanced HCC by inducing a remarkable and sustained host immune response. However, this approach is not sufficient to prevent cancer progression, and complementary approaches are necessary for effective immunotherapy. In this study, we evaluated the immunoactivating effects and mechanisms of action of nsPEF ablation and PD-1 blockade on an HCC orthotopic xenograft mouse model. Briefly, 24 C57BL-6J tumor-bearing mice were randomly assigned to three groups: nsPEF ablation group, anti-PD-1 administration group, and untreated control group. Tumor-infiltrating T, B, and NK cell levels and plasma concentrations of Th1 (IL-2, IFN-γ, and TNF-α), Th2 (IL-4, IL-5, IL-6, and IL-10), Th9 (IL-9), and Th17 (IL-17A, IL-17F, IL-21, and IL-22) cytokines were evaluated. Both nsPEF ablation and anti-PD-1 treatment induced immune cell infiltration in local tumors and modulated cytokine levels in the peripheral blood, with distinct changes in the two treatment groups. Based on these findings, both nsPEF ablation and PD-1 antibody administration can trigger a local and systemic immune response in a partially complementary manner, and nsPEF ablation should be considered along with PD-1 blockade for the treatment of HCC.

Recent progress in pulsed electric field ablation for liver cancer

The number of liver cancer patients is likely to continue to increase in the coming decades due to the aging of the population and changing risk factors. Traditional treatments cannot meet the needs of all patients. New treatment methods evolved from pulsed electric field ablation are expected to lead to breakthroughs in the treatment of liver cancer. This paper reviews the safety and efficacy of irreversible electroporation in clinical studies, the methods to detect and evaluate its ablation effect, the improvements in equipment and its antitumor effect, and animal and clinical trials on electrochemotherapy. We also summarize studies on the most novel nanosecond pulsed electric field ablation techniques in vitro and in vivo. These research results are certain to promote the progress of pulsed electric field in the treatment of liver cancer.

Liquid Metal Enabled Electrobiology: A New Frontier to Tackle Disease Challenges

In this article, a new conceptual biomedical engineering strategy to tackle modern disease challenges, called liquid metal (LM) enabled electrobiology, is proposed. This generalized and simple method is based on the physiological fact that specially administrated electricity induces a series of subsequent desired biological effects, either shortly, transitionally, or permanently. Due to high compliance within biological tissues, LM would help mold a pervasive method for treating physiological or psychological diseases. As highly conductive and non-toxic multifunctional flexible materials, such LMs can generate any requested electric treating fields (ETFields), which can adapt to various sites inside the human body. The basic mechanisms of electrobiology in delivering electricity to the target tissues and then inducing expected outputs for disease treatment are interpreted. The methods for realizing soft and conformable electronics based on LM are illustrated. Furthermore, a group of typical disease challenges are observed to illustrate the basic strategies for performing LM electrobiology therapy, which include but are not limited to: tissue electronics, brain disorder, immunotherapy, neural functional recovery, muscle stimulation, skin rejuvenation, cosmetology and dieting, artificial organs, cardiac pacing, cancer therapy, etc. Some practical issues regarding electrobiology for future disease therapy are discussed. Perspectives in this direction for incubating a simple biomedical tool for health care are pointed out.

Nanosecond pulsed electric fields promoting the proliferation of porcine iliac endothelial cells: An in vitro study

Currently, nanosecond pulsed electric fields (nsPEFs) with short pulse duration and non-thermal effects have various potential applications in medicine and biology, especially in tumor ablation. Additionally, there are a few investigations on its proliferative effects in the normal cell. Clinically, proliferation of endothelial cells can perhaps accelerate the stent endothelialization and reduce the risk of acute thrombosis. To explore the feasibility using nsPEFs to induce proliferation of endothelial cells, in this study, porcine iliac endothelial (PIEC) cell line was cultured and tested by CCK-8 assay after nsPEFs treatment. The results reflected that nsPEFs with low field strength (100ns, 5 kV/cm, 10 pulses) had a significant proliferative effect with an increase in the PIEC cell growth of 16% after a 48 hour’ post-treatment. To further understand the mechanism of cell proliferation, intracellular Ca²⁺ concentration was measured through fluo-4 AM and reactive oxygen species assay was applied to estimate the level of intracellular reactive oxygen species (ROS). Finally, the total nitric oxide assay for NO production in the cultured medium was evaluated. An enhanced concentration of intracellular Ca²⁺ and ROS were observed, while the concentration of extracellular NO also increased after nsPEFs treatment. Such experimental results demonstrated that nsPEFs with appropriate pulse parameters could effectively enhance cell proliferation on PIEC cells, and the cell proliferation associated strongly with the changes of intracellular Ca²⁺ concertation, ROS and NO production induced by nsPEFs treatment. This in vitro preliminary study indicates that as a novel physical doping, the nsPEFs have potential in stimulating endothelial cells to accelerate stent endothelialization.

Hepa1-6-FLuc cell line with the stable expression of firefly luciferase retains its primary properties with promising bioluminescence imaging ability

Reliable animal models are required for the in vivo study of the molecular mechanisms and effects of chemotherapeutic drugs in hepatocarcinoma. In vivo tracing techniques based on firefly luciferase (FLuc) may optimize the non-invasive monitoring of experimental animals. The present study established a murine Hepa1-6-FLuc cell line that stably expressed a retrovirus-delivered FLuc protein gene. The cell morphology, proliferation, migration and invasion ability of Hepa1-6-FLuc cells were the same as that of the Hepa1-6 cells, and thus is suitable to replace Hepa1-6 cells in the construction of hepatocarcinoma animal models. No differences in subcutaneous tumor mass and its pathomorphology from implanted Hepa1-6-FLuc cells were observed compared with Hepa1-6 control tumors. Bioluminescence imaging indicated that the Luc signal of the Hepa1-6-FLuc cells was consistently strengthened with increases in tumor mass; however, the Luc signal of Hepa1-6-AdFLuc became weaker and eventually disappeared during tumor development. Therefore, compared with the transient expression by adenovirus, stable expression of the FLuc gene in Hepa1-6 cells may better reflect cell proliferation and survival in vivo, and provide a reliable source for the establishment of hepatocarcinoma models.

Nano-pulse stimulation (NPS) ablate tumors and inhibit lung metastasis on both canine spontaneous osteosarcoma and murine transplanted hepatocellular carcinoma with high metastatic potential

Background

Nanosecond pulsed electric field (nsPEF), which is also termed as nano-pulse stimulation (NPS), has the potential of stimulating immune responses toward cancer cells. The current study investigates its local and systemic antitumor efficacy in vivo in late stage tumors with lung metastasis.

Method

The 12 canines with spontaneous osteosarcomas and 12 nude mice transplanted with human hepatocellular carcinoma were divided randomly and were given NPS treatment, surgery or no treatment control. Nanosecond pulsed electric field was delivered with puncture electrodes at 40 kV/cm with 500 pulses at 1 Hz. The survival time, tumor volume, serum alkaline phosphatase (ALP), joint capsule damage and lung metastasis were followed up. The efficacy was compared with control.

Results

Nanosecond pulsed electric field reduced primary tumor volume and extended the survival significantly compared to the control group (P<0.05). Inhibition of serum alkaline phosphatase and lung metastasis without joint deformity or thermal damage were also observed.

Conclusion

Locally applied nanosecond pulsed electric field is a novel non-thermal ablation method. It can ablate the primary tumor and decrease lung metastasis as a palliative therapy for late stage tumor.

Activation of Anti-tumor Immune Response by Ablation of HCC with Nanosecond Pulsed Electric Field

Locoregional therapy is playing an increasingly important role in the non-surgical management of hepatocellular carcinoma (HCC). The novel technique of non-thermal electric ablation by nanosecond pulsed electric field has been recognized as a potential locoregional methodology for indicated HCC. This manuscript explores the most recent studies to indicate its unique anti-tumor immune response. The possible immune mechanism, termed as nano-pulse stimulation, was also analyzed.

Effect of Low-Field High-Frequency nsPEFs on the Biological Behaviors of Human A375 Melanoma Cells

OBJECTIVE

To evaluate the effect of low-field high-frequency nanosecond pulsed electric fields (nsPEFs) on multiple biological behaviors of human A375 melanoma cells and to optimize suitable parameters for further study and clinical use.

METHODS

An nsPEF generator was developed to generate appropriate pulses. Cell apoptosis and the cell cycle were evaluated by flow cytometry. The CCK-8 assay was performed to explore the effect of nsPEFs on the viability of A375 melanoma cells. Cell migration was assessed using a Transwell Boyden Chamber. The proliferation of A375 melanoma cells was determined by the cloning efficacy test. Furthermore, the nude mouse tumorigenicity assay was used to detect the effectiveness of nsPEFs in vivo.

RESULTS

The nsPEFs with our tested parameters failed to induce apoptosis of A375 melanoma cells, though nsPEFs with high pulse duration (500 ns) induced necrosis. However, the viability and migration of A375 melanoma cells were significantly inhibited by nsPEFs. nsPEFs also suppressed the proliferation of A375 melanoma cells by restricting cells in G0/G1 phase. Moreover, animal experiments demonstrated that nsPEFs inhibited the growth of melanoma in vivo.

CONCLUSION

Low-field high-frequency nsPEFs failed to induce apoptosis but effectively inhibited the growth of melanoma via affecting other biological behaviors of melanoma cells, such as cell viability, proliferation, and migration.

SIGNIFICANCE

This study investigated the influence of low-field high-frequency nsPEFs on melanoma through evaluating their effects on multiple biological behaviors and is helpful in the treatment of melanoma and other tumors.

Environmental temperature affects physiology and survival of nanosecond pulsed electric field-treated cells

Nanosecond pulsed electric field (nsPEF) is a novel non-thermal tumor ablation technique. However, how nsPEF affect cell physiology at different environmental temperature is still kept unknown. But this issue is of critical clinical practice relevance. This work aim to investigate how nsPEF treated cancer cells react to different environmental temperatures (0, 4, 25, and 37°C). Their cell viability, apoptosis, mitochondrial membrane potential, and reactive oxygen species (ROS) were examined. Lower temperature resulted in higher apoptosis rate, decreased mitochondria membrane potential, and increased ROS levels. Sucrose and N-acetylcysteine (NAC) pre-incubation inhibit ROS generation and increase cell survival, protecting nsPEF-treated cells from low temperature-caused cell death. This work provides an experimental basis for hypothermia and fluid transfusion during nsPEF ablation with anesthesia.

Effects of electrical stimulation on cell proliferation and apoptosis

The application of exogenous electrical stimulation (ES) to cells in order to manipulate cell apoptosis and proliferation has been widely investigated as a possible method of treatment in a number of diseases. Alteration of the transmembrane potential of cells via ES can affect various intracellular signaling pathways which are involved in the regulation of cellular function. Controversially, several types of ES have proved to be effective in both inhibiting or inducing apoptosis, as well as increasing proliferation. However, the mechanisms through which ES achieves this remain fairly unclear. The aim of this review was to comprehensively summarize current findings from in vitro and in vivo studies on the effects of different types of ES on cell apoptosis and proliferation, highlighting the possible mechanisms through which ES induced these effects and define the optimum parameters at which ES can be used. Through this we hope to provide a greater insight into how future studies can most effectively use ES at the clinical trial stage.

Reaction Chemistry Generated by Nanosecond Pulsed Dielectric Barrier Discharge Treatment is Responsible for the Tumor Eradication in the B16 Melanoma Mouse Model

Melanoma is one of the most aggressive metastatic cancers with resistance to radiation and most chemotherapy agents. This study highlights an alternative treatment for melanoma based on nanosecond pulsed dielectric barrier discharge (nsP DBD). We show that a single nsP DBD treatment, directly applied to a 5 mm orthotopic mouse melanoma tumor, completely eradicates it 66% (n = 6; p ≤ 0.05) of the time. It was determined that reactive oxygen and nitrogen species produced by nsP DBD are the main cause of tumor eradication, while nsP electric field and heat generated by the discharge are not sufficient to kill the tumor. However, we do not discount that potential synergy between each plasma generated component (temperature, electric field and reactive species) can enhance the killing efficacy.

Electric Ablation with Irreversible Electroporation (IRE) in Vital Hepatic Structures and Follow-up Investigation

Irreversible electroporation (IRE) with microsecond-pulsed electric fields (μsPEFs) can effectively ablate hepatocellular carcinomas in animal models. This preclinical study evaluates the feasibility and safety of IRE on porcine livers. Altogether, 10 pigs were included. Computed tomography (CT) was used to guide two-needle electrodes that were inserted near the hilus hepatis and gall bladder. Animals were followed-up at 2 hours and at 2, 7 and 14 days post-treatment. During and after μsPEF ablation, electrocardiographs found no cardiovascular events, and contrast CT found no portal vein thrombosis. There was necrosis in the ablation zone. Mild cystic oedema around the gall bladder was found 2 hours post-treatment. Pathological studies showed extensive cell death. There was no large vessel damage, but there was mild endothelial damage in some small vessels. Follow-up liver function tests and routine blood tests showed immediate liver function damage and recovery from the damage, which correlated to the pathological changes. These results indicate that μsPEF ablation affects liver tissue and is less effective in vessels, which enable μsPEFs to ablate central tumour lesions close to the hilus hepatis and near large vessels and bile ducts, removing some of the limitations and contraindications of conventional thermal ablation.

Nanoelectroablation of Murine Tumors Triggers a CD8-Dependent Inhibition of Secondary Tumor Growth

We have used both a rat orthotopic hepatocellular carcinoma model and a mouse allograft tumor model to study liver tumor ablation with nanosecond pulsed electric fields (nsPEF). We confirm that nsPEF treatment triggers apoptosis in rat liver tumor cells as indicated by the appearance of cleaved caspase 3 and 9 within two hours after treatment. Furthermore we provide evidence that nsPEF treatment leads to the translocation of calreticulin (CRT) to the cell surface which is considered a damage-associated molecular pattern indicative of immunogenic cell death. We provide direct evidence that nanoelectroablation triggers a CD8-dependent inhibition of secondary tumor growth by comparing the growth rate of secondary orthotopic liver tumors in nsPEF-treated rats with that in nsPEF-treated rats depleted of CD8+ cytotoxic T-cells. The growth of these secondary tumors was severely inhibited as compared to tumor growth in CD8-depleated rats, with their average size only 3% of the primary tumor size after the same one-week growth period. In contrast, when we depleted CD8+ T-cells the second tumor grew more robustly, reaching 54% of the size of the first tumor. In addition, we demonstrate with immunohistochemistry that CD8+ T-cells are highly enriched in the secondary tumors exhibiting slow growth. We also showed that vaccinating mice with nsPEF-treated isogenic tumor cells stimulates an immune response that inhibits the growth of secondary tumors in a CD8+-dependent manner. We conclude that nanoelectroablation triggers the production of CD8+ cytotoxic T-cells resulting in the inhibition of secondary tumor growth.

Nanosecond pulsed electric field inhibits proliferation and induces apoptosis in human osteosarcoma

OBJECTIVE

Recent studies suggest that nanosecond pulsed electric field (nsPEF) is a novel minimal invasive and non-thermal ablation method that can induce apoptosis in different solid tumors. But the efficacy of nsPEF on bone-related tumors or bone metastasis is kept unknown. The current study investigates antitumor effect of nsPEF on osteosarcoma MG-63 cells in vitro.

METHOD

MG-63 cells were treated with nsPEF with different electric field strengths (0, 10, 20, 30, 40, and 50 kV/cm) and different pulse numbers (0, 6, 12, 18, 24, and 30 pulses). The inhibitory effect of nsPEF on the growth of MG-63 cells was measured by Cell Counting Kit-8 (CCK-8) assay at different time points (0, 3, 12, 24, and 48 h post nsPEF treatment). The apoptosis was analyzed by Hoechst stain, in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL), and flow cytometric analysis. The expression of osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), and tumor necrosis factor α (TNF-α) was examined by reverse-transcription polymerase chain reaction (RT-PCR) and western blot.

RESULTS

The CCK-8 assay showed that nsPEF induced a distinct electric field strength- and pulse number-dependent reduction of cell proliferation. For treatment parameter optimizing, the condition 40 kV/cm and 30 pulses at 24 h post nsPEF achieved the most significant apoptotic induction rate. Hoechst, TUNEL, and flow cytometric analysis showed that the cell apoptosis was induced and cells were arrested in the G0/G1 phase. PCR and western blot analysis demonstrated that nsPEF up-regulated OPG expression had no effect on RANKL, increased OPG/RANKL ratio.

CONCLUSION

NsPEF inhibits osteosarcoma growth, induces apoptosis, and affects bone metabolism by up-regulating OPG, indicating nsPEF-induced apoptosis in osteosarcoma MG-63 cells. NsPEF has potential to treat osteosarcoma or bone metastasis. When nsPEF is applied on metastatic bone tumors, it might be beneficial by inducing osteoblastic differentiation without cancer proliferation. In the future, nsPEF might be one of the treatments of metastatic bone tumor.