Electrochemotherapy: from the drawing board into medical practice

Bystander effect of metal byproducts released from electroporated cells after electroporation in vitro

Electrodes dissolution during electroporation releases metal ions into the medium, altering the microenvironment of electroporated cells and allowing metal ions to penetrate cell membrane. During cell membrane repair, homeostasis restoration or activation of cell death pathways, cells eliminate excess metals from the cytoplasm and membrane. This study assessed the effects of post-electroporation metal byproducts on untreated (non-electroporated) cells in vitro. CHO and HCT116 cells were electroporated with three pulse protocols (unipolar: 100 μs, 5 ms; bipolar: 2 μs) using either aluminum or stainless-steel electrodes. After electroporation, cells were transferred to fresh growth medium and incubated for 2 or 4 h. Incubation period allowed either cell recovery or the activation of cell death pathways, leading to the accumulation of metal byproducts in the incubation medium. Stainless-steel electrodes with the 5 ms pulse protocol caused a considerable increase in iron, chromium and nickel ions in incubation medium compared to aluminum electrodes or other protocols. Metal ions in incubation medium caused toxicity in non-electroporated cells, disrupting cell cycle function or inducing cell death. The observed toxicity results from combined effects of metal ions on cellular functions and the mechanisms the cells use to protect themselves from metal overload.

Efficient gene transfer by pulse parameters for electrochemotherapy of cells in vitro and in muscle and melanoma tumors in mice

BACKGROUND

In recent years, various gene therapy strategies have been developed for cancer treatment. One of these strategies is electroporation-based delivery of therapeutic transgenes - gene electrotransfer (GET). Electrochemotherapy and GET have been combined in several contemporary preclinical and veterinary studies. In most cases, two different pulse protocols are used, each for a specific treatment. The aim of our current study was to test whether the standard pulse protocol used in daily clinical practice for electrochemotherapy can also be used for effective GET.

MATERIALS AND METHODS

Experiments were performed in vitro in a tumor (B16F10) and two normal tissue cell lines (C2C12 myoblasts and L929 fibroblasts). Four different GET protocols, three using monopolar electric pulses and one bipolar electric pulses, were tested for the GET of plasmid DNA, which codes for green fluorescent protein in vitro. In addition, two GET protocols were chosen for in vivo tumor and muscle transfection.

RESULTS

Two GET protocols using monopolar electric pulses of different voltages delivered at 1 Hz transfected B16F10 tumor cells significantly better than normal cells. GET4 protocol, which uses monopolar electric pulses at 5 kHz, again transfected the B16F10 tumor cells significantly better, but the difference to the C2C12 myoblast cells was not significant. Compared with other GET protocols, GET3 using bipolar electric pulses at 1 Hz was significantly less effective. Both the GET2 (1 Hz) and GET4 (5 kHz) protocols resulted in similar tumor transfection efficiencies, whereas only the GET4 protocol was effective for muscle transfection in vivo.

CONCLUSIONS

Our study demonstrated the efficient transfection of tumors and muscles with the GET4 pulse protocol, which is used clinically for electrochemotherapy. The use of this protocol could enable simultaneous electrochemotherapy and GET of the therapeutic gene in one session, which will significantly shorten the procedure and thus will be more tolerable for patients.

Advancing cancer therapy: Mechanisms, efficacy, and limitations of calcium electroporation

Calcium electroporation, an innovative technique, uses high-voltage pulses to introduce calcium ions into cells, leading to cell death and tumor growth inhibition. This review explores the potential of calcium electroporation as a promising therapeutic approach in cancer treatment. We provide an in-depth analysis of the underlying mechanisms by which calcium ions function within cells and how their introduction through electroporation can effectively induce cell death in cancer cells. Furthermore, we present a comprehensive overview of the current literature, covering both preclinical and clinical studies, to highlight the safety and efficacy of calcium electroporation in various cancer types, including melanoma, head and neck cancer, and breast cancer. We also discuss the distinct advantages of calcium electroporation over traditional cancer therapies, such as its specific targeting of cancer cells while sparing healthy cells. However, we also address the challenges and limitations associated with this technique, underscoring the need for further research. By providing a comprehensive examination of calcium electroporation, this review aims to contribute to understanding this emerging field and encourage further investigation into its potential as a novel cancer treatment strategy.

Reversible electroporation for cancer therapy

Reversible electroporation (EP) refers to the use of high-voltage electrical pulses on tissues to increase cell membrane permeability. It allows targeted delivery of high concentrations of chemotherapeutic agents including cisplatin and bleomycin, a process known as electrochemotherapy (ECT). It can also be used to deliver toxic concentrations of calcium and gene therapies that stimulate an anti-tumour immune response. ECT was validated for palliative treatment of cutaneous tumours. Evidence to date shows a mean objective response rate of ∼80% in these patients. Regression of non-treated lesions has also been demonstrated, theorized to be from an in situ vaccination effect. Advances in electrode development have also allowed treatment of deep-seated metastatic lesions and primary tumours, with safety demonstrated in vivo. Calcium EP and combination immunotherapy or immunogene electrotransfer is also feasible, but research is limited. Adverse events of ECT are minimal; however, general anaesthesia is often necessary, and improvements in modelling capabilities and electrode design are required to enable sufficient electrical coverage. International collaboration between preclinical researchers, oncologists, and interventionalists is required to identify the most effective combination therapies, to optimize procedural factors, and to expand use, indications and assessment of reversible EP. Registries with standardized data collection methods may facilitate this.

Potentiation of Gelonin Cytotoxicity by Pulsed Electric Fields

Gelonin is a ribosome-inactivating protein with extreme intracellular toxicity but poor permeation into cells. Targeted disruption of cell membranes to facilitate gelonin entry is explored for cancer and tissue ablation. We demonstrate a hundreds- to thousands-fold enhancement of gelonin cytotoxicity by pulsed electric fields in the T24, U-87, and CT26 cell lines. The effective gelonin concentration to kill 50% of cells (EC50) after electroporation ranged from <1 nM to about 100 nM. For intact cells, the EC50 was unattainable even at the highest gelonin concentration of 1000 nM, which reduced cell survival by only 5-15%. For isoeffective electroporation treatments using 300 ns, 9 µs, and 100 µs pulses, longer pulses were more efficient at lowering gelonin EC50. Increasing the electric field strength of 8, 100 µs pulses from 0.65 to 1.25 kV/cm reduced gelonin EC50 from 128 nM to 0.72 nM. Conversely, the presence of 100 nM gelonin enabled a more than 20-fold reduction in the number of pulses required for equivalent cell killing. Pulsed electric field-mediated delivery of gelonin shows promise for hyperplasia ablation at concentrations sufficiently low to minimize or avoid systemic toxicity.

Stereotactic Percutaneous Electrochemotherapy as a New Minimal Invasive Treatment Modality for Primary and Secondary Liver Malignancies

Background and Objectives: To report on the first results of safety, efficacy, and outcome of CT-navigated stereotactic percutaneous electrochemotherapy (SpECT) in patients with primary and secondary liver malignancies. Methods: This retrospective study included 23 consecutive lesions in 22 patients who underwent SpECT for primary and secondary malignant liver lesions with locally curative intention. The endpoints were primary technique efficacy (PTE), local tumor progression (LTP), time to progression (TTP), and occurrence of adverse events. Results: The mean maximum diameter of the treated lesions was 42 mm (range: 16 mm-72 mm). Eight lesions were hepatocellular carcinoma (34.8%), five lesions were colorectal liver metastases (21.7%), three lesions were cholangiocellular carcinoma (13.0%), and the other seven lesions were liver metastases from different primary cancers (30.4%). PTE was achieved for 22 lesions (95.7%). The mean follow-up time was 15 months (0-39 months). No LTP was observed. In six patients (27.3%), hepatic tumor progression was observed during follow-up with a mean TTP of 3.8 months (2-8 months). In 10 procedures (43.5%), minor complications (1 CIRSE Grade 2) and side effects occurred, but no major complications were observed. Conclusions: SpECT seems to be a safe and effective new local treatment modality for primary and secondary liver malignancies.

Enhancing lung cancer growth inhibition with calcium ions: Role of mid- and high-frequency electric field pulses

Calcium electroporation (CaEP) involves the combination of calcium ions with electroporation, which is induced by pulsed electric fields (PEFs). This study explores the application of high-frequency unipolar nanosecond pulsed electric fields (nsPEFs: 8-14 kV/cm, 200 ns, 10 kHz, 100 kHz, 1 MHz repetition frequency pulse bursts, n = 100) and their potential in inhibiting lung cancer cell growth. As a reference, standard microsecond range parametric protocols were used (100 µs x 8 pulses). Methods included cell permeability quantification through Yo-Pro-1 uptake, cell viability assays, immunofluorescence studies for apoptosis and EMT markers, analysis of cell death types depending on repetition frequency pulse bursts. We determined the susceptibility of human lung cancer to electric pulses, characterized the efficacy of CaEP, and investigated cell death types depending on repetition frequency pulse bursts. We have shown that adding calcium ions to the applied nsPEF protocol increases cytotoxicity. Additionally, the use of these electroporation parameters can modulate key cellular processes, such as the epithelial-mesenchymal transition and apoptosis, as indicated by changes in the expression of markers such as E-cadherin, N-cadherin, BCL-2, and p53. Changes in cell morphology over time were observed using holotomographic microscopy. The study provides insights into the modulation of key cellular processes, indicating that nsPEF technology could improve the outcomes of conventional cancer treatments through enhanced efficacy and potentially mitigating drug resistance mechanisms. The promising results advocate for further research to optimize nsPEF protocols for clinical application, highlighting the potential of electrical fields in advancing cancer therapy.

Histopathological and immunohistochemical analysis of a suspected extraskeletal osteosarcoma in a rabbit (Oryctolagus cuniculus)

An 8-year-old male rabbit (Oryctolagus cuniculus) presented with a subcutaneous mass in the proximal region of the fourth and accessory digit measuring 5.5 x 3.5 x 5.2cm. The mass was non-alopecic and exhibited irregular surface, ulceration and necrosis with predominantly pale and light brown coloring. Radiography revealed no involvement of bone and adjacent periosteum. The mass was marginally resected and the electrochemotherapy (ECT) was performed on the surgical bed. Histopathology and immunohistochemical analysis revealed positive reactions for Vimentin, Runx-2 and ki-67, leading to a diagnosis of extraskeletal osteosarcoma (ESOS). This report described a case of ESOS in a rabbit, thereby delineating its clinical presentation, anatomopathological characteristics, diagnostic modalities and recommended therapeutic interventions.

Application of Gold Nanoparticles for Improvement of Electroporation-Assisted Drug Delivery and Bleomycin Electrochemotherapy

Background/Objectives: Electrochemotherapy (ECT) is a safe and efficient method of targeted drug delivery using pulsed electric fields (PEF), one that is based on the phenomenon of electroporation. However, the problems of electric field homogeneity within a tumor can cause a diminishing of the treatment efficacy, resulting only in partial response to the procedure. This work used gold nano-particles for electric field amplification, introducing the capability to improve available elec-trochemotherapy methods and solve problems associated with field non-homogeneity. Methods: We characterized the potential use of gold nanoparticles of 13 nm diameter (AuNPs: 13 nm) in combination with microsecond (0.6-1.5 kV/cm × 100 μs × 8 (1 Hz)) and nanosecond (6 kV/cm × 300-700 ns × 100 (1, 10, 100 kHz and 1 MHz)) electric field pulses. Finally, we tested the most prominent protocols (microsecond and nanosecond) in the context of bleomycin-based electrochemotherapy (4T1 mammary cancer cell line). Results: In the nano-pulse range, the synergistic effects (improved permeabilization and electrotransfer) were profound, with increased pulse burst frequency. Addi-tionally, AuNPs not only reduced the permeabilization thresholds but also affected pore resealing. It was shown that a saturated cytotoxic response with AuNPs can be triggered at significantly lower electric fields and that the AuNPs themselves are non-toxic for the cells either separately or in combination with bleomycin. Conclusions: The used electric fields are considered sub-threshold and/or not applicable for electrochemotherapy, however, when combined with AuNPs results in successful ECT, indicating the methodology's prospective applicability as an anticancer treatment method.

Comparison of Three Chemotherapy Protocols With Electrochemotherapy for the Treatment of Feline Cutaneous Squamous Cell Carcinoma

Electrochemotherapy (ECT) with intravenous (IV) and/or intratumoral (IT) bleomycin has shown considerable efficacy in the treatment of non-resectable feline cutaneous squamous cell carcinoma (cSCC), boasting response rates of up to 95%, but other chemotherapy protocols have not yet been investigated. The objective of this prospective multicentre study was to compare the overall response rate (ORR) and progression-free interval (PFI) between cats with cSCC treated with ECT using IT and IV carboplatin (IV + IT), IV carboplatin (IV) or IV bleomycin (IV). A total of 44 cats with unresectable cSCC across three centres were enrolled and treated with ECT using carboplatin IV + IT (n = 10), carboplatin IV (n = 11) or bleomycin IV (n = 23). Treatment response according to RECIST criteria was recorded at 2 and 4 weeks post-treatment, and patients were followed until disease progression and/or death. All three groups were comparable regarding age, sex, weight, and lesion size. Adverse events were generally mild, localised and similar between groups. ORRs were 90.0% (carboplatin IV + IT), 90.9% (carboplatin IV) and 95.6% (bleomycin IV) and were not significantly different (p = 0.79). Median PFI was not reached for carboplatin IV + IT or carboplatin IV and was 566 days for bleomycin IV, with no significant difference between the three groups (p = 0.81). This study suggests that ECT using IV or IV + IT carboplatin is a reasonable alternative therapeutic option for managing cSCC, and further studies are warranted to compare outcomes between treatment protocols.

Accelerated Bone Healing via Electrical Stimulation

Piezoelectric effect produces an electrical signal when stress is applied to the bone. When the integrity of the bone is destroyed, the biopotential within the defect site is reduced and several physiological responses are initiated to facilitate healing. During the healing of the bone defect, the bioelectric potential returns to normal levels. Treatment of fractures that exceed innate regenerative capacity or exhibit delayed healing requires surgical intervention for bone reconstruction. For bone defects that cannot heal on their own, exogenous electric fields are used to assist in treatment. This paper reviews the effects of exogenous electrical stimulation on bone healing, including osteogenesis, angiogenesis, reduction in inflammation and effects on the peripheral nervous system. This paper also reviews novel electrical stimulation methods, such as small power supplies and nanogenerators, that have emerged in recent years. Finally, the challenges and future trends of using electrical stimulation therapy for accelerating bone healing are discussed.

Preclinical evaluation of reversible pulsed electrical field: electrophysiological and histological assessment of myocardium

Background

Pulsed field ablation, as a non-thermal ablation modality, has received increasing attention. The aim of this study is to explore whether a reversible pulsed electric field (RPEF) can temporarily inhibit electrical conduction and provide a novel method for precise ablation of arrhythmia.

Methods

RPEF energy was delivered from an ablation catheter to the atrium of six dogs, followed by a series of electrogram and histology assessments.

Results

RPEF ablation of ordinary myocardium resulted in an average reduction of 68.3% (range, 53.7%-83.8%) in electrogram amplitude, while 5 min later, the amplitude in eight electrograms returned to 77.9% (range, 72.4%-87.3%) of baseline. Similarly, the amplitude of the sinoatrial node electrograms reduced by an average of 73.0% (range, 60.2%-84.4%) after RPEF ablation, but recovered to 84.9% (range, 80.3%-88.5%) of baseline by 5 min. No necrotic change was detected in histopathology. Transient third-degree atrioventricular block occurred following the ablation of the maximum His potential sites with RPEF, the duration of which was voltage dependent. The histopathological results showed necrosis of the myocardium at the ablation sites but no injury to His bundle cells.

Conclusions

RPEF can be applied to transiently block electrical conduction in myocardial tissues contributing to precise ablation.

Gene Electrotransfer via Conductivity-Clamped Electric Field Focusing Pivots Sensori-Motor DNA Therapeutics: "A Spoonful of Sugar Helps the Medicine Go Down"

Viral vectors and lipofection-based gene therapies have dispersion-dependent transduction/transfection profiles that thwart precise targeting. The study describes the development of focused close-field gene electrotransfer (GET) technology, refining spatial control of gene expression. Integration of fluidics for precise delivery of "naked" plasmid deoxyribonucleic acid (DNA) in sucrose carrier within the focused electric field enables negative biasing of near-field conductivity ("conductivity-clamping"-CC), increasing the efficiency of plasma membrane molecular translocation. This enables titratable gene delivery with unprecedently low charge transfer. The clinic-ready bionics-derived CC-GET device achieved neurotrophin-encoding miniplasmid DNA delivery to the cochlea to promote auditory nerve regeneration; validated in deafened guinea pig and cat models, leading to improved central auditory tuning with bionics-based hearing. The performance of CC-GET is evaluated in the brain, an organ problematic for pulsed electric field-based plasmid DNA delivery, due to high required currents causing Joule-heating and damaging electroporation. Here CC-GET enables safe precision targeting of gene expression. In the guinea pig, reporter expression is enabled in physiologically critical brainstem regions, and in the striatum (globus pallidus region) delivery of a red-shifted channelrhodopsin and a genetically-encoded Ca2+ sensor, achieved photoactivated neuromodulation relevant to the treatment of Parkinson's Disease and other focal brain disorders.

Electrochemotherapy with intravenous, intratumoral, or combined administration of bleomycin in the treatment of colorectal hepatic metastases in a rat model

Electrochemotherapy (ECT) combines the reversible electroporation (rEP) with intravenous (i.v.) or intratumoral (i.t.) administration of chemotherapeutic drugs. We conducted this study to compare the efficacy of i.v., i.t., and i.v. + i.t. injection of bleomycin (BLM) in ECT treatment of colorectal hepatic metastases in a rat model. WAG/Rij rats were randomized into three groups and underwent ECT with i.v., i.t., or i.v. + i.t. injection of BLM. Tumor volumes and oxygenation were measured by means of ultrasound and photoacoustic imaging. Moreover, liver and tumor tissue were analyzed by histology and immunohistochemistry. The i.v. and i.v. + i.t. groups exhibited a 44.0% and 46.6% reduction in oxygen saturation of the tumor tissue when compared to pretreatment values, whereas the i.t. group only showed a reduction of 35.2%. The extent of tumor tissue necrosis did not statistically differ between the groups. However, the i.t. group showed a tendency towards a lower necrosis rate. Cell proliferation, apoptotic cell death, vascularization, and immune cell infiltration were comparable in the treated tumors of the three groups. ECT with i.v. administration of BLM should be preferred in clinical practice, as the combined i.v. + i.t. therapy did not show superior oncological outcomes in the present study.

Electroporation with Calcium or Bleomycin: First Application in an In Vivo Uveal Melanoma Patient-Derived Xenograft Model

Uveal melanoma (UM) represents a rare tumor of the uveal tract and is associated with a poor prognosis due to the high risk of metastasis. Despite advances in the treatment of UM, the mortality rate remains high, dictating an urgent need for novel therapeutic strategies. The current study introduces the first in vivo analysis of the therapeutic potential of calcium electroporation (CaEP) compared with electrochemotherapy (ECT) with bleomycin in a patient-derived xenograft (PDX) model based on the chorioallantoic membrane (CAM) assay. The experiments were conducted as monotherapy with either 5 or 10 mM calcium chloride or 1 or 2.5 µg/mL bleomycin in combination with EP or EP alone. CaEP and ECT induced a similar reduction in proliferative activity, neovascularization, and melanocytic expansion. A dose-dependent effect of CaEP triggered a significant induction of necrosis, whereas ECT application of 1 µg/mL bleomycin resulted in a significantly increased apoptotic response compared with untreated tumor grafts. Our results outline the prospective use of CaEP and ECT with bleomycin as an adjuvant treatment of UM, facilitating adequate local tumor control and potentially an improvement in metastatic and overall survival rates.

Considering Joule heating in coupled electroporation and electrodeformation modeling of glioblastoma cells

Cells exposed to a pulsed electric field undergo electroporation(EP) and electrodeformation(ED) under electric field stress, and a coupled model of EP and ED of glioblastoma(GBM) taking into account Joule heating is proposed. The model geometry is extracted from real cell boundaries, and the effects of Joule heating-induced temperature rise on the EP and ED processes are considered. The results show that the temperature rise will increase the cell's local conductivity, leading to a decrease in the transmembrane potential(TMP). The temperature rise also causes a decrease in the dynamic Young's modulus of the cell membrane, making the cell less resistant to deformation. In addition, GBM cells are more susceptible to EP in the middle portion of the cell and ED in the three tentacle portions under pulsed electric fields, and the cells undergo significant positional shifts. The ED of the nucleus is similar to spherical cells, but the degree of ED is smaller.

Tolerability of a piezoelectric microneedle electroporator in human subjects

Electroporation, or the use of electric pulses to facilitate the intracellular delivery of DNA, RNA, and other molecules, is a well-established technique, that has been demonstrated to significantly augment the immunogenicity of DNA/mRNA vaccines and therapeutics. However, the clinical translation of traditional electroporators has been limited due to high costs, large size, complex user operation, and poor tolerability in humans due to nerve stimulation. In prior work, we introduced ePatch: an ultra-low-cost, handheld, battery-free electroporator employing a piezoelectric pulser coupled with a microneedle electrode array that showed enhanced immunogenic responses to an intradermal SARS-CoV-2 DNA vaccine in mice. The current study shifts focus from efficacy to tolerability, hypothesizing that ePatch's microneedle array, which localizes the electric field to the superficial skin strata, will minimize nerve stimulation and improve patient comfort. We tested this hypothesis in 14 healthy adults, monitoring pain and other potential adverse effects associated with electroporation. Compared to the insertion of a traditional hypodermic needle, the ePatch was less painful. Adverse effects such as pain, tenderness, erythema and swelling at the application sites were minimal, transient, and statistically indistinguishable between the experimental and placebo ePatch application, suggesting excellent tolerability towards electroporation. In summary, ePatch has a favorable tolerability profile in humans and offers the potential for the safe use of electroporation in a variety of clinical settings, including DNA and mRNA vaccination.

Review of Role of Surgery with Electroporation in Melanoma: Chemotherapy, Immunotherapy, and Gene Delivery

Electroporation with chemotherapy (ECT) is currently offered as a treatment in Europe for locoregional or metastatic melanoma with cutaneous lesions. However, the role of surgery and other forms of electroporation in melanoma requires further evaluation. Two reviewers used two databases to conduct a literature search and review, and 51 publications related to electroporation with chemotherapy, immunotherapy, or gene delivery were found. ECT appears to be effective in reducing tumor burden for surgical resection, replacing surgical intervention with evidence of complete regression in some lesions, and inducing both local and systemic immune effects. These immune effects are pronounced when ECT is combined with immunotherapy, with a statistically significant improvement in overall survival (OS). Other forms of electroporation, such as those using calcium chloride, an IL-12 plasmid, and vaccination, require further study. However, IL-12 plasmid electroporation may be inferior to ECT based on the evidence available. Furthermore, irradiation of the tumor prior to ECT treatment is negatively correlated with local response. Access to ECT is restricted in the US and requires further evaluation. More randomized controlled trials of ECT and electroporation treatment in locoregional melanoma are recommended.

The Efficacy of Electrochemotherapy with Dacarbazine on Melanoma Cells

Electrochemotherapy (ECT) involves locally applying electrical pulses to permeabilize cell membranes, using electroporation (EP). This process enhances the uptake of low-permeant chemotherapeutic agents, consequently amplifying their cytotoxic effects. In melanoma treatment, dacarbazine (DTIC) is a cornerstone, but it faces limitations because of poor cell membrane penetration, necessitating the use of high doses, which, in turn, leads to increased side effects. In our study, we investigated the effects of DTIC and EP, both individually and in combination, on the melanoma cell line (SK-MEL-30) as well as human dermal fibroblasts (HDF) using in vitro assays. First, the effects of different DTIC concentrations on the viability of SK-MEL-30 and HDF cells were determined, revealing that DTIC was more effective against melanoma cells at lower concentrations, whereas its cytotoxicity at 1000 μM was similar in both cell types. Next, an ideal electric field strength of 1500 V/cm achieved a balance between permeability (84%) and melanoma cell viability (79%), paving the way for effective ECT. The combined DTIC-EP (ECT) application reduced IC50 values by 2.2-fold in SK-MEL-30 cells and 2.7-fold in HDF cells compared with DTIC alone. In conclusion, ECT not only increased DTIC's cytotoxicity against melanoma cells but also affected healthy fibroblasts. These findings emphasize the need for cautious, targeted ECT management in melanoma therapy.

The equivalence of different types of electric pulses for electrochemotherapy with cisplatin - an in vitro study

BACKGROUND

Electrochemotherapy (ECT) is a treatment involving the administration of chemotherapeutics drugs followed by the application of 8 square monopolar pulses of 100 μs duration at a repetition frequency of 1 Hz or 5000 Hz. However, there is increasing interest in using alternative types of pulses for ECT. The use of high-frequency short bipolar pulses has been shown to mitigate pain and muscle contractions. Conversely, the use of millisecond pulses is interesting when combining ECT with gene electrotransfer for the uptake of DNA-encoding proteins that stimulate the immune response with the aim of converting ECT from a local to systemic treatment. Therefore, the aim of this study was to investigate how alternative types of pulses affect the efficiency of the ECT.

MATERIALS AND METHODS

We performed in vitro experiments, exposing Chinese hamster ovary (CHO) cells to conventional ECT pulses, high-frequency bipolar pulses, and millisecond pulses in the presence of different concentrations of cisplatin. We determined cisplatin uptake by inductively coupled plasma mass spectrometry and cisplatin cytotoxicity by the clonogenic assay.

RESULTS

We observed that the three tested types of pulses potentiate the uptake and cytotoxicity of cisplatin in an equivalent manner, provided that the electric field is properly adjusted for each pulse type. Furthermore, we quantified that the number of cisplatin molecules, resulting in the eradication of most cells, was 2-7 × 107 per cell.

CONCLUSIONS

High-frequency bipolar pulses and millisecond pulses can potentially be used in ECT to reduce pain and muscle contraction and increase the effect of the immune response in combination with gene electrotransfer, respectively.

Electrochemotherapy for head and neck cancers: possibilities and limitations

Head and neck cancer continues to be among the most prevalent types of cancer globally, yet it can be managed with appropriate treatment approaches. Presently, chemotherapy and radiotherapy stand as the primary treatment modalities for various groups and regions affected by head and neck cancer. Nonetheless, these treatments are linked to adverse side effects in patients. Moreover, due to tumor resistance to multiple drugs (both intrinsic and extrinsic) and radiotherapy, along with numerous other factors, recurrences or metastases often occur. Electrochemotherapy (ECT) emerges as a clinically proven alternative that offers high efficacy, localized effect, and diminished negative factors. Electrochemotherapy involves the treatment of solid tumors by combining a non-permeable cytotoxic drug, such as bleomycin, with a locally administered pulsed electric field (PEF). It is crucial to employ this method effectively by utilizing optimal PEF protocols and drugs at concentrations that do not possess inherent cytotoxic properties. This review emphasizes an examination of diverse clinical practices of ECT concerning head and neck cancer. It specifically delves into the treatment procedure, the choice of anti-cancer drugs, pre-treatment planning, PEF protocols, and electroporation electrodes as well as the efficacy of tumor response to the treatment and encountered obstacles. We have also highlighted the significance of assessing the spatial electric field distribution in both tumor and adjacent tissues prior to treatment as it plays a pivotal role in determining treatment success. Finally, we compare the ECT methodology to conventional treatments to highlight the potential for improvement and to facilitate popularization of the technique in the area of head and neck cancers where it is not widespread yet while it is not the case with other cancer types.

Electrochemotherapy combined with immunotherapy - a promising potential in the treatment of cancer

Electrochemotherapy is a novel, locoregional therapy that is used to treat cutaneous and deep-seated tumors. The electric pulses used in electrochemotherapy increase the permeability of the cell membranes of the target lesion and thus enhance the delivery of low-permeant cytotoxic drugs to the cells, leading to their death. It has also been postulated that electrochemotherapy acts as an in situ vaccination by inducing immunogenic cell death. This in turn leads to an enhanced systemic antitumor response, which could be further exploited by immunotherapy. However, only a few clinical studies have investigated the role of combined treatment in patients with melanoma, breast cancer, hepatocellular carcinoma, and cutaneous squamous cell carcinoma. In this review, we therefore aim to review the published preclinical evidence on combined treatment and to review clinical studies that have investigated the combined role of electrochemotherapy and immunotherapy.

Dynamics of Cell Death Due to Electroporation Using Different Pulse Parameters as Revealed by Different Viability Assays

The mechanisms of cell death due to electroporation are still not well understood. Recent studies suggest that cell death due to electroporation is not an immediate all-or-nothing response but rather a dynamic process that occurs over a prolonged period of time. To investigate whether the dynamics of cell death depends on the pulse parameters or cell lines, we exposed different cell lines to different pulses [monopolar millisecond, microsecond, nanosecond, and high-frequency bipolar (HFIRE)] and then assessed viability at different times using different viability assays. The dynamics of cell death was observed by changes in metabolic activity and membrane integrity. In addition, regardless of pulse or cell line, the dynamics of cell death was observed only at high electroporation intensities, i.e., high pulse amplitudes and/or pulse number. Considering the dynamics of cell death, the clonogenic assay should remain the preferred viability assay for assessing viability after electroporation.

Histologic changes of porcine portal vein anastomosis after electrochemotherapy with bleomycin

Electrochemotherapy (ECT1) is used for treatment of unresectable abdominal malignancies. This study aims to show that ECT of porcine portal vein anastomosis is safe and feasible in order to extend the indications for margin attenuation after resection of locally advanced pancreatic carcinoma. No marked differences were found between the control group and ECT treated groups. Electroporation thus caused irreversible damage to the vascular smooth muscle cells in tunica media that could bedue to the narrow irreversible electroporation zone that may occur near the electrodes, or due to vasa vasorum thrombosis in the tunica externa. Based on the absence of vascular complications, and similar histological changes in lienal veinanastomosis, we can conclude that ECT of portal vein anastomosis is safe and feasible.

Research frontiers of electroporation-based applications in cancer treatment: a bibliometric analysis

OBJECTIVES

Electroporation, the breakdown of the biomembrane induced by external electric fields, has increasingly become a research hotspot for its promising related methods in various kinds of cancers.

CONTENT

In this article, we utilized CiteSpace 6.1.R2 to perform a bibliometric analysis on the research foundation and frontier of electroporation-based applications in cancer therapy. A total of 3,966 bibliographic records were retrieved from the Web of Science Core Collection for the bibliometric analysis. Sersa G. and Mir L. M. are the most indispensable researchers in this field, and the University of Ljubljana of Slovenia is a prominent institution. By analyzing references and keywords, we found that, with a lower recurrence rate, fewer severe adverse events, and a higher success rate, irreversible electroporation, gene electrotransfer, and electrochemotherapy are the three main research directions that may influence the future treatment protocol of cancers.

SUMMARY

This article visualized relevant data to synthesize scientific research on electroporation-based cancer therapy, providing helpful suggestions for further investigations on electroporation.

OUTLOOK

Although electroporation-based technologies have been proven as promising tools for cancer treatment, its radical mechanism is still opaque and their commercialization and universalization need further efforts from peers.

Electroacoustic tomography for real-time visualization of electrical field dynamics in deep tissue during electroporation

Despite the widespread applications of electroporation in biotechnology and medicine, monitoring the distribution of deep tissue electrical fields in real-time during treatment continues to pose a challenge. Current medical imaging modalities are unable to monitor electroporation during pulse delivery. Here we propose a method to use electroacoustic tomography (EAT) to prompt the emission of broadband ultrasound waves via electrical energy deposition. EAT boasts submillimeter resolution at depths reaching 7.5 centimeters and can deliver imaging speeds up to 100 frames per second when paired with an ultrasound array system. We’ve successfully detected EAT signals at electric field strengths ranging from 60 volts per centimeter to several tens of kilovolts per centimeter. This establishes EAT as a potential label-free, high-resolution approach for real-time evaluation of deep tissue electroporation during therapeutic procedures.

Electroporation stimulated by pulsed electrical fields can increase the permeability of cell membranes. However, real-time monitoring of electroporation during pulse delivery is challenging. Xu and colleagues use electroacoustic tomography to image electrical field deposition in deep tissue. This label-free method achieves submillimeter resolution at depths up to 7.5 centimetres.

Optimal Dosing and Patient Selection for Electrochemotherapy in Solid Abdominal Organ and Bone Tumors

The primary aim of this study was to analyze studies that use electrochemotherapy (ECT) in "deep-seated" tumors in solid organs (liver, kidney, bone metastasis, pancreas, and abdomen) and understand the similarities between patient selection, oncologic selection, and use of new procedures and technology across the organ systems to assess response rates. A literature search was conducted using the term "Electrochemotherapy" in the title field using publications from 2017 to 2023. After factoring in inclusion and exclusion criteria, 29 studies were analyzed and graded based on quality in full. The authors determined key patient and oncologic selection characteristics and ECT technology employed across organ systems that yielded overall responses, complete responses, and partial responses of the treated tumor. It was determined that key selection factors included: the ability to be administered bleomycin, life expectancy greater than three months, unrespectability of the lesion being treated, and a later stage, more advanced cancer. Regarding oncologic selection, all patient cohorts had received chemotherapy or surgery previously but had disease recurrence, making ECT the only option for further treatment. Lastly, in terms of the use of technology, the authors found that studies with better response rates used the ClinporatorTM and updated procedural guidelines by SOP. Thus, by considering patient, oncologic, and technology selection, ECT can be further improved in treating lesions in solid organs.

Safety and Feasibility of Vulvar Cancer Treatment with Electrochemotherapy

Electrochemotherapy is a local ablative therapy used for the treatment of various superficial and deep-seated tumors. Electrochemotherapy involves the application of electric pulses locally to tumors to destabilize cell membranes and facilitate the entry of cytotoxic drugs, thereby enhancing their cytotoxicity locally. The aim of our study is to investigate the safety and feasibility of electrochemotherapy in patients with vulvar cancer recurrence used for nonpalliative purposes. Ten patients with single local vulvar cancer recurrence were treated with intravenous bleomycin, followed by a local application of electric pulses (electrochemotherapy) to the tumor. Adverse events were determined using the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The feasibility of treating vulvar cancer with electrochemotherapy was determined by an appropriate selection of electrodes based on the size and location of the tumor with safety margins included. Electrochemotherapy was feasible in all patients. No electrochemotherapy-related or other serious adverse events occurred. Our data suggest that electrochemotherapy is a feasible and safe technique for the treatment of vulvar cancer recurrence for nonpalliative purposes. Based on our results, electrochemotherapy might be a viable therapeutic tool for patients who would otherwise undergo surgery involving a mutilation of the external genitalia.

Immunogenic Cell Death in Electroporation-Based Therapies Depends on Pulse Waveform Characteristics

Traditionally, electroporation-based therapies such as electrochemotherapy (ECT), gene electrotransfer (GET) and irreversible electroporation (IRE) are performed with different but typical pulse durations-100 microseconds and 1-50 milliseconds. However, recent in vitro studies have shown that ECT, GET and IRE can be achieved with virtually any pulse duration (millisecond, microsecond, nanosecond) and pulse type (monopolar, bipolar-HFIRE), although with different efficiency. In electroporation-based therapies, immune response activation can affect treatment outcome, and the possibility of controlling and predicting immune response could improve the treatment. In this study, we investigated if different pulse durations and pulse types cause different or similar activations of the immune system by assessing DAMP release (ATP, HMGB1, calreticulin). Results show that DAMP release can be different when different pulse durations and pulse types are used. Nanosecond pulses seems to be the most immunogenic, as they can induce the release of all three main DAMP molecules-ATP, HMGB1 and calreticulin. The least immunogenic seem to be millisecond pulses, as only ATP release was detected and even that assumingly occurs due to increased permeability of the cell membrane. Overall, it seems that DAMP release and immune response in electroporation-based therapies can be controlled though pulse duration.

Effects of Electrochemotherapy on Immunologically Important Modifications in Tumor Cells

Electrochemotherapy (ECT) is a clinically acknowledged method that combines the use of anticancer drugs and electrical pulses. Electrochemotherapy with bleomycin (BLM) can induce immunogenic cell death (ICD) in certain settings. However, whether this is ubiquitous over different cancer types and for other clinically relevant chemotherapeutics used with electrochemotherapy is unknown. Here, we evaluated in vitro in the B16-F10, 4T1 and CT26 murine tumor cell lines, the electrochemotherapy triggered changes in the ICD-associated damage-associated molecular patterns (DAMPs): Calreticulin (CRT), ATP, High Mobility Group Box 1 (HMGB1), and four immunologically important cellular markers: MHCI, MHC II, PD-L1 and CD40. The changes in these markers were investigated in time up to 48 h after ECT. We showed that electrochemotherapy with all three tested chemotherapeutics induced ICD-associated DAMPs, but the induced DAMP signature was cell line and chemotherapeutic concentration specific. Similarly, electrochemotherapy with CDDP, OXA or BLM modified the expression of MHC I, MHC II, PD-L1 and CD40. The potential of electrochemotherapy to change their expression was also cell line and chemotherapeutic concentration specific. Our results thus put the electrochemotherapy with clinically relevant chemotherapeutics CDDP, OXA and BLM on the map of ICD inducing therapies.

Evaluation of Electrochemotherapy with Bleomycin in the Treatment of Colorectal Hepatic Metastases in a Rat Model

BACKGROUND

The available ablative procedures for the treatment of hepatic cancer have contraindications due to the heat-sink effect and the risk of thermal injuries. Electrochemotherapy (ECT) as a nonthermal approach may be utilized for the treatment of tumors adjacent to high-risk regions. We evaluated the effectiveness of ECT in a rat model.

METHODS

WAG/Rij rats were randomized to four groups and underwent ECT, reversible electroporation (rEP), or intravenous injection of bleomycin (BLM) eight days after subcapsular hepatic tumor implantation. The fourth group served as Sham. Tumor volume and oxygenation were measured before and five days after the treatment using ultrasound and photoacoustic imaging; thereafter, liver and tumor tissue were additionally analysed by histology and immunohistochemistry.

RESULTS

The ECT group showed a stronger reduction in tumor oxygenation compared to the rEP and BLM groups; moreover, ECT-treated tumors exhibited the lowest levels of hemoglobin concentration compared to the other groups. Histological analyses further revealed a significantly increased tumor necrosis of >85% and a reduced tumor vascularization in the ECT group compared to the rEP, BLM, and Sham groups.

CONCLUSION

ECT is an effective approach for the treatment of hepatic tumors with necrosis rates >85% five days following treatment.

Canine squamous cell carcinoma: Electrochemotherapy association with surgery and correlation with overall survival

Squamous cell carcinoma (SCC) is an important malignancy in dogs, due to its incidence and clinical presentation, which can be of locally aggressive single or multiple lesions with a metastatic potential. The objective of this investigation was to evaluate SCC response to treatment, anatomopathological and immunohistochemical characteristics, disease-free interval and overall survival time. 54 dogs with histopathologically diagnosed SCC were included in this study. Their mean age was 9.16 years with a range of 1-14 years. Of the 54 animals in the study, 34 (65.4%) had white skin and white fur coats. There was a significant correlation between fur coat colour and the development of tumours in areas of sun exposure (p = .001). Animals with tumours in areas of the body exposed to the sun had longer overall survival time than animals with tumours in areas not associated with sun exposure (p = .001). Surgery combined with electrochemotherapy (ECT) yielded a survival rate 32% higher than using a surgical approach alone (HR = 0.32, p = .038, IC = 0.11-0.94). ECT, with or without surgery, had an objective response rate of 90.9%. Local lymph node and/or distant site metastasis at diagnosis, or at some point during follow-up, occurred in 34.6% (18/52) of animals. Animals with tumours in sun exposed locations had more aggressive histopathological characteristics but had longer overall survival time. This is probably due to individualised therapeutic treatment with both surgery and ECT.

Invasive and non-invasive electrodes for successful drug and gene delivery in electroporation-based treatments

Electroporation is an effective physical method for irreversible or reversible permeabilization of plasma membranes of biological cells and is typically used for tissue ablation or targeted drug/DNA delivery into living cells. In the context of cancer treatment, full recovery from an electroporation-based procedure is frequently dependent on the spatial distribution/homogeneity of the electric field in the tissue; therefore, the structure of electrodes/applicators plays an important role. This review focuses on the analysis of electrodes and in silico models used for electroporation in cancer treatment and gene therapy. We have reviewed various invasive and non-invasive electrodes; analyzed the spatial electric field distribution using finite element method analysis; evaluated parametric compatibility, and the pros and cons of application; and summarized options for improvement. Additionally, this review highlights the importance of tissue bioimpedance for accurate treatment planning using numerical modeling and the effects of pulse frequency on tissue conductivity and relative permittivity values.

Advances of Electroporation-Related Therapies and the Synergy with Immunotherapy in Cancer Treatment

Electroporation is the process of instantaneously increasing the permeability of a cell membrane under a pulsed electric field. Depending on the parameters of the electric pulses and the target cell electrophysiological characteristics, electroporation can be either reversible or irreversible. Reversible electroporation facilitates the delivery of functional genetic materials or drugs to target cells, inducing cell death by apoptosis, mitotic catastrophe, or pseudoapoptosis; irreversible electroporation is an ablative technology which directly ablates a large amount of tissue without causing harmful thermal effects; electrotherapy using an electric field can induce cell apoptosis without any aggressive invasion. Reversible and irreversible electroporation can also activate systemic antitumor immune response and enhance the efficacy of immunotherapy. In this review, we discuss recent progress related to electroporation, and summarize its latest applications. Further, we discuss the synergistic effects of electroporation-related therapies and immunotherapy. We also propose perspectives for further investigating electroporation and immunotherapy in cancer treatment.

Electrochemically Enhanced Delivery of Pemetrexed from Electroactive Hydrogels

Electroactive hydrogels based on derivatives of polyethyleneglycol (PEG), chitosan and polypyrrole were prepared via a combination of photopolymerization and oxidative chemical polymerization, and optionally doped with anions (e.g., lignin, drugs, etc.). The products were analyzed with a variety of techniques, including: FT-IR, UV-Vis, ¹H NMR (solution state), ¹³C NMR (solid state), XRD, TGA, SEM, swelling ratios and rheology. The conductive gels swell ca. 8 times less than the non-conductive gels due to the presence of the interpenetrating network (IPN) of polypyrrole and lignin. A rheological study showed that the non-conductive gels are soft (G' 0.35 kPa, G″ 0.02 kPa) with properties analogous to brain tissue, whereas the conductive gels are significantly stronger (G' 30 kPa, G″ 19 kPa) analogous to breast tissue due to the presence of the IPN of polypyrrole and lignin. The potential of these biomaterials to be used for biomedical applications was validated in vitro by cell culture studies (assessing adhesion and proliferation of fibroblasts) and drug delivery studies (electrochemically loading the FDA-approved chemotherapeutic pemetrexed and measuring passive and stimulated release); indeed, the application of electrical stimulus enhanced the release of PEM from gels by ca. 10-15% relative to the passive release control experiment for each application of electrical stimulation over a short period analogous to the duration of stimulation applied for electrochemotherapy. It is foreseeable that such materials could be integrated in electrochemotherapeutic medical devices, e.g., electrode arrays or plates currently used in the clinic.

Laparoscopic electrochemotherapy for the treatment of hepatocellular carcinoma: Technological advancement

Electrochemotherapy is an effective treatment modality for hepatocellular carcinoma (HCC). Electrochemotherapy for HCC was initially used in the setting of open surgery. Recently, with the development of newer electrodes, percutaneous approaches have also been performed. However, laparoscopic application of electrochemotherapy for HCC has not yet been described. Two patients with unresectable HCC were enrolled in the study. The first patient was not suitable for the percutaneous approach because the tumor was located close to the gallbladder. He also had symptomatic gallstones. The second patient had HCC in close proximity to the stomach and was therefore not suitable for percutaneous access or any other ablative technique. Thus, the laparoscopic approach was chosen, using newly developed Stinger electrodes for the application of electric pulses. After intravenous administration of bleomycin, several sets of electric pulses were delivered to the whole tumor mass in both patients. Ultrasonographically, the coverage of the whole tumor was verified, as described previously. Cholecystectomy was also performed in the first patient. Follow-up abdominal computed tomography showed a complete response of the treated lesions in both patients. Minimally invasive laparoscopic electrochemotherapy is safe, feasible and effective method for the treatment of HCC. It could be used in patients in whom the percutaneous approach is unsafe (proximity to other organs) and in patients with concomitant symptomatic gallstones in whom cholecystectomy is already indicated. This technological approach thus allows broader and minimally invasive clinical applicability of electrochemotherapy.

Optimization of Transpedicular Electrode Insertion for Electroporation-Based Treatments of Vertebral Tumors

Electroporation-based treatments such as electrochemotherapy and irreversible electroporation ablation have sparked interest with respect to their use in medicine. Treatment planning involves determining the best possible electrode positions and voltage amplitudes to ensure treatment of the entire clinical target volume (CTV). This process is mainly performed manually or with computationally intensive genetic algorithms. In this study, an algorithm was developed to optimize electrode positions for the electrochemotherapy of vertebral tumors without using computationally intensive methods. The algorithm considers the electric field distribution in the CTV, identifies undertreated areas, and uses this information to iteratively shift the electrodes from their initial positions to cover the entire CTV. The algorithm performs successfully for different spinal segments, tumor sizes, and positions within the vertebra. The average optimization time was 71 s with an average of 4.9 iterations performed. The algorithm significantly reduces the time and expertise required to create a treatment plan for vertebral tumors. This study serves as a proof of concept that electrode positions can be determined (semi-)automatically based on the spatial information of the electric field distribution in the target tissue. The algorithm is currently designed for the electrochemotherapy of vertebral tumors via a transpedicular approach but could be adapted for other anatomic sites in the future.

Nanosecond PEF Induces Oxidative Stress and Apoptosis via Proteasomal Activity Inhibition in Gastric Adenocarcinoma Cells with Drug Resistance

Nanosecond (ns) pulsed electric field (PEF) is a technology in which the application of ultra-short electrical pulses can be used to disrupt the barrier function of cell plasma and internal membranes. Disruptions of the membrane integrity cause a substantial imbalance in cell homeostasis in which oxidative stress is a principal component. In the present study, nsPEF-induced oxidative stress was investigated in two gastric adenocarcinoma cell lines (EPG85-257P and EPG85-257RDB) which differ by their sensitivity to daunorubicin. Cells were exposed to 200 pulses of 10 ns duration, with the amplitude and pulse repetition frequency at 1 kHz, with electric field intensity varying from 12.5 to 50 kV/cm. The electroporation buffer contained either 1 mM or 2 mM calcium chloride. CellMask DeepRed visualized cell plasma permeabilization, Fluo-4 was used to visualize internal calcium ions content, and F-actin was labeled with AlexaFluor^®488 for the cytoskeleton. The cellular viability was determined by MTT assay. An alkaline and neutral comet assay was employed to detect apoptotic and necrotic cell death. The luminescent method estimated the modifications in GSSG/GSH redox potential and the imbalance of proteasomal activity (chymotrypsin-, trypsin- and caspase-like). The reactive oxygen species (ROS) level was measured by flow cytometry using dihydroethidium (DHE) dye. Morphological visualization indicated cell shrinkage, affected cell membranes (characteristic bubbles and changed cell shape), and the reorganization of actin fibers with sites of its dense concentration; the effect was more intense with the increasing electric field strength. The most significant decrease in cell viability and GSSG/GSH redox potential was noted at the highest amplitude of 50 kV/cm, and calcium ions amplified this effect. nsPEF, particularly with calcium ions, inhibited proteasomal activities, resulting in increased protein degradation. nsPEF increased the percentage of apoptotic cells and ROS levels. The EPG85-257 RDB cell line, which is resistant to standard chemotherapy, was more sensitive to applied nsPEF protocols. The applied nsPEF method disrupted the metabolism of cancer cells and induced apoptotic cell death. The nsPEF ability to cause apoptosis, oxidative stress, and protein degradation make the nsPEF methodology a suitable alternative to current anticancer pharmacological methods.

Electrochemotherapy: An Alternative Strategy for Improving Therapy in Drug-Resistant SOLID Tumors

Simple Summary

Chemotherapy is becoming an increasingly difficult antitumor therapy to practice due to the multiple mechanisms of drug resistance. To overcome the problem, it is possible to use alternative techniques, such as electrochemotherapy, which involves the simultaneous administration of the electrical pulse (electroporation) and the treatment with the drug in order to improve the effectiveness of the drug against the tumor. Electroporation has improved the efficacy of some chemotherapeutic agents, such bleomycin, cisplatin, mitomycin C, and 5-fluorouracil. The results of in vitro, veterinary, and clinical oncology studies are promising on various cancers, such as metastatic melanoma. The purpose of this review is to give an update on the state of the art of electrochemotherapy against the main solid tumors in the preclinical, clinical, and veterinary field.

Abstract

Electrochemotherapy (ECT) is one of the innovative strategies to overcome the multi drug resistance (MDR) that often occurs in cancer. Resistance to anticancer drugs results from a variety of factors, such as genetic or epigenetic changes, an up-regulated outflow of drugs, and various cellular and molecular mechanisms. This technology combines the administration of chemotherapy with the application of electrical pulses, with waveforms capable of increasing drug uptake in a non-toxic and well tolerated mechanical system. ECT is used as a first-line adjuvant therapy in veterinary oncology, where it improves the efficacy of many chemotherapeutic agents by increasing their uptake into cancer cells. The chemotherapeutic agents that have been enhanced by this technique are bleomycin, cisplatin, mitomycin C, and 5-fluorouracil. After their use, a better localized control of the neoplasm has been observed. In humans, the use of ECT was initially limited to local palliative therapy for cutaneous metastases of melanoma, but phase I/II studies are currently ongoing for several histotypes of cancer, with promising results. In this review, we described the preclinical and clinical use of ECT on drug-resistant solid tumors, such as head and neck squamous cell carcinoma, breast cancer, gynecological cancer and, finally, colorectal cancer.

Nanosecond electric pulses are equally effective in electrochemotherapy with cisplatin as microsecond pulses

BACKGROUND

Nanosecond electric pulses showed promising results in electrochemotherapy, but the underlying mechanisms of action are still unexplored. The aim of this work was to correlate cellular cisplatin amount with cell survival of cells electroporated with nanosecond or standardly used 8 × 100 μs pulses and to investigate the effects of electric pulses on cisplatin structure.

MATERIALS AND METHODS

Chinese hamster ovary CHO and mouse melanoma B16F1 cells were exposed to 1 × 200 ns pulse at 12.6 kV/cm or 25 × 400 ns pulses at 3.9 kV/cm, 10 Hz repetition rate or 8 × 100 μs pulses at 1.1 (CHO) or 0.9 (B16F1) kV/cm, 1 Hz repetition rate at three cisplatin concentrations. Cell survival was determined by the clonogenic assay, cellular platinum was measured by inductively coupled plasma mass spectrometry. Effects on the structure of cisplatin were investigated by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.

RESULTS

Nanosecond pulses equivalent to 8 × 100 μs pulses were established in vitro based on membrane permeabilization and cell survival. Equivalent nanosecond pulses were equally efficient in decreasing the cell survival and accumulating cisplatin intracellularly as 8 × 100 μs pulses after electrochemotherapy. The number of intracellular cisplatin molecules strongly correlates with cell survival for B16F1 cells, but less for CHO cells, implying the possible involvement of other mechanisms in electrochemotherapy. The high-voltage electric pulses did not alter the structure of cisplatin.

CONCLUSIONS

Equivalent nanosecond pulses are equally effective in electrochemotherapy as standardly used 8 × 100 μs pulses.

Health-related quality of life trajectories in melanoma patients after electrochemotherapy: real-world insights from the InspECT register

BACKGROUND

Electrochemotherapy (ECT) effectively controls skin metastases from cutaneous melanoma.

OBJECTIVES

This study aimed to evaluate health-related quality of life (HRQoL) in melanoma patients pre-/post-ECT and its effect on treatment outcome.

METHODS

The analysis included prospective data from the International Network for Sharing Practices of ECT register. Following the Standard Operating Procedures, patients received intravenous or intratumoural bleomycin (15,000 IU/m2 ; 1000 IU mL/cm3 ) followed by 100-microsecond, 1000-V/cm electric pulses. Endpoints included response (RECIST v3.0), local progression-free survival (LPFS), toxicity (CTCAE v5.0), and patient-reported HRQoL at baseline, one, two, four and ten months (EuroQol [EQ-5D-3L], including 5-item utility score [EQ-5D] and visual analogue scale for self-reported health state [EQ-VAS]). Comparisons within/between subgroups were made for statistical and minimal important differences (MID). HRQoL scores and clinical covariates were analysed to identify predictors of response in multivariate analysis.

RESULTS

Median tumour size was 2 cm. Complete response rate, G3 toxicity and one-year LPFS in 378 patients (76% of the melanoma cohort) were 47%, 5%, and 78%. At baseline, age-paired HRQoL did not differ from the general European population. Following ECT, both EQ-5D and EQ-VAS scores remained within MID boundaries, particularly among complete responders. A subanalysis of the EQ-5D items revealed a statistically significant deterioration in pain/discomfort and mobility (restored within four months), and self-care and usual activities (throughout the follow-up) domains. Concomitant checkpoint inhibition correlated with better EQ-5D and EQ-VAS trajectories. Baseline EQ-5D was the exclusive independent predictor for complete response (RR 14.76, p=0.001).

CONCLUSIONS

HRQoL of ECT melanoma patients parallels the general population and is preserved in complete responders. Transient deterioration in pain/discomfort and mobility and persistent decline in self-care and usual activities may warrant targeted support interventions. Combination with checkpoint inhibitors is associated with better QoL outcomes. Baseline HRQoL provides predictive information which can help identify patients most likely to respond.

Electroporation and Immunotherapy-Unleashing the Abscopal Effect

Simple Summary

Electrochemotherapy and irreversible electroporation are primarily used for treating patients with cutaneous and subcutaneous tumors and pancreatic cancer, respectively. Increasing numbers of studies have shown that the treatments may elicit an immune response in addition to eliminating the tumor cells. The purpose of this review is to give an in-depth introduction to the electroporation-induced immune response and the local and peripheral immune systems, and to describe the various studies investigating the combination of electroporation and immunotherapy. The review may help guide and inspire the design of future clinical trials investigating the potential synergy of electroporation and immunotherapy in cancer treatment.

Abstract

The discovery of electroporation in 1968 has led to the development of electrochemotherapy (ECT) and irreversible electroporation (IRE). ECT and IRE have been established as treatments of cutaneous and subcutaneous tumors and locally advanced pancreatic cancer, respectively. Interestingly, the treatment modalities have been shown to elicit immunogenic cell death, which in turn can induce an immune response towards the tumor cells. With the dawn of the immunotherapy era, the potential of combining ECT and IRE with immunotherapy has led to the launch of numerous studies. Data from the first clinical trials are promising, and new combination regimes might change the way we treat tumors characterized by low immunogenicity and high levels of immunosuppression, such as melanoma and pancreatic cancer. In this review we will give an introduction to ECT and IRE and discuss the impact on the immune system. Additionally, we will present the results of clinical and preclinical trials, investigating the combination of electroporation modalities and immunotherapy.

Nanosecond Pulsed Electric Field (nsPEF): Opening the Biotechnological Pandora’s Box

Nanosecond Pulsed Electric Field (nsPEF) is an electrostimulation technique first developed in 1995; nsPEF requires the delivery of a series of pulses of high electric fields in the order of nanoseconds into biological tissues or cells. They primary effects in cells is the formation of membrane nanopores and the activation of ionic channels, leading to an incremental increase in cytoplasmic Ca2+ concentration, which triggers a signaling cascade producing a variety of effects: from apoptosis up to cell differentiation and proliferation. Further, nsPEF may affect organelles, making nsPEF a unique tool to manipulate and study cells. This technique is exploited in a broad spectrum of applications, such as: sterilization in the food industry, seed germination, anti-parasitic effects, wound healing, increased immune response, activation of neurons and myocites, cell proliferation, cellular phenotype manipulation, modulation of gene expression, and as a novel cancer treatment. This review thoroughly explores both nsPEF’s history and applications, with emphasis on the cellular effects from a biophysics perspective, highlighting the role of ionic channels as a mechanistic driver of the increase in cytoplasmic Ca2+ concentration.

Muscle contractions and pain sensation accompanying high-frequency electroporation pulses

To minimize neuromuscular electrical stimulation during electroporation-based treatments, the replacement of long monophasic pulses with bursts of biphasic high-frequency pulses in the range of microseconds was suggested in order to reduce muscle contraction and pain sensation due to pulse application. This treatment modality appeared under the term high-frequency electroporation (HF-EP), which can be potentially used for some clinical applications of electroporation such as electrochemotherapy, gene electrotransfer, and tissue ablation. In cardiac tissue ablation, which utilizes irreversible electroporation, the treatment is being established as Pulsed Field Ablation. While the reduction of muscle contractions was confirmed in multiple in vivo studies, the reduction of pain sensation in humans was not confirmed yet, nor was the relationship between muscle contraction and pain sensation investigated. This is the first study in humans examining pain sensation using biphasic high-frequency electroporation pulses. Twenty-five healthy individuals were subjected to electrical stimulation of the tibialis anterior muscle with biphasic high-frequency pulses in the range of few microseconds and both, symmetric and asymmetric interphase and interpulse delays. Our results confirm that biphasic high-frequency pulses with a pulse width of 1 or 2 µs reduce muscle contraction and pain sensation as opposed to currently used longer monophasic pulses. In addition, interphase and interpulse delays play a significant role in reducing the muscle contraction and/or pain sensation. The study shows that the range of the optimal pulse parameters may be increased depending on the prerequisites of the therapy. However, further evaluation of the biphasic pulse protocols presented herein is necessary to confirm the efficiency of the newly proposed HF-EP.

Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma

BACKGROUND

 Hepatocellular carcinoma (HCC) is the fifth most common tumor worldwide. Because many hepatocellular carcinomas are already unresectable at the time of initial diagnosis, percutaneous tumor ablation has become established in recent decades as a curative therapeutic approach for very early (BCLC 0) and early (BCLC A) HCC. The aim of this paper is to provide a concise overview of the percutaneous local ablative procedures currently in use, based on their technical characteristics as well as clinical relevance, taking into account the current body of studies.

MATERIALS AND METHODS

 The literature search included all original papers, reviews, and meta-analyses available via MEDLINE and Pubmed on the respective percutaneous ablation procedures; the primary focus was on randomized controlled trials and publications from the last 10 years.

RESULTS AND CONCLUSIONS

 Radiofrequency ablation (RFA) and microwave ablation (MWA) are well-established procedures that are considered equal to surgical resection in the treatment of stage BCLC 0 and A HCC with a diameter up to 3 cm due to their strong evidence in international and national guidelines. For tumors with a diameter between 3 and 5 cm, the current S3 guidelines recommend a combination of transarterial chemoembolization (TACE) and thermal ablation using RFA or MWA as combination therapy is superior to thermal ablation alone in tumors of this size and shows comparable results to surgical resection in terms of overall survival. Alternative, less frequently employed thermal procedures include cryotherapy (CT) and laser ablation (LA). Non-thermal procedures include irreversible electroporation (IRE), interstitial brachytherapy (IBT), and most recently, electrochemotherapy (ECT). Due to insufficient evidence, these have only been used in individual cases and within the framework of studies. However, the nonthermal methods are a reasonable alternative for ablation of tumors adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods. With advances in the technology of the respective procedures, increasingly good evidence, and advancements in supportive techniques such as navigation devices and fusion imaging, percutaneous ablation procedures may expand their indications for the treatment of larger and more advanced tumors in the coming years.

KEY POINTS

· RFA and MWA are considered equal to surgical resection as a first-line therapy for the curative treatment of stage BCLC 0 and A HCCs with a diameter of up to 3 cm.. · For HCCs with a diameter between 3 and 5 cm, a combination of TACE and RFA or MWA is recommended. This combination therapy yields results comparable to those of surgical resection in terms of overall survival.. · Due to insufficient evidence, alternative ablation methods have only been used in individual cases and within the framework of studies. However, nonthermal methods, such as IRE, IBT, and, most recently, ECT, are a reasonable alternative for ablation of HCCs adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods..

CITATION FORMAT

· Luerken L, Haimerl M, Doppler M et al. Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1768-0954.

Numerical mesoscale tissue model of electrochemotherapy in liver based on histological findings

Electrochemotherapy (ECT) and irreversible electroporation (IRE) are being investigated for treatment of hepatic tumours. The liver is a highly heterogeneous organ, permeated with a network of macro- and microvasculature, biliary tracts and connective tissue. The success of ECT and IRE depends on sufficient electric field established in whole target tissue; therefore, tissue heterogeneity may affect the treatment outcome. In this study, we investigate electroporation in the liver using a numerical mesoscale tissue model. We numerically reconstructed four ECT experiments in healthy porcine liver and computed the electric field distribution using our treatment planning framework. We compared the computed results with histopathological changes identified on microscopic images after treatment. The mean electric field threshold that best fitted the zone of coagulation necrosis was 1225 V/cm, while the mean threshold that best fitted the zone of partially damaged liver parenchyma attributed to IRE was 805 V/cm. We evaluated how the liver macro- and microstructures affect the electric field distribution. Our results show that the liver microstructure does not significantly affect the electric field distribution on the level needed for treatment planning. However, major hepatic vessels and portal spaces significantly affect the electric field distribution, and should be considered when planning treatments.

‘Breast Cancer Resistance Likelihood and Personalized Treatment Through Integrated Multiomics’

In recent times, enormous progress has been made in improving the diagnosis and therapeutic strategies for breast carcinoma, yet it remains the most prevalent cancer and second highest contributor to cancer-related deaths in women. Breast cancer (BC) affects one in eight females globally. In 2018 alone, 1.4 million cases were identified worldwide in postmenopausal women and 645,000 cases in premenopausal females, and this burden is constantly increasing. This shows that still a lot of efforts are required to discover therapeutic remedies for this disease. One of the major clinical complications associated with the treatment of breast carcinoma is the development of therapeutic resistance. Multidrug resistance (MDR) and consequent relapse on therapy are prevalent issues related to breast carcinoma; it is due to our incomplete understanding of the molecular mechanisms of breast carcinoma disease. Therefore, elucidating the molecular mechanisms involved in drug resistance is critical. For management of breast carcinoma, the treatment decision not only depends on the assessment of prognosis factors but also on the evaluation of pathological and clinical factors. Integrated data assessments of these multiple factors of breast carcinoma through multiomics can provide significant insight and hope for making therapeutic decisions. This omics approach is particularly helpful since it identifies the biomarkers of disease progression and treatment progress by collective characterization and quantification of pools of biological molecules within and among the cancerous cells. The scrupulous understanding of cancer and its treatment at the molecular level led to the concept of a personalized approach, which is one of the most significant advancements in modern oncology. Likewise, there are certain genetic and non-genetic tests available for BC which can help in personalized therapy. Genetically inherited risks can be screened for personal predisposition to BC, and genetic changes or variations (mutations) can also be identified to decide on the best treatment. Ultimately, further understanding of BC at the molecular level (multiomics) will define more precise choices in personalized medicine. In this review, we have summarized therapeutic resistance associated with BC and the techniques used for its management.

Electroporation and Electrochemotherapy in Gynecological and Breast Cancer Treatment

Gynecological carcinomas affect an increasing number of women and are associated with poor prognosis. The gold standard treatment plan is mainly based on surgical resection and subsequent chemotherapy with cisplatin, 5-fluorouracil, anthracyclines, or taxanes. Unfortunately, this treatment is becoming less effective and is associated with many side effects that negatively affect patients’ physical and mental well-being. Electroporation based on tumor exposure to electric pulses enables reduction in cytotoxic drugs dose while increasing their effectiveness. EP-based treatment methods have received more and more interest in recent years and are the subject of a large number of scientific studies. Some of them show promising therapeutic potential without using any cytotoxic drugs or molecules already present in the human body (e.g., calcium electroporation). This literature review aims to present the fundamental mechanisms responsible for the course of EP-based therapies and the current state of knowledge in the field of their application in the treatment of gynecological neoplasms.

Polyoxometalate Modified by Zeolite Imidazole Framework for the pH-Responsive Electrodynamic/Chemodynamic Therapy

Electrodynamic therapy (EDT) and chemodynamic therapy (CDT) have the potential for future tumor treatment; however, their underlying applications are greatly hindered owing to their inherent drawbacks. The combination of EDT and CDT has been considered to be an effective way to maximize the superiorities of these two ROS-based methodologies. However, the development of novel nanomaterials with "one-for-all" functions still remains a big challenge. In this work, the polyoxometalate nanoparticles (NPs) were decorated using the zeolite imidazole framework (POM@ZIF-8) in order to integrate the EDT with CDT. The resulting POM@ZIF-8 NPs can effectively induce the generation of reactive oxygen species (ROS) via a catalytic reaction on the surface of POM NPs induced by an electric field (E). At the same time, POM@ZIF-8 NPs can catalyze the intracellular H₂O₂ into ROS via a Fenton-like reaction, thereby achieving the combination of EDT and CDT. Besides, since ZIF-8 is acid-responsive, it can protect normal tissues and avoid side effects. Of great note is that the cytotoxicity and the apoptosis rate of the POM@ZIF-8+E group (80%) were found to be significantly higher than that of the E group (55%). As a result, a high tumor inhibition phenomenon can be observed both in vitro and in vivo. The present study thus provides an alternative concept for combinational therapeutic modality with exceptional efficacy.