Calcium Delivery by Electroporation Induces In Vitro Cell Death through Mitochondrial Dysfunction without DNA Damages

Mitochondrial depolarization and ATP loss during high frequency nanosecond and microsecond electroporation

It is predicted that ultra-short electric field pulses (nanosecond) can selectively permeabilize intracellular structures (e.g., mitochondria) without significant effects on the outer cell plasma membrane. Such a phenomenon would have high applicability in cancer treatment and could be employed to modulate cell death type or immunogenic response. Therefore, in this study, we compare the effects of 100 µs x 8 pulses (ESOPE - European Standard Operating Procedures on Electrochemotherapy) and bursts of 100 ns pulses for modulation of the mitochondria membrane potential. We characterize the efficacies of various protocols to trigger permeabilization, depolarize mitochondria (evaluated 1 h  after treatment), the extent of ATP depletion and generation of reactive oxygen species (ROS). Finally, we employ the most prominent protocols in the context of Ca2+ electrochemotherapy in vitro. We provide experimental proof that 7.5-12.5 kV/cm x 100 ns pulses can be used to modulate mitochondrial potential, however, the permeabilization of the outer membrane is still a prerequisite for depolarization. Similar to 100 µs x 8 pulses, the higher the permeabilization rate, the higher the mitochondrial depolarization. Nevertheless, 100 ns pulses result in lesser ROS generation when compared to ESOPE, even when the energy input is several-fold higher than for the microsecond procedure. At the same time, it shows that even the short 100 ns pulses can be successfully used for Ca2+ electrochemotherapy, ensuring excellent cytotoxic efficacy.

Encapsulation of photosensitizer worsen cell responses after photodynamic therapy protocol and polymer micelles act as biomodulators on their own

Photodynamic therapy (PDT) is a photochemical therapeutic modality used clinically for dermatological, ophthalmological and oncological applications. Pheo a was used as a model photosensitizer, either in its free form or encapsulated within poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-PCL) polymer micelles. Block copolymer micelles are water-soluble biocompatible nanocontainers with great potential for delivering hydrophobic drugs. Empty PEO-PCL micelles were also tested throughout the experiments. The goal was to conduct an in vitro investigation into human colorectal tumor HCT-116 cellular responses induced by free and encapsulated Pheo a in terms of cell architecture, plasma membrane exchanges, mitochondrial function, and metabolic disturbances. In a calibrated PDT protocol, encapsulation enhanced Pheo a penetration (flow cytometry, confocal microscopy) and cell death (Prestoblue assay), causing massive changes to cell morphology (SEM) and cytoskeleton organization (confocal), mitochondrial dysfunction and loss of integrity (TEM), rapid and massive ion fluxes across the plasma membrane (ICP-OES, ion chromatography), and metabolic alterations, including increased levels of amino acids and choline derivatives (1H NMR). The detailed investigation provides insights into the multifaceted effects of encapsulated Pheo-PDT, emphasizing the importance of considering both the photosensitizer and its delivery system in understanding therapeutic outcomes. The study also raises questions as to the broader impact of empty nanovectors per se, and encourages a more comprehensive exploration of their biological effects.

Electrochemotherapy and Calcium Electroporation on Hepatocellular Carcinoma Cells: An In-Vitro Investigation

PURPOSE

Electrochemotherapy, clinically established for treating (sub)cutaneous tumors, has been standardized in the framework of the European Standard Operating Procedure on Electrochemotherapy (ESOPE). Due to common side effects of chemotherapeutic drugs, recent advances focus on non-cytotoxic agents, like calcium, to induce cell death (calcium electroporation). Therefore, this study aims to determine the efficacy of electrochemotherapy with bleomycin or cisplatin, or calcium electroporation on human hepatocellular carcinoma cells (HepG2) in vitro using the ESOPE protocol.

METHODS

HepG2 cell viability was measured with a MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay after electrochemotherapy with the chemotherapeutic drugs bleomycin or cisplatin (0-20 µM), or after calcium electroporation (0-20 mM), to determine its efficacy on HepG2 cells in vitro using the ESOPE protocol (8 rectangular pulses, 1000 V/cm, 100 µs) compared to non-electroporated drug treatment.

RESULTS

Cell viability was significantly lower in electroporated samples, compared to their non-electroporated controls (27-75% difference). Electrochemotherapy with bleomycin and calcium electroporation, reached (almost) complete cell death (- 1 ± 3% and 2.5 ± 2%), in the lowest concentration of 2.5 µM and 2.5 mM, respectively. Electrochemotherapy with 2.5 µM cisplatin, significantly decreased cell viability to only 68% (± 7%).

CONCLUSION

Electrochemotherapy with bleomycin or cisplatin, or calcium electroporation were more effective in reducing the HepG2 cell viability in vitro using the ESOPE protocol compared to the non-electroporated drug treatments alone. When comparing electrochemotherapy, HepG2 cells are more sensitive to bleomycin than cisplatin, in similar concentrations. Calcium electroporation has the same effectiveness as electrochemotherapy with bleomycin, but calcium potentially has a better safety profile and several treatment advantages.

Effects of buffer composition and plasmid toxicity on electroporation-based non-viral gene delivery in mammalian cells using bursts of nanosecond and microsecond pulses

Gene electrotransfer (GET) is non-viral gene delivery technique, also known as electroporation-mediated gene delivery or electrotransfection. GET is a method used to introduce foreign genetic material (such as DNA or RNA) into cells by applying external pulsed electric fields (PEFs) to create temporary pores in the cell membrane. This study was undertaken to examine the impact of buffer composition on the efficiency of GET in mammalian cells Also, we specifically compared the effectiveness of high-frequency nanosecond (ns) pulses with standard microsecond (µs) pulses. For the assessment of cell transfection efficiency and viability, flow cytometric analysis, luminescent assays, and measurements of metabolic activity were conducted. The efficiency of electrotransfection was evaluated using two different proteins encoding plasmids (pEGFP-N1 and Luciferase-pcDNA3). The investigation revealed that the composition of the electroporation buffer significantly influences the efficacy of GET in CHO-K1 cell line. The different susceptibility of cell lines to the electric field and the plasmid cytotoxicity were reported. It was also shown that electroporation with nanosecond duration PEF protocols ensured equivalent or even better transfection efficiency than standard µsPEF. Additionally, we successfully performed long-term transfection of the murine 4T1 cell line using high-frequency nanosecond PEFs and confirmed its' applicability in an in vivo model. The findings from the study can be applied to optimize electrotransfection conditions.

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.

An Explorative Study on Calcium Electroporation for Low-risk Basal Cell Carcinoma

In electrochemotherapy, permeabilization of the cell membrane by electric pulses increases the anti-tumour effect of chemotherapeutics. In calcium electroporation, chemotherapy is replaced by calcium chloride with obvious benefits. This study explores the effect and underlying mechanisms of calcium electroporation on basal cell carcinomas using either high- or low-frequency electroporation. Low-risk primary basal cell carcinomas were treated in local anaesthesia with intratumoral calcium chloride followed by electroporation with high (167 kHz) or low (5 kHz) frequencies. Non-complete responders were retreated after 3 months. The primary endpoint was tumour response 3 months after last calcium electroporation. Plasma membrane calcium ATPase was examined in various cell lines as plasma membrane calcium ATPase levels have been associated with calcium electroporation efficacy. Twenty-two out of 25 included patients complete the study and 7 of these (32%) achieved complete response at 3 months with no difference in efficacy between high- and low-frequency pulses. High-frequency calcium electroporation was significantly less painful (p=0.03). Plasma membrane calcium ATPase was increased 16-32-fold in basal cell carcinoma cell lines compared with 4 other cancer cell lines. Calcium electroporation for low-risk basal cell carcinomas does not fulfil the requirements of a new dermatological basal cell carcinoma treatment but may be useful as adjuvant treatment to surgery in more advanced basal cell carcinomas. The elevated PMCA levels in basal cell carcinomas may contribute to low efficacy.

Electrolysis products, reactive oxygen species and ATP loss contribute to cell death following irreversible electroporation with microsecond-long pulsed electric fields

Membrane permeabilization and thermal injury are the major cause of cell death during irreversible electroporation (IRE) performed using high electric field strength (EFS) and small number of pulses. In this study, we explored cell death under conditions of reduced EFS and prolonged pulse application, identifying the contributions of electrolysis, reactive oxygen species (ROS) and ATP loss. We performed ablations with conventional high-voltage low pulse (HV-LP) and low-voltage high pulse (LV-HP) conditions in a 3D tumor mimic, finding equivalent ablation volumes when using 2000 V/cm 90 pulses or 1000 V/cm 900 pulses respectively. These results were confirmed by performing ablations in swine liver. In LV-HP treatment, ablation volume was found to increase proportionally with pulse numbers, without the substantial temperature increase seen with HV-LP parameters. Peri-electrode pH changes, ATP loss and ROS production were seen in both conditions, but LV-HP treatments were more sensitive to blocking of these forms of cell injury. Increases in current drawn during HV-LP was not observed during LV-HP condition where the total ablation volume correlated to the charge delivered into the tissue which was greater than HV-LP treatment. LV-HP treatment provides a new paradigm in using pulsed electric fields for tissue ablation with clinically relevant volumes.

Calcium electroporation in cutaneous metastases - A non-randomised phase II multicentre clinical trial

BACKGROUND

Cutaneous metastases can cause distressing symptoms and be challenging to treat. Local therapies are essential in management. Calcium electroporation uses calcium and electrical pulses to selectively kill cancer cells. This multicentre study aimed to define response in cutaneous metastases across different cancer types.

METHODS

Patients with tumours ≤3 cm of any histology were included (stable or progressing on current therapy ≥2 months), at three centres. Tumours were treated with 220 mM calcium chloride injection and manual application of eight 0.1 ms pulses with 1 kV/cm and 1Hz with a handheld electrode, in local or general anaesthesia. Clinical response was evaluated after 1, 2, 3, 4, 5, 6, and 12 months. Primary endpoint was response at two months. The overall response rate (ORR) was partial- and complete responses of treated tumours. MR-imaging and qualitative interviews were performed in respective subsets.

RESULTS

Nineteen patients with disseminated cancer (breast n = 4, lung n = 5, pancreatic n = 1, colorectal n = 2, gastric n = 1, and endometrial cancer n = 1) were enrolled, and 58 metastases were treated (50 once, 8 retreated). The ORR was 36% (95% CI 22-53) after two months. Best ORR was 51% (CR 42%; PR 9%). Previous irradiation improved outcomes (p = 0.0004). Adverse events were minimal. Median pain score was reduced after two months (p = 0.017). Treatment may relieve symptoms according to qualitative interviews. MRI showed restriction in treated tissue.

CONCLUSION

The majority of tumours were treated only once with calcium electroporation, achieving an ORR of 36% after two months and best ORR of 51%. Efficacy, symptom-relief and safety support calcium electroporation as a palliative treatment option for cutaneous metastases.

Pulsed Electric Fields in Oncology: A Snapshot of Current Clinical Practices and Research Directions from the 4th World Congress of Electroporation

The 4th World Congress of Electroporation (Copenhagen, 9-13 October 2022) provided a unique opportunity to convene leading experts in pulsed electric fields (PEF). PEF-based therapies harness electric fields to produce therapeutically useful effects on cancers and represent a valuable option for a variety of patients. As such, irreversible electroporation (IRE), gene electrotransfer (GET), electrochemotherapy (ECT), calcium electroporation (Ca-EP), and tumour-treating fields (TTF) are on the rise. Still, their full therapeutic potential remains underappreciated, and the field faces fragmentation, as shown by parallel maturation and differences in the stages of development and regulatory approval worldwide. This narrative review provides a glimpse of PEF-based techniques, including key mechanisms, clinical indications, and advances in therapy; finally, it offers insights into current research directions. By highlighting a common ground, the authors aim to break silos, strengthen cross-functional collaboration, and pave the way to novel possibilities for intervention. Intriguingly, beyond their peculiar mechanism of action, PEF-based therapies share technical interconnections and multifaceted biological effects (e.g., vascular, immunological) worth exploiting in combinatorial strategies.

Evaluation of the Anticancer Activity of Calcium Ions Introduced into Human Breast Adenocarcinoma Cells MCF-7/WT and MCF-7/DOX by Electroporation

Breast cancer ranks among the top three most common malignant neoplasms in Poland. The use of calcium ion-assisted electroporation is an alternative approach to the classic treatment of this disease. The studies conducted in recent years confirm the effectiveness of electroporation with calcium ions. Electroporation is a method that uses short electrical pulses to create transitional pores in the cell membrane to allow the penetration of certain drugs. The aim of this study was to investigate the antitumor effects of electroporation alone and calcium ion-assisted electroporation on human mammary adenocarcinoma cells that are sensitive (MCF-7/WT) and resistant to doxorubicin (MCF-7/DOX). The cell viability was assessed using independent tests: MTT and SRB. The type of cell death after the applied therapy was determined by TUNEL and flow cytometry (FACS) methods. The expression of Cav3.1 and Cav3.2 proteins of T-type voltage-gated calcium channels was assessed by immunocytochemistry, and changes in the morphology of CaEP-treated cells were visualized using a holotomographic microscope. The obtained results confirmed the effectiveness of the investigated therapeutic method. The results of the work constitute a good basis for planning research at the in vivo level and in the future to develop a more effective and safer method of breast cancer treatment for patients.

The effectiveness of calcium electroporation combined with gene electrotransfer of a plasmid encoding IL-12 is tumor type-dependent

Introduction

In calcium electroporation (CaEP), electroporation enables the cellular uptake of supraphysiological concentrations of Ca2+, causing the induction of cell death. The effectiveness of CaEP has already been evaluated in clinical trials; however, confirmatory preclinical studies are still needed to further elucidate its effectiveness and underlying mechanisms. Here, we tested and compared its efficiency on two different tumor models to electrochemotherapy (ECT) and in combination with gene electrotransfer (GET) of a plasmid encoding interleukin-12 (IL-12). We hypothesized that IL-12 potentiates the antitumor effect of local ablative therapies as CaEP and ECT.

Methods

The effect of CaEP was tested in vitro as well as in vivo in murine melanoma B16-F10 and murine mammary carcinoma 4T1 in comparison to ECT with bleomycin. Specifically, the treatment efficacy of CaEP with increasing calcium concentrations alone or in combination with IL-12 GET in different treatment protocols was investigated. We closely examined the tumor microenvironment by immunofluorescence staining of immune cells, as well as blood vessels and proliferating cells.

Results

In vitro, CaEP and ECT with bleomycin reduced cell viability in a dose-dependent manner. We observed no differences in sensitivity between the two cell lines. A dose-dependent response was also observed in vivo; however, the efficacy was better in 4T1 tumors than in B16-F10 tumors. In 4T1 tumors, CaEP with 250 mM Ca resulted in more than 30 days of growth delay, which was comparable to ECT with bleomycin. In contrast, adjuvant peritumoral application of IL-12 GET after CaEP prolonged the survival of B16-F10, but not 4T1-bearing mice. Moreover, CaEP with peritumoral IL-12 GET modified tumor immune cell populations and tumor vasculature.

Conclusions

Mice bearing 4T1 tumors responded better to CaEP in vivo than mice bearing B16-F10 tumors, even though a similar response was observed in vitro. Namely, one of the most important factors might be involvement of the immune system. This was confirmed by the combination of CaEP or ECT with IL-12 GET, which further enhanced antitumor effectiveness. However, the potentiation of CaEP effectiveness was also highly dependent on tumor type; it was more pronounced in poorly immunogenic B16-F10 tumors compared to moderately immunogenic 4T1 tumors.

Investigation of imbalances in essential/toxic metal levels in the blood of laryngeal cancer patients in comparison with controls

Laryngeal carcinoma is one of the common types of head and neck cancer, with men being more likely than women to develop it. Diet, age, gender, smoking habits, and environmental factors play important roles in its development. The goal of this study was to ascertain if there were imbalances in essential and toxic trace metals owing to the initiation and progression of laryngeal cancer. Atomic absorption spectrometry was employed to quantify selected macroelements, and essential/toxic trace metals in blood of the cancerous patients and matching controls. Significantly higher concentrations of Pb, Cu, Fe, and Sr while substantially lower levels of Na, K, Ca, and Mg were observed in the cancer patients compared with the controls. Considerably disparate mutual relationships among the macroelements, and essential/toxic trace metals in the patients and controls were manifested by their correlation coefficients. Similarly, multivariate apportionment of the metal levels showed appreciably diverse associations and grouping in the patients and controls. The laryngeal cancer patients exhibited significant disparities in the metal levels among various sub-types (supraglottic, subglottic, transglottic, and glottic cancer) and stages (I, II, III, and IV) of the disease. Most of the metals revealed distinct differences based on the gender, habitat, age, eating preferences, and smoking habits in both donor groups. Overall, the study demonstrated significant imbalances among the macroelements, and essential/toxic trace metal levels in the blood of laryngeal cancer patients compared to the controls.

Molecular and Functional Characterization of BDNF-Overexpressing Human Retinal Pigment Epithelial Cells Established by Sleeping Beauty Transposon-Mediated Gene Transfer

More and more patients suffer from multifactorial neurodegenerative diseases, such as age-related macular degeneration (AMD). However, their pathological mechanisms are still poorly understood, which complicates the development of effective therapies. To improve treatment of multifactorial diseases, cell-based gene therapy can be used to increase the expression of therapeutic factors. To date, there is no approved therapy for dry AMD, including late-stage geographic atrophy. We present a treatment option for dry AMD that transfers the brain-derived neurotrophic factor (BDNF) gene into retinal pigment epithelial (RPE) cells by electroporation using the plasmid-based Sleeping Beauty (SB) transposon system. ARPE-19 cells and primary human RPE cells were co-transfected with two plasmids encoding the SB100X transposase and the transposon carrying a BDNF transcription cassette. We demonstrated efficient expression and secretion of BDNF in both RPE cell types, which were further increased in ARPE-19 cell cultures exposed to hydrogen peroxide. BDNF-transfected cells exhibited lower apoptosis rates and stimulated neurite outgrowth in human SH-SY5Y cells. This study is an important step in the development of a cell-based BDNF gene therapy that could be applied as an advanced therapy medicinal product to treat dry AMD or other degenerative retinal diseases.

Early Single-Center Experience With Irreversible Electroporation for Stage 2, 3, and 4 Pancreatic Adenocarcinomas

OBJECTIVES

Irreversible electroporation (IRE) is an ablation technology that uses electrical energy delivered between electrodes. If the electrodes are placed atraumatically, there is little to no risk of collateral injury, making IRE appealing for the treatment of pancreatic tumors.

METHODS

We report on 20 patients with pancreatic adenocarcinoma (PAC) who underwent 21 IRE in our center. There were 6 IRE for stage 2 PAC, 11 for stage 3 PAC, 1 for stage 4 PAC, and 2 patients treated with IRE for recurrence after pancreaticoduodenectomy. One patient had local progression 18 months after IRE and received a second IRE treatment. Using propensity score matching (age, sex, stage, tumor size, and chemotherapy), cases were matched 2 to 1 with patients from the Surveillance, Epidemiology, and End Results database.

RESULTS

A total of 7 cases experienced 8 complications; 4 complications were mild, and 4 were severe. Significant survival benefit was seen for patients with stage 3 PAC (27.5 vs 14.6 months for the matched group, P = 0.003); for stage 2, median survival was 15 months, and the single stage 4 patient survived 9 months after IRE treatment.

CONCLUSIONS

Pancreatic cancers were safely and effectively treated with image-guided IRE in our medium-sized center.

Integrated platform for culture, observation, and parallelized electroporation of spheroids

Reversible electroporation is a method to introduce molecules into cells by increasing the permeability of their membranes, thanks to the application of pulsed electric fields. One of its main biomedical applications is electro-chemotherapy, where electroporation is used to deliver anticancer drugs into tumor tissues. To improve our understanding of the electroporation effect on tissues and select efficient treatments, in vitro tumor models are needed. Cell spheroids are relevant models as they can reproduce tumor microenvironment and cell-cell interactions better than 2D cell cultures. Various methods offering a relatively simple workflow are now available for their production. However, electroporation protocols usually require handling steps that may damage spheroids and result in random spacing, inducing variations in electric field distribution around spheroids and non-reproducible electroporation conditions. In addition, only a few microsystems allow the production and electroporation of spheroids, and the spheroids produced lack reproducibility in size and location. To overcome these issues, we developed a unique device enabling culture, monitoring, and electroporation of hundreds of regular spheroids in parallel, with a design ensuring that all spheroids are submitted to the same electric field conditions. It is comprised of a microfluidic chamber encompassing a micro-structured agarose gel, allowing easy medium exchange while avoiding spheroid handling. It also enables optical imaging of spheroids in situ, thanks to transparent electrodes. In this paper, we describe the fabrication and characterization of the developed microsystem and demonstrate its applicability to electroporation of a network of spheroids. We present a first successful application as an anticancer drug testing platform, by evaluating the bleomycin effect on HT29 colorectal cancer cell spheroids. This work opens new perspectives in the development of in vitro assays for the preclinical evaluation of electroporation-based treatment.

Calcium Electroporation Reduces Viability and Proliferation Capacity of Four Uveal Melanoma Cell Lines in 2D and 3D Cultures

Simple Summary

Calcium electroporation (CaEP) is an innovative anti-tumor treatment modality that induces cell death by introducing supraphysiological concentrations of calcium into cells with a limited effect on normal cells. The objective of the present study is to assess the effect of CaEP in uveal melanoma (UM) cell lines in comparison to electrochemotherapy (ECT) with bleomycin using 2D monolayer cell cultures as well as 3D tumor spheroid models in four different UM cell lines. The morphological changes of the spheroids, the cell viability, growth rate as well as the cytotoxic effect of electroporation (EP) with calcium chloride and bleomycin were evaluated with various drug concentrations. The results of CaEP and ECT both suggest a comparable dose-dependent reduction in cell viability and proliferation rate in all tested 2D cell lines and 3D tumor spheroids. These data point out that CaEP is an established anticancer treatment causing cell death by ATP depletion in in vitro and in vivo, representing an efficient alternative therapy with a lower cytotoxic potency for the local UM tumor control.

Abstract

Electrochemotherapy (ECT) is the combination of transient pore formation following electric pulse application with the administration of cytotoxic drugs, which enhances the cytotoxic effect of the applied agent due to membrane changes and permeabilization. Although EP represents an established therapeutic option for solid malignancies, recent advances shift to the investigation of non-cytotoxic agents, such as calcium, which can also induce cell death. The present study aims to evaluate the cytotoxic effect, the morphological changes in tumor spheroids, the effect on the cell viability, and the cell-specific growth rate following calcium electroporation (CaEP) in uveal melanoma (UM) 2D monolayer cell cultures as well as in 3D tumor spheroid models. The experiments were conducted in four cell lines, UM92.1, Mel270, and two primary UM cell lines, UPMD2 and UPMM3 (UPM). The 2D and 3D UM cell cultures were electroporated with eight rectangular pulses (100 µs pulse duration, 5 Hz repetition frequency) of a 1000 V/cm pulse strength alone or in combination with 0.11 mg/mL, 0.28 mg/mL, 0.55 mg/mL or 1.11 mg/mL calcium chloride or 1.0 µg/mL or 2.5 µg/mL bleomycin. The application of calcium chloride alone induced an ATP reduction only in the UM92.1 2D cell cultures. Calcium alone had no significant effect on ATP levels in all four UM spheroids. A significant decrease in the intracellular adenosine triphosphate (ATP) level was documented in all four 2D and 3D cell cultures for both CaEP as well as ECT with bleomycin. The results suggest a dose-dependent ATP depletion with a wide range of sensitivity among the tested UM cell lines, control groups, and the applied settings in both 2D monolayer cell cultures and 3D tumor spheroid models. The colony formation capacity of the cell lines after two weeks reduced significantly after CaEP only with 0.5 mg/mL and 1.1 mg/mL, whereas the same effect could be achieved with both applied bleomycin concentrations, 1.0 µg/mL and 2.5 µg/mL, for the ECT group. The specific growth rate on day 7 following CaEP was significantly reduced in UM92.1 cell lines with 0.5 and 1.1 mg/mL calcium chloride, while Mel270 showed a similar effect only after administration of 1.1 mg/mL. UM92.1 and Mel270 spheroids exhibited lower adhesion and density after CaEP on day three in comparison to UPM spheroids showing detachment after day 7 following treatment. CaEP and bleomycin electroporation significantly reduce cell viability at similar applied voltage settings. CaEP may be a feasible and inexpensive therapeutic option for the local tumor control with fewer side effects, in comparison to other chemotherapeutic agents, for the treatment of uveal melanoma. The limited effect on normal cells and the surrounding tissue has already been investigated, but further research is necessary to clarify the effect on the surrounding tissue and to facilitate its application in a clinical setting for the eye.

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.

Study protocol designed to investigate tumour response to calcium electroporation in cancers affecting the skin: a non-randomised phase II clinical trial

INTRODUCTION

Skin malignancy is a distressing problem for many patients, and clinical management is challenging. This article describes the protocol for the Calcium Electroporation Response Study (CaEP-R) designed to investigate tumour response to calcium electroporation and is a descriptive guide to calcium electroporation treatment of malignant tumours in the skin. Calcium electroporation is a local treatment that induces supraphysiological intracellular calcium levels by intratumoural calcium administration and application of electrical pulses. The pulses create transient membrane pores allowing diffusion of non-permeant calcium ions into target cells. High calcium levels can kill cancer cells, while normal cells can restore homeostasis. Prior trials with smaller cohorts have found calcium electroporation to be safe and efficient. This trial aims to include a larger multiregional cohort of patients with different cancer diagnoses and also to investigate treatment areas using MRI as well as assess impact on quality of life.

METHODS AND ANALYSIS

This non-randomised phase II multicentre study will investigate response to calcium electroporation in 30 patients with cutaneous or subcutaneous malignancy. Enrolment of 10 patients is planned at three centres: Zealand University Hospital, University Hospital of Southern Denmark and University Hospital Schleswig-Holstein. Response after 2 months was chosen as the primary endpoint based on short-term response rates observed in a prior clinical study. Secondary endpoints include response to treatment using MRI and change in quality of life assessed by questionnaires and qualitative interviews.

ETHICS AND DISSEMINATION

The trial is approved by the Danish Medicines Agency and The Danish Regional Committee on Health Research Ethics. All included patients will receive active treatment (calcium electroporation). Patients can continue systemic treatment during the study, and side effects are expected to be limited. Data will be published in a peer-reviewed journal and made available to the public.

TRIAL REGISTRATION NUMBERS

NCT04225767 and EudraCT no: 2019-004314-34.

Cell death due to electroporation - A review

Exposure of cells to high voltage electric pulses increases transiently membrane permeability through membrane electroporation. Electroporation can be reversible and is used in gene transfer and enhanced drug delivery but can also lead to cell death. Electroporation resulting in cell death (termed as irreversible electroporation) has been successfully used as a new non-thermal ablation method of soft tissue such as tumours or arrhythmogenic heart tissue. Even though the mechanisms of cell death can influence the outcome of electroporation-based treatments due to use of different electric pulse parameters and conditions, these are not elucidated yet. We review the mechanisms of cell death after electroporation reported in literature, cell injuries that may lead to cell death after electroporation and membrane repair mechanisms involved. The knowledge of membrane repair and cell death mechanisms after cell exposure to electric pulses, targets of electric field in cells need to be identified to optimize existing and develop of new electroporation-based techniques used in medicine, biotechnology, and food technology.

Molecular dynamics simulations of the effects of lipid oxidation on the permeability of cell membranes

The formation of transient pores in their membranes is a well-known mechanism of permeabilization of cells exposed to high-intensity electric pulses. However, the formation of such pores is not able to explain all aspects of the so-called electroporation phenomenon. In particular, the reasons for sustained permeability of cell membranes, persisting long after the pulses' application, remain elusive. The complete resealing of cell membranes takes indeed orders of magnitude longer than the time for electropore closure as reported from molecular dynamics (MD) investigations. Lipid peroxidation has been suggested as a possible mechanism to explain the sustainable permeability of cell membranes. However, theoretical investigations of membrane lesions containing excess amounts of hydroperoxides have shown that the conductivities of such lesions were not high enough to account for the experimental measurements. Here, expanding on these studies, we investigate quantitatively the permeability of cell membrane lesions that underwent secondary oxidation. MD simulations and free energy calculations of lipid bilayers show that such lesions provide a better model of post-pulse permeable and conductive electropermeabilized cells. These results are further discussed in the context of sonoporation and ferroptosis, respectively a procedure and a phenomenon, among others, in which, alike electroporation, substantial lipid oxidation might be triggered.

PARP inhibitor olaparib has a potential to increase the effectiveness of electrochemotherapy in BRCA1 mutated breast cancer in mice

Electrochemotherapy (ECT), a local therapy, has different effectiveness among tumor types. In breast cancer, its effectiveness is low; therefore, combined therapies are needed. The aim of our study was to combine ECT with PARP inhibitor olaparib, which could inhibit the repair of bleomycin or cisplatin induced DNA damage and potentiate the effectiveness of ECT. The effects of combined therapy were studied in BRCA1 mutated (HCC1937) and non-mutated (HCC1143) triple negative breast cancer cell lines. Therapeutic effectiveness was studied in 2D and 3D cell cultures and in vivo on subcutaneous HCC1937 tumor model in mice. The underlying mechanism of combined therapy was determined with the evaluation of γH2AX foci. Combined therapy of ECT with bleomycin and olaparib potentiated the effectiveness of ECT in BRCA1 mutated HCC1937, but not in non-mutated HCC1143 cells. The combined therapy had a synergistic effect, which was due to the increased number of DNA double strand breaks. Addition of olaparib to ECT with bleomycin in vivo in HCC1937 tumor model had only minimal effect, indicating repetitive olaparib treatment would be needed. This study demonstrates that DNA repair inhibiting drugs, like olaparib, have the potential to increase the effectiveness of ECT with bleomycin.

The electrical pulse application enhances intra-cellular localization and potentiates cytotoxicity of curcumin in breast cancer cells

Breast cancer is the most common cancer of women, and fifth leading cause of mortality worldwide. Existing breast cancer regimens are costly and produce severe side effects. This highlights a need for the development of efficient novel therapies, which are cost effective and limit side effects. An electrical pulse (EP)-based chemo therapy, known as electrochemotherapy (ECT) using the natural compound curcumin could be an effective alternative. ECT is a non-surgical modality, which produces excellent anti-tumor efficacy at small drug concentrations due to increased uptake of drugs. In clinics, ECT is shown to be effective in treating advanced, recurrent, and metastatic breast cancers, which are refractory to multiple modalities. ECT with curcumin triggers apoptotic cell death in breast cancer cells and could be an effective alternative, due to curcumin's low cost and reduced side-effects. However, there is a lack of studies quantifying the uptake of curcumin in response to EP application. Towards this, we determined the uptake of different curcuminoids (curcumin, desmethoxycurcumin, and bisdemethoxycurcumin) upon EP application and their impact on cell cytotoxicity. Additionally, we studied the combined effect of calcium chloride (CaCl₂) and a curcuminoids (Cur) mixture, based on initial studies suggesting calcium electroporation as a potential inexpensive anti-cancer treatment. Our results indicate EP with Cur increases cellular uptake, cell shrinkage, and cytotoxicity. The EP + Cur resulted in the highest uptake of the bisdemethoxycurcumin. Further, EP also potentiated the cytotoxicity of CaCl₂ and of the Cur and CaCl₂ combination against breast cancer cells and caused apoptosis. Our preliminary data pave the way to further studies on Cur and CaCl₂ combination treating breast cancer.

In Vitro Study of Calcium Microsecond Electroporation of Prostate Adenocarcinoma Cells

Electroporation, applied as a non-thermal ablation method has proven to be effective for focal prostate treatment. In this study, we performed pre-clinical research, which aims at exploring the specific impact of this so-called calcium electroporation on prostate cancer. First, in an in-vitro study of DU 145 cell lines, microsecond electroporation (μsEP) parameters were optimized. We determined hence the voltage that provides both high permeability and viability of these prostate cancer cells. Subsequently, we compared the effect of μsEP on cells' viability with and without calcium administration. For high-voltage pulses, the cell death's mechanism was evaluated using flow-cytometry and confocal laser microscopy. For lower-voltage pulses, the influence of electroporation on prostate cancer cell mobility was studied using scratch assays. Additionally, we applied calcium-binding fluorescence dye (Fluo-8) to observe the calcium uptake dynamic with the fluorescence microscopy. Moreover, the molecular dynamics simulation visualized the process of calcium ions inflow during μsEP. According to our results calcium electroporation significantly decreases the cells viability by promoting apoptosis. Furthermore, our data shows that the application of pulsed electric fields disassembles the actin cytoskeleton and influences the prostate cancer cells' mobility.

Energy Metabolism Decline in the Aging Brain-Pathogenesis of Neurodegenerative Disorders

There is a growing body of evidencethat indicates that the aging of the brain results from the decline of energy metabolism. In particular, the neuronal metabolism of glucose declines steadily, resulting in a growing deficit of adenosine triphosphate (ATP) production-which, in turn, limits glucose access. This vicious circle of energy metabolism at the cellular level is evoked by a rising deficiency of nicotinamide adenine dinucleotide (NAD) in the mitochondrial salvage pathway and subsequent impairment of the Krebs cycle. A decreasing NAD level also impoverishes the activity of NAD-dependent enzymes that augments genetic errors and initiate processes of neuronal degeneration and death.This sequence of events is characteristic of several brain structures in which neurons have the highest energy metabolism. Neurons of the cerebral cortex and basal ganglia with long unmyelinated axons and these with numerous synaptic junctions are particularly prone to senescence and neurodegeneration. Unfortunately, functional deficits of neurodegeneration are initially well-compensated, therefore, clinical symptoms are recognized too late when the damages to the brain structures are already irreversible. Therefore, future treatment strategies in neurodegenerative disorders should focus on energy metabolism and compensation age-related NAD deficit in neurons. This review summarizes the complex interrelationships between metabolic processes on the systemic and cellular levels and provides directions on how to reduce the risk of neurodegeneration and protect the elderly against neurodegenerative diseases.

Starting a Fire Without Flame: The Induction of Cell Death and Inflammation in Electroporation-Based Tumor Ablation Strategies

New therapeutic strategies and paradigms are direly needed for the treatment of cancer. While the surgical removal of tumors is favored in most cancer treatment plans, resection options are often limited based on tumor localization. Over the last two decades, multiple tumor ablation strategies have emerged as promising stand-alone or combination therapeutic options for patients. These strategies are often employed to treat tumors in areas where surgical resection is not possible or where chemotherapeutics have proven ineffective. The type of cell death induced by the ablation modality is a critical aspect of therapeutic success that can impact the efficacy of the treatment and systemic anti-tumor immune system responses. Electroporation-based ablation technologies include electrochemotherapy, irreversible electroporation, and other modalities that rely on pulsed electric fields to create pores in cell membranes. These pores can either be reversible or irreversible depending on the electric field parameters and can induce cell death either alone or in combination with a therapeutic agent. However, there have been many controversial findings among these technologies as to the cell death type initiated, from apoptosis to pyroptosis. As cell death mechanisms can impact treatment side effects and efficacy, we review the main types of cell death induced by electroporation-based treatments and summarize the impact of these mechanisms on treatment response. We also discuss potential reasons behind the variability of findings such as the similarities between cell death pathways, differences between cell-types, and the variation in electric field strength across the treatment area.

Calcium Electroporation of Equine Sarcoids

Sarcoids are common equine skin tumors where the risk of recurrence after treatment is high, and better treatment options are warranted. Calcium electroporation is a novel anti-cancer treatment where lethally high calcium concentrations are introduced into the cells by electroporation, a method where short high-voltage pulses induce transient permeabilization of the cell membrane. This study investigated the safety and long-term response of calcium electroporation on sarcoids. Thirty-two sarcoids in eight horses were included. The study suggested that calcium electroporation is a safe and feasible treatment for sarcoids, including inoperable sarcoids. Horses were treated once (2/8) or twice (6/8) under general anesthesia, where sarcoids were injected with 220 mM calcium chloride followed by electroporation with 8 pulses of 100 μs, 1 kV/cm, and 1 Hz. Biopsies were taken prior to treatment. The sarcoid size was monitored for 12-38 weeks after the first treatment. Complete response was observed in 22% (6/27) of treated sarcoids, and partial response in 22% (6/27), giving a 44% total response. Treatment efficacy did not appear to be related to location, type, or size. In all non-biopsied lesions, a complete response was seen (4/4). In conclusion, in this small study, 44% of sarcoids responded with 22% of sarcoids disappearing.