Antitumor effectiveness of electrochemotherapy: a systematic review and meta-analysis. Eur J Surg Oncol. 2013;39:4-16. [PMID: 22980492 DOI: 10.1016/j.ejso.2012.08.016]

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.

The additive effect of 17β-estradiol on the modulation of electrochemotherapy with calcium ions or cisplatin in human clear carcinoma cells

Calcium electroporation (CaEP) is an efficient approach for ovarian cancer treatment. It causes cell death by introducing elevated levels of calcium into cells. In this work, the research focused on two types of cell lines: CHO-K1, representing normal ovary cells, and OvBH-1, representing ovarian clear carcinoma cells. Those cell lines exhibited distinct reactions to calcium electroporation (CaEP). Also, we have evaluated the effects of 17β-estradiol following CaEP and electrochemotherapy (ECT) with cisplatin (CPP). The combination of ECT with CPP and CaEP with prior E2 preincubation resulted in approximately 23.55 % and 39 % decreases in cell survival compared to the control cells (exposed to CPP and CaCl2 alone) for ovarian cancer cells. The obtained results showed that ovarian cancer cells preincubated with 17β-estradiol after exposure to pulsed electric fields undergo primary necrosis. Additionally, preincubation of ovarian cancer cells with 17β-estradiol can significantly improve the effectiveness of both chemotherapy and electrochemotherapy involving cisplatin and calcium chloride.

Treatment benefit of electrochemotherapy for superficial squamous cell carcinoma: a systematic review and single-arm meta-analysis

OBJECTIVE

Treating aggressive superficial squamous cell carcinoma (SCC) poses challenges due to invasiveness. Palliative care is recommended for inoperable cases with extensive tumors near vital organs, risking disfigurement or functional impairment. Electrochemotherapy (ECT) is an emerging cutaneous tumor treatment, but its efficacy against superficial SCC remains uncertain. This study conducts a systematic review and single-arm meta-analysis to evaluate ECT's effectiveness against superficial SCC and provide current evidence for clinical practice.

METHODS

Embase, PubMed and Cochrane Library were searched for studies up to May 2023. The random effects model analyzed complete response (CR) and partial response (PR), with subgroup assessment based on drug dosage, treatment response evaluation, tumor size, primary/recurrent status, and tumor location.

RESULTS

Ten studies involving 162 patients and 208 tumors were included. Pooled CR and PR rates for ECT-treated superficial SCC were 66.5% (95% CI 48.4%-82.5%; I2 = 84%) and 20.3% (95% CI 10.5%-32.3%; I2 = 70%), respectively. Subgroup analysis indicated ECT's superiority in treating primary tumors (PR: 70%, CR: 30%) and tumors ≤ 3 cm (PR: 81.3%, CR: 10.1%) compared to recurrent tumors (PR: 56.7%, CR: 36.5%) and tumors > 3 cm (PR: 45.2%, CR: 34.4%).

CONCLUSION

This single-arm meta-analysis confirms ECT's efficacy against superficial SCC, especially in primary tumors and those ≤ 3 cm in diameter. The study highlights the impact of tumor location and response evaluation on ECT's benefits, warranting further investigation through additional research.

Electroporation in Cancer Therapy: A Simplified Model Derived from the Hodgkin-Huxley Model

Cancer remains a global health challenge, necessitating effective treatments with fewer side effects. Traditional methods such as chemotherapy and surgery often have complications. Pulsed electric fields and electroporation have emerged as promising approaches to mitigate these challenges. This study presents a comprehensive overview of electroporation as an innovative tool in cancer therapy, encompassing critical elements such as pulse generators and delivery devices. Furthermore, it introduces a simplified reversible electroporation model grounded in the Hodgkin-Huxley model. This model ensures resting potential stability by regulating ionic currents. When membrane charges reach the electroporation threshold, the model swiftly increases the fraction of open pores, resulting in a rapid rise in electroporation current. Conversely, as the transmembrane potential drops below the threshold, the model gradually reduces the fraction of open pores, leading to a gradual decline in electroporation current, indicating pore resealing. This model contributes to easier modeling and implementation of reversible electroporation dynamics, providing a valuable tool for further exploration of electroporation for cancer therapy.

Characterizing parameters and incorporating action potentials via the Hodgkin-Huxley model in a novel electric model for living cells

To enhance our understanding of electroporation and optimize the pulses used within the frequency range of 1 kHz to 100 MHz, with the aim of minimizing side effects such as muscle contraction, we introduce a novel electrical model, structured as a 2D representation employing exclusively lumped elements. This model adeptly encapsulates the intricate dynamics of living cells' impedance variation. A distinguishing attribute of the proposed model lies in its capacity to decipher the distribution of transmembrane potential across various orientations within living cells. This aspect bears critical importance, particularly in contexts such as electroporation and cellular stimulation, where precise knowledge of potential gradients is pivotal. Furthermore, the augmentation of the proposed electrical model with the Hodgkin-Huxley (HH) model introduces an additional dimension. This integration augments the model's capabilities, specifically enabling the exploration of muscle cell stimulation and the generation of action potentials. This broader scope enhances the model's utility, facilitating comprehensive investigations into intricate cellular behaviors under the influence of external electric fields.

The Long-Term Results of Electrochemotherapy in the Treatment of Patients with Locoregionally Advanced, Unresectable Melanoma

Background/Objectives: Despite observing progress in recent years in the treatment of patients with advanced melanoma, the optimal management of locoregional recurrence has not been determined. Various methods are used to treat this group of patients. One of these methods is electrochemotherapy. The present study presents the distant results in treating patients with the locoregional recurrence of melanoma, using the technique of electrochemotherapy. Methods: This study includes a retrospective analysis of 88 patients' data with locoregional melanoma recurrence, treated with electrochemotherapy (ECT) between 2010 and 2023, in two reference centers. Results: Approximately 80% of patients responded to the ECT treatment, achieving partial or complete remission. In a multivariate analysis, statistically significant longer overall survival was found in the group of patients who achieved complete remission after ECT and were treated with immunotherapy. Discussion: The results may suggest the existence of synergy between ECT and immunotherapy. However, confirmation of this fact requires further prospective studies that will also establish the role of ECT in the combination treatment of patients with locoregional recurrence of melanoma.

An experimental and theoretical study on cell swelling for osmotic imbalance induced by electroporation

The cellular membrane serves as a pivotal barrier in regulating intra- and extracellular matter exchange. Disruption of this barrier through pulsed electric fields (PEFs) induces the transmembrane transport of ions and molecules, creating a concentration gradient that subsequently results in the imbalance of cellular osmolality. In this study, a multiphysics model was developed to simulate the electromechanical response of cells exposed to microsecond pulsed electric fields (μsPEFs). Within the proposed model, the diffusion coefficient of the cellular membrane for various ions was adjusted based on electropore density. Cellular osmolality was governed and described using Van't Hoff theory, subsequently converted to loop stress to dynamically represent the cell swelling process. Validation of the model was conducted through a hypotonic experiment and simulation at 200 mOsm/kg, revealing a 14.2% increase in the cell's equivalent radius, thereby confirming the feasibility of the cell mechanical model. With the transmembrane transport of ions induced by the applied μsPEF, the hoop stress acting on the cellular membrane reached 179.95 Pa, and the cell equivalent radius increased by 11.0% when the extra-cellular medium was supplied with normal saline. The multiphysics model established in this study accurately predicts the dynamic changes in cell volume resulting from osmotic imbalance induced by PEF action. This model holds theoretical significance, offering valuable references for research on drug delivery and tumor microenvironment modulation.

Electrochemotherapy in Kaposi's Sarcoma Patients: From the Gold Standard Strategy to Locally Advanced Cutaneous and Subcutaneous Lesions

Electrochemotherapy (ECT) is one of the newest therapeutic strategies employed as a medical procedure for skin neoplasms' treatment, especially for classic Kaposi's sarcoma (CKS). The aim of this study was to demonstrate ECT clinical response and the local control of CKS disease. The primary endpoint was to value the worth and efficacy of this local therapy in CKS skin lesions' treatment. In total, 19 CKS patients were enrolled, 14 males and 5 females with median age at diagnosis of 72. Complete response (CR) has been gained in 12 patients after first ECT attempt; meanwhile, 3 and 4 out of 19 patients obtained a partial response (PR), so they underwent a second and third ECT treatment, respectively. Clinical response was evaluated during the entire timeframe of the follow-up, which ranged between 3 months and 4 years with a median of 18 months. The control of CKS skin lesions still represents a challenge for surgeons and oncologists. Nevertheless, according to this and other authors' recent experiences, ECT could be considered the gold standard strategy for early-stage patients, but at the same time it could be considered as a valid option in controlling Kaposi's sarcoma locally advanced lesions.

Electroporation in Translational Medicine: From Veterinary Experience to Human Oncology

Electroporation (EP) is a broadly accepted procedure that, through the application of electric pulses with appropriate amplitudes and waveforms, promotes the delivery of anticancer molecules in various oncology therapies. EP considerably boosts the absorptivity of targeted cells to anticancer molecules of different natures, thus upgrading their effectiveness. Its use in veterinary oncology has been widely explored, and some applications, such as electrochemotherapy (ECT), are currently approved as first-line treatments for several neoplastic conditions. Other applications include irreversible electroporation and EP-based cancer vaccines. In human oncology, EP is still mostly restricted to therapies for cutaneous tumors and the palliation of cutaneous and visceral metastases of malignant tumors. Fields where veterinary experience could help smooth the clinical transition to humans include intraoperative EP, interventional medicine and cancer vaccines. This article recapitulates the state of the art of EP in veterinary and human oncology, recounting the most relevant results to date.

Bilayer Charge Asymmetry and Oil Residues Destabilize Membranes upon Poration

Transmembrane asymmetry is ubiquitous in cells, particularly with respect to lipids, where charged lipids are mainly restricted to one monolayer. We investigate the influence of anionic lipid asymmetry on the stability of giant unilamellar vesicles (GUVs), minimal plasma membrane models. To quantify asymmetry, we apply the fluorescence quenching assay, which is often difficult to reproduce, and caution in handling the quencher is generally underestimated. We first optimize this assay and then apply it to GUVs prepared with the inverted emulsion transfer protocol by using increasing fractions of anionic lipids restricted to one leaflet. This protocol is found to produce highly asymmetric bilayers but with ∼20% interleaflet mixing. To probe the stability of asymmetric versus symmetric membranes, we expose the GUVs to porating electric pulses and monitor the fraction of destabilized vesicles. The pulses open macropores, and the GUVs either completely recover or exhibit leakage or bursting/collapse. Residual oil destabilizes porated membranes, and destabilization is even more pronounced in asymmetrically charged membranes. This is corroborated by the measured pore edge tension, which is also found to decrease with increasing charge asymmetry. Using GUVs with imposed transmembrane pH asymmetry, we confirm that poration-triggered destabilization does not depend on the approach used to generate membrane asymmetry.

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.

Calcium electroporation causes ATP depletion in cells and is effective both in microsecond and nanosecond pulse range as a modality of electrochemotherapy

Calcium electroporation is a modality of electrochemotherapy (ECT), which is based on intracellular electric field-mediated delivery of cytotoxic doses of calcium into the cells resulting in rapid cell death. In this work, we have developed a CHO-K1 luminescent cell line, which allowed the estimation of cell membrane permeabilization, ATP depletion and cytotoxicity evaluation without the use of additional markers and methodologies. We have shown the high efficiency of nanosecond pulses compressed into a MHz burst for application in calcium ECT treatments. The 5 kV/cm and 10 kV/cm nanosecond (100 and 600 ns) pulses were delivered in bursts of 10, 50 and 100 pulses (a total of 12 parametric protocols) and then compared to standard microsecond range sequences (100 µs × 8) of 0.4-1.4 kV/cm. The effects of calcium-free, 2 mM and 5 mM calcium electroporation treatments were characterized. It was shown that reversible electroporation is accompanied by ATP depletion associated with membrane damage, while during calcium ECT the ATP depletion is several-fold higher, which results in cell death. Finally, efficacy-wise equivalent pulse parameters from nanosecond and microsecond ranges were established, which can be used for calcium nano-ECT as a better alternative to ESOPE (European Standard Operating Procedures on Electrochemotherapy) protocols.

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.

Effectiveness and tolerance of electrochemotherapy as palliative therapy for patients with head and neck cancer and malignant melanoma and its relation to early skin reaction

OBJECTIVES

To evaluate the efficacy and tolerance after the electrochemotherapy treatment for local therapy of cutaneous and subcutaneous metastases of head-and-neck tumors and malignant melanoma refractory to standard therapies, mainly in neck metastasis of squamous cell carcinoma. And, to evaluate the relation of this response according to the skin reaction (healing with ulcer or dry crust).

METHODS

prospective pase II, observational clinical study of 56 patients with metastases of head-and-neck squamous cell carcinoma (n=13), papillary thyroid carcinoma (n=4), adenoid cystic carcinoma of parotid gland (n=1) or malignant melanoma (n=37, 5 in head). Patients were treated by electrochemotherapy (application of electrical pulses into the tumor) after the administration of a single intravenous dose of bleomycin. Kaplan-Meier curves were performed. The statistical significance was evaluated using log-rank test; p-value of less than 0.05 was considered as significant.

RESULTS

Overall clinical response was observed in 47 patients (84%). Local side effects were mild in all the patients. Ten patients (76.9%) with neck metastasis of squamous cell carcinoma had some degree of response, but only in one was complete. Patients even with only partial response had a higher overall survival than patients without response (p= 0.02). Most of the patients with squamous cell carcinoma had diminution of pain and anxiety. Response rate and overall survival was higher in MM patients (86.5%) than in squamous cell cancer patients (76.9%) (p= 0.043). The healing process (dry crust/ulcer) was not associated with the overall survival (p= 0.86).

CONCLUSIONS

Electrochemotherapy is associated a higher overall survival and diminution of pain and anxiety. Therefore, it is an option as palliative treatment for patients with neck metastasis of squamous cell carcinoma refractory to other therapies or even as a concomitant treatment with newer immunotherapies. The type of healing of the surgical wound could not be associated with a higher rate of response or survival.

LEVEL OF EVIDENCE

III.

A real-world case-control study on the efficacy and safety of pulsed field ablation for atrial fibrillation

OBJECTIVE

The primary objective of this study was to evaluate the efficacy and safety of pulsed field ablation in individuals diagnosed with atrial fibrillation.

METHODS

A total of 36 patients diagnosed with atrial fibrillation were enrolled in the pulsed field ablation group, while another 36 patients diagnosed with atrial fibrillation were included in the radiofrequency ablation group. Among the study participants, 15 patients in the pulsed field ablation group and 17 patients in the radiofrequency ablation group had persistent atrial fibrillation. Comprehensive comparisons were made between the two groups, including baseline data, underlying diseases, medication usage, intraoperative parameters, and atrial fibrillation recurrence rates at 1, 3, and 6 months during the postoperative follow-up period.

RESULTS

(1) There were no significant differences observed between the two groups concerning baseline data and antiarrhythmic drug usage (P > 0.05); (2) the effective ablation time for both left and right pulmonary veins in the pulsed field ablation group was markedly shorter compared to the radiofrequency ablation group (P < 0.001 for each vein); (3) within the pulsed field ablation group, the number of discharges, catheter operation time, and effective ablation time for the left pulmonary vein were significantly higher than those for the right pulmonary vein (P < 0.05). Conversely, in the radiofrequency ablation group, the number of discharges for the left pulmonary vein was significantly higher than that for the right pulmonary vein (P < 0.05); and (4) when comparing sinus rhythm maintenance at 1, 3, and 6 months postoperatively, no statistically significant differences were noted between the two groups for paroxysmal, persistent, and paroxysmal + persistent atrial fibrillation cases (P > 0.05).

CONCLUSION

During the 6-month follow-up period, pulsed field ablation demonstrated comparable efficacy to radiofrequency ablation with respect to recurrence rates for both paroxysmal and persistent atrial fibrillation. Moreover, pulsed field ablation exhibited high safety levels, excellent surgical efficiency, and a notably brief learning curve, affirming its viability as a therapeutic option for these conditions.

Preclinical evaluation of a novel single-shot pulsed field ablation system for pulmonary vein and atrial ablation

INTRODUCTION

Pulsed field ablation (PFA) is a nonthermal ablative strategy that achieves cell death via electroporation. Herein, we investigated the preclinical safety and efficacy of PFA using two novel 8-French, 16-electrode spiral PFA/mapping catheters (ElePulse; CRC EP, Inc.).

METHODS

Bipolar PFA (>1.8 kV) was performed using 30 s, single-shot, QRS-gated applications. Altogether, 94 atrial structures were ablated in 23 swine, one canine, and one ovine, including right and left atria and atrial appendages, pulmonary veins, and superior and inferior (IVC) vena cavae. We also examined the impact of PFA on the phrenic nerve (14 swine) and on a deviated esophagus after delivery of PFA from inside the IVC (five swine).

RESULTS

All applications were single-shot without catheter repositioning. Minimal microbubbling was observed without significant skeletal muscle twitching/activation (mean acceleration: 0.05 m/s2 ). There was a marked reduction in post-PFA versus pre-PFA atrial electrogram amplitude (0.17 ± 0.21 vs. 1.18 ± 1.08 mV; p < .0001). Lesion durability was demonstrated up to 3 months in all targeted tissues. Histologically, lesions were contiguous and transmural, except in the atrial appendage, and without any thermal effects. Magnetic resonance, gross, and histologic examinations of the brain, rete mirabile, and kidneys revealed no thromboembolism. No acute/long-term phrenic nerve dysfunction was encountered. Although within 2 h of ablation, histologic examinations of the esophagus revealed acute PFA-related changes in the muscular layer, these completely resolved by 21 ± 5 days.

CONCLUSION

A novel, single-shot, spiral PFA system is capable of safely creating large, durable atrial lesions without significant adverse effects on the phrenic nerve or the esophagus.

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.

Electrochemotherapy vs radiotherapy in the treatment of primary cutaneous malignancies or cutaneous metastases from primary solid organ malignancies: A systematic review and narrative synthesis

BACKGROUND

Electrochemotherapy has gained international traction and commendation in national guidelines as an effective tool in the management of cutaneous malignancies not amenable to surgical resection. Despite this, no level 5 evidence exists comparing it to radiotherapy in the treatment of cutaneous malignancies. This systematic review aimed to examine the literature directly and indirectly comparing electrochemotherapy and radiotherapy in the treatment of primary cutaneous malignancies or cutaneous metastases from primary solid organ malignancies.

MATERIALS & METHODS

The protocol for this review was registered on the PROSPERO International Prospective Register of Systematic Reviews with the protocol ID CRD42021285415. Searches of MEDLINE, Embase, CINAHL, CENTRAL and ClinicalTrials.gov databases were undertaken from database inception to 28 December 2021. Studies in humans comparing treatment with electrochemotherapy to radiotherapy and reporting tumour response with a minimum four week follow-up were eligible. Risk of bias was assessed using the ROBINS-I tool. Results are provided as a narrative synthesis.

RESULTS

Two case series with a total of 92 patients were identified as relevant to this study. Both case series examined patients with cutaneous squamous cell carcinoma. One case series examined elderly patients with predominantly head/neck lesions. The other examined younger patients with predominantly limb lesions who had cutaneous squamous cell carcinoma directly attributable to a rare skin condition.

CONCLUSION

There is little literature presenting comparative data for electrochemotherapy and radiotherapy in the treatment of primary cutaneous malignancies or cutaneous metastases. Included studies were marred by serious risk of bias particularly due to confounding. The inherent bias and heterogeneity of the included studies precluded synthesis of a consolidated comparison of clinical outcomes between the two therapies. Further research is required in this domain in the form of clinical trials and observational studies to inform guidelines for electrochemotherapy treatment.

Nanoporous electroporation needle for localized intracellular delivery in deep tissues

The exogenous control of intracellular drug delivery has been shown to improve the overall efficacy of therapies by reducing nonspecific off-target toxicity. However, achieving a precise on-demand dosage of a drug in deep tissues with minimal damage is still a challenge. In this study, we report an electric-pulse-driven nanopore-electroporation (nEP) system for the localized intracellular delivery of a model agent in deep tissues. Compared with conventional bulk electroporation, in vitro nEP achieved better transfection efficiency (>60%) with a high cell recovery rate (>95%) under a nontoxic low electroporation condition (40 V). Furthermore, in vivo nEP using a nanopore needle electrode with a side drug-releasing compartment offered better control over the dosage release, time, and location of propidium iodide, which was used as a model agent for intracellular delivery. In a pilot study using experimental animals, the nEP system exhibited two times higher transfection efficiency of propidium iodide in the thigh muscle tissue, while minimizing tissue damage (<20%) compared to that of bulk electroporation. This tissue-penetrating nEP platform can provide localized, safe, and effective intracellular delivery of diverse therapeutics into deep tissues in a controlled manner.

High-Frequency Electroporation and Chemotherapy for the Treatment of Cutaneous Malignancies: Evaluation of Early Clinical Response

High-frequency electroporation (HF-EP) with chemotherapy is a novel therapy proposed for both curative and palliative treatment of cutaneous malignancies. The use of high-frequency biphasic pulses is thought to reduce the painful muscle contractions associated with traditional electrochemotherapy (ECT), allowing treatment administration under local anaesthesia. This proof-of-concept study investigated the efficacy and tolerability of HF-EP protocols on a variety of cutaneous malignancies. A total of 97 lesions of five different histological subtypes were treated across 25 patients. At 12 weeks post-treatment, a 91.3% overall lesion response rate was observed (complete response: 79%; partial response: 12.3%), with excellent intraprocedural patient tolerability under local anaesthetic. HF-EP with chemotherapy shows promising results regarding tumour response rates for cutaneous malignancies of varying histological subtypes when compared to traditional ECT protocols. Improved patient tolerability is important, increasing the possibility of treatment delivery under local anaesthesia and potentially broadening the treatment envelope for patients with cutaneous malignancies.

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.

Electroporation Enhances the Anticancer Effects of Novel Cu(II) and Fe(II) Complexes in Chemotherapy-Resistant Glioblastoma Cancer Cells

Schiff base ligand (L) was obtained by condensation reaction between 4-aminopyrimidin-2(1H)-one (cytosine) with 2-hydroxybenzaldehyde. The synthesized Schiff base was used for complexation with Cu(II) and Fe(II) ions used by a molar (2 : 1 mmol ration) in methanol solvent. The structural features of ligand, Cu(II), and Fe(II) metal complexes were determined by standard spectroscopic methods (FT-IR, elemental analysis, proton and carbon NMR spectra, UV/VIS, and mass spectroscopy, magnetic susceptibility, thermal analysis, and powder X-ray diffraction). The synthesized compounds (Schiff base and its metal complexes) were screened in terms of their anti-proliferative activities in U118 and T98G human glioblastoma cell lines alone or in combination with electroporation (EP). Moreover, the human HDF (human dermal fibroblast) cell lines was used to check the bio-compatibility of the compounds. Anti-proliferative activities of all compounds were ascertained using an MTT assay. The complexes exhibited a good anti-proliferative effect on U118 and T98G glioblastoma cell lines. In addition, these compounds had a negligible cytotoxic effect on the fibroblast HDF cell lines. The use of compounds in combination with EP significantly decreased the IC₅₀ values compared to the use of compounds alone (p<0.05). These results show that newly synthesized Cu(II) and Fe(II) complexes can be developed for use in the treatment of chemotherapy-resistant U118 and T98G glioblastoma cells and that treatment with lower doses can be provided when used in combination with EP.

Synergistic In Vitro Anticancer Toxicity of Pulsed Electric Fields and Glutathione

Despite continuous advancement in skin cancer therapy, the disease is still fatal in many patients, demonstrating the need to improve existing therapies, such as electrochemotherapy (ECT). ECT can be applied in the palliative or curative setting and is based on the application of pulsed electric fields (PEF), which by themselves exerts none to low cancer toxicity but become potently toxic when combined with low-dosed chemotherapeutics such as bleomycin and cisplatin. Albeit their favorable side-effect profiles, not all patients respond to standard ECT, and some responders experience tumor recurrence. To identify potential adjuvant or alternative agents to standard electrochemotherapy, we explored the possibility of combining PEF with a physiological compound, glutathione (GSH), to amplify anticancer toxicity. GSH is an endogenous antioxidant and is available as a dietary supplement. Surprisingly, neither GSH nor PEF mono treatment but GSH + PEF combination treatment exerted strong cytotoxic effects and declined metabolic activity in four skin cancer cell lines in vitro. The potential applicability to other tumor cells was verified by corroborating results in two leukemia cell lines. Strikingly, GSH + PEF treatment did not immediately increase intracellular GSH levels, while levels 24 h following treatment were enhanced. Similar tendencies were made for intracellular reactive oxygen species (ROS) levels, while extracellular ROS increased following combination treatment. ROS levels and the degree of cytotoxicity could be partially reversed by pre-incubating cells with the NADPH-oxidase (NOX) inhibitor diphenyleneiodonium (DPI) and the H₂O₂-degrading enzyme catalase. Collectively, our findings suggest a promising new "endogenous" drug to be combined with PEF for future anticancer research approaches.

Successful electrochemotherapy treatment of a large bleeding lymph node melanoma metastasis

Despite the progress in immunotherapy and targeted therapy for patients with cutaneous malignant melanoma not all patients with loco-regional recurrences will respond to treatment. Electrochemotherapy is a relatively new treatment modality where the efficacy of a chemotherapeutic drug is enhanced by an electrical field. Here we report a case of a 68-year-old woman with a large therapy resistant inguinal lymph node melanoma metastasis complicated by bleeding that was successfully treated with electrochemotherapy.

Electrochemotherapy of Primary Colon Rectum Cancer and Local Recurrence: Case Report and Prospective Analysis

Purpose: Surgery, radiotherapy, and oncological treatment (chemotherapy and antineoplastic antibodies) are standard treatments of rectal cancer. ECT has shown its effectiveness and suitability in deep solid tumors conducted in both preclinical and clinical studies. We show here an update and preliminary results with locally advanced rectum cancer (LARC) treated with ECT. Methods: Two patients with major clinical response to restaging after neoadjuvant treatment for LARC were subjected to ECT 12 weeks after completing chemo-radiation therapy. One patient was subjected to ECT on a colorectal local recurrence formed after neoadjuvant treatment for LARC and surgery. Computed Tomography and Magnetic Resonance Imaging were used to assess ECT response. Results: The results showed stable disease in two of the three patients treated, while one patient achieved a complete response. The local control of disease is maintained in the patient follow-up. For each patient, a reduction in pain was observed and for the patient with local recurrence, a reduction in bleeding present before ECT was also achieved. Conclusion: Preliminary results showed that ECT is a safe and effective treatment in patients with a major clinical response or local recurrence after neoadjuvant therapy for LARC and allows a reduction in pain and bleeding with a consequent improvement to quality of life.

Impact of electrochemotherapy in metastatic cutaneous melanoma: a contemporary systematic review and meta-analysis

BACKGROUND

Electrochemotherapy (ECT) harnesses electric pulses to enhance cytotoxic drug delivery into tumors and has entered the armamentarium to treat superficially metastatic melanoma. We performed a systematic review and meta-analysis to assess treatment patterns and patient outcomes.

METHODS

PubMed, Medline, Embase, and the Cochrane Library databases were queried for publication from inception to September 2020. Primary outcome measures were overall and complete response rate (ORR and CRR); secondary outcomes included local control rate (LCR) and overall survival (OS).

RESULTS

Twenty-seven studies met the selection criteria for a total of 1161 individuals (mean age 71 years) and 5308 tumors (weighted mean size 14 mm). The majority of patients (n = 1124) underwent bleomycin-ECT. Aggregate ORR was 77.6% (95% confidence interval [CI] 71.0 - 83.2%) and CRR 48% (95% CI 42 - 54%), with no significant difference between the route of bleomycin administration (ORR, 69.2 vs. 81.9% following intravenous or intratumoral bleomycin, p = .37) and tumor size (p = .69). When reported (n = 8 studies), 1- and 2-year LCR ranged from 54 to 89% and 72 to 74%, respectively, and 1-year OS (n = 3 studies) from 67 to 89%.

CONCLUSIONS

ECT with either intratumoral or intravenous bleomycin confers a high therapeutic response in cutaneous metastatic melanoma. Moderate evidence supports its low toxicity and durability of local control.HighlightsElectrochemotherapy (ECT) is associated with a 77% overall response rate (ORR).Intravenous and intratumoral bleomycin are equally effective.There are no relevant toxicity concerns.One-year local tumor control rate ranges from 54 to 89%.Current literature has significant variation in reporting.

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.

Bleomycin Electrosclerotherapy Treatment in the Management of Vascular Malformations

BACKGROUND

Intralesional injection of a sclerosing agent is a standard treatment for vascular malformations, but many repeat treatments are often required to achieve a response. The temporary application of an electrical field to the treated area increases cellular membrane permeability and therefore augments drug delivery.

OBJECTIVE

To report a case series of patients with vascular malformations who received bleomycin electrosclerotherapy (EST).

MATERIALS AND METHODS

A prospective observational case series of patients with vascular malformations treated with bleomycin EST. Only patients who did not respond or had limited response to standard sclerotherapy were included. The response to the treatment was assessed using a global assessment score and patient-reported outcome measures.

RESULTS

Thirty patients were treated with EST. Most of the patients had venous malformations (57%). Complete response or significant improvement was observed in 17 (57%) and 7 (23%) patients, respectively. Most of the patients were satisfied or very much satisfied with the outcome of the treatment. Most commonly reported complications were swelling, pain, and bleeding.

CONCLUSION

Electrosclerotherapy is a promising method of augmenting the efficacy of intralesional bleomycin injections when treating vascular malformations. It can potentially lead to a reduction in the administered dose and number of treatment sessions needed.

A Multicenter Randomized Controlled Prospective Study to Assess Efficacy of Laparoscopic Electrochemotherapy in the Treatment of Locally Advanced Pancreatic Cancer

Background: Eighty percent of patients with pancreatic adenocarcinoma present a locally advanced or metastatic disease at diagnosis and are not eligible for surgery if not with palliative intent. In cases of locally advanced disease (LAPC), the combination of chemo and radiotherapy is the only therapeutic option and correlates with a median survival of 15 months (10 months without treatment), with partial remission of disease in 50% of cases. The feasibility and safety of Electrochemotherapy (ECT) have been demonstrated in the treatment of deep tumors. Aim: The aim of the study is to evaluate the efficacy of electrochemotherapy (ECT) followed by conventional systemic treatment compared to the only conventional systemic treatment in LAPC in terms of objective response and overall survival. Patients and Methods: This study is a phase IIb prospective multicenter randomized controlled trial with two arms. The study will include 90 patients: 45 in the control group and 45 in the experimental group. Patients with LAPC in the control arm will receive conventional chemotherapy (FOLFOXIRI). Patients with LAPC in the experimental arm will be subjected to Electrochemotherapy and subsequently to FOLFOXIRI. The objective response at 30, 90, and 180 days from treatment will be based on the computed tomography (CT), magnetic resonance (MR), and positron emission tomography/CT response (PET/CT). The objective long-term treatment response will be evaluated with the modified response evaluation criteria in solid tumors (m-RECIST) criteria, which will take into account the difference in vascularization, determined by the images obtained by CT and MR of the tumor treated before and after ECT. Conclusions: Not resectable liver metastasis, pancreatic tumors, and locally advanced renal carcinomas can be treated with laparoscopic electrodes. ECT could represent an effective therapeutic option for patients not eligible for surgery susceptible to be managed only with palliative therapies.

Safety and efficacy of electrochemotherapy in a series of patients with nonmetastasized primary or recurrent anorectal malignant melanoma

Anorectal malignant melanoma (AMM) is a rare malignant tumor. Surgery remains the gold standard but new adjuvant treatments to allow local sphincter-saving are warranted. Electrochemotherapy (ECT) is an alternative to surgery in selected cohorts of patients. To evaluate safety and efficacy of ECT in a retrospective series of patients with primary or recurrent AMM in terms of local disease control, local progression free and overall survival. Seven primary and one recurrent AMM underwent ECT. Patients were followed at 1 and 2 months and at the longest available follow-up with clinical examination and/or ultrasound. One month after ECT 6/8 (75%) patients showed complete response, 1/8 partial response (12.5%) and 1/8 stable disease (12.5%), confirmed at 2 months. Bleeding stopped in all patients, and pain was absent or mild/moderate in all patients. No serious adverse events were observed. At 1 year of follow-up seven out of eight patients were alive (87.5%), four were disease-free and three were alive with disease. At the longest available follow-up (mean 4.9 ± 2.0 years) five out of eight (62.5%) of patients were still alive. Our study showed that ECT is well tolerated and effective in the treatment of patients with anal melanoma with good local control of disease.

Electroporation of suspension cell lines - A proposed assay set for optimizations

To make in vitro single cell electroporation protocols more comparable between various cancer types and groups, we propose a set of assays to test a range of electric field strengths at the start of any new project to determine the optimal electric field strength for a given cell line. While testing a range of electric field strengths, we kept the other ESOPE parameters constant (8 pulses, 100 µs pulse duration, 1 Hz pulse frequency). Basic assays were employed to measure short-term viability, effectiveness of treatment, metabolic activity, and recovery potential post-treatment to determine the optimal field strength for a particular cell line. Six cancer cell lines were tested, three of human (A549, A375 and Pan02) and three murine (LLC, B16F10 and MIA-PACA2). Our findings demonstrate that the optimal electroporation setting while keeping with all other ESOPE parameters are 800 V/cm for A549 and Pan02, 700 V/cm for A375, Mia-PACA2, and B16F10, and 1300 V/cm for LLC. Having an agreed upon set of assays to determine each cell lines optimal electric field strength should allow an improve translation of findings between cell lines for in vitro work from various groups and potentially improve translation into the clinic.

Bleomycin Concentration in Patients' Plasma and Tumors after Electrochemotherapy. A Study from InspECT Group

The plasma concentration profile of bleomycin in the distribution phase of patients younger than 65 years is needed to determine the suitable time interval for efficient application of electric pulses during electrochemotherapy. Additionally, bleomycin concentrations in the treated tumors for effective tumor response are not known. In this study, the pharmacokinetic profile of bleomycin in the distribution phase in 12 patients younger than 65 years was determined. In 17 patients, the intratumoral bleomycin concentration was determined before the application of electric pulses. In younger patients, the pharmacokinetics of intravenously injected bleomycin demonstrated a faster plasma clearance rate than that in patients older than 65 years. This outcome might indicate that the lowering of the standard bleomycin dose of 15,000 IU/m² with intravenous bleomycin injection for electrochemotherapy is not recommended in younger patients. Based on the plasma concentration data gathered, a time interval for electrochemotherapy of 5-15 min after bleomycin injection was determined. The median bleomycin concentration in tumors 8 min after bleomycin injection, at the time of electroporation, was 170 ng/g. Based on collected data, the reduction of the bleomycin dose is not recommended in younger patients; however, a shortened time interval for application of electric pulses in electrochemotherapy to 5-15 min after intravenous bleomycin injection should be considered.

Electrochemotherapy and Other Clinical Applications of Electroporation for the Targeted Therapy of Metastatic Melanoma

Electrochemotherapy (ECT) is an effective bioelectrochemical procedure that uses controlled electrical pulses to facilitate the increase of intracellular concentration of certain substances (electropermeabilization/ reversible electroporation). ECT using antitumor drugs such as bleomycin and cisplatin is a minimally invasive targeted therapy that can be used as an alternative for oncologic patients not eligible for surgery or other standard therapies. Even though ECT is mainly applied as palliative care for metastases, it may also be used for primary tumors that are unresectable due to size and location. Skin neoplasms are the main clinical indication of ECT, the procedure reporting good curative results and high efficiency across all tumor types, including melanoma. In daily practice, there are many cases in which the patient’s quality of life can be significantly improved by a safe procedure such as ECT. Its popularity must be increased because it has a safe profile and minor local adverse reactions. The method can be used by dermatologists, oncologists, and surgeons. The aim of this paper is to review recent literature concerning electrochemotherapy and other clinical applications of electroporation for the targeted therapy of metastatic melanoma.

Generation of Tumor-activated T cells using electroporation

Expansion of cytotoxic T lymphocytes (CTLs) is a crucial step in almost all cancer immunotherapeutic methods. Current techniques for expansion of tumor-reactive CTLs present major limitations. This study introduces a novel method to effectively produce and expand tumor-activated CTLs using high-voltage pulsed electric fields. We hypothesize that utilizing high-voltage pulsed electric fields may be an ideal method to activate and expand CTLs due to their non-thermal celldeath mechanism. Tumor cells were subjected to high-frequency irreversible electroporation (HFIRE) with various electric field magnitudes (1250, 2500 V/cm) and pulse widths (1, 5, and 10 µs), or irreversible electroporation (IRE) at 1250 V/cm. The treated tumor cells were subsequently cocultured with CD4+ and CD8+ T cells along with antigen-presenting cells. We show that tumor-activated CTLs can be produced and expanded when exposed to treated tumor cells. Our results suggest that CTLs are more effectively expanded when pulsed with HFIRE conditions that induce significant cell death (longer pulse widths and higher voltages). Activated CD8+ T cells demonstrate cytotoxicity to untreated tumor cells suggesting effector function of the activated CTLs. The activated CTLs produced with our technique could be used for clinical applications with the goal of targeting and eliminating the tumor.

Clinical Applications and Immunological Aspects of Electroporation-Based Therapies

Reversible electropermeabilization (RE) is an ultrastructural phenomenon that transiently increases the permeability of the cell membrane upon application of electrical pulses. The technique was described in 1972 by Neumann and Rosenheck and is currently used in a variety of applications, from medicine to food processing. In oncology, RE is applied for the intracellular transport of chemotherapeutic drugs as well as the delivery of genetic material in gene therapies and vaccinations. This review summarizes the physical changes of the membrane, the particularities of bleomycin, and the immunological aspects involved in electrochemotherapy and gene electrotransfer, two important EP-based cancer therapies in human and veterinary oncology.

Tumor perfusion evaluation using dynamic contrast-enhanced ultrasound after electrochemotherapy and IL-12 plasmid electrotransfer in murine melanoma

Electrochemotherapy with bleomycin (ECT BLM) is an effective antitumor treatment already used in clinical oncology. However, ECT alone is still considered a local antitumor therapy because it cannot induce systemic immunity. When combined with adjuvant gene electrotransfer of plasmid DNA encoding IL-12 (GET pIL-12), the combined therapy leads to a systemic effect on untreated tumors and distant metastases. Although the antitumor efficacy of both therapies alone or in combination has been demonstrated at both preclinical and clinical levels, data on the predictors of efficacy of the treatments are still lacking. Herein, we evaluated the results of dynamic contrast-enhanced ultrasound (DCE-US) as a predictive factor for ECT BLM and GET pIL-12 in murine melanoma. Melanoma B16F10 tumors grown in female C57Bl/6NCrl mice were treated with GET pIL-12 and ECT BLM. Immediately after therapy, 6 h and 1, 3, 7 and 10 days later, tumors were examined by DCE-US. Statistical analysis was performed to inspect the correlation between tumor doubling time (DT) and DCE-US measurements using semilinear regression models and Bland-Altman plots. Therapeutic groups in which DCE-US showed reduced tumor perfusion had longer tumor DTs. It was confirmed that the DCE-US parameter peak enhancement (PE), reflecting relative blood volume, had predictive value for the outcome of therapy: larger PE correlated with shorter DT. In addition, perfusion heterogeneity was also associated with outcome: tumors that had more heterogeneous perfusion had faster growth, i.e., shorter DTs. This study demonstrates that DCE-US can be used as a method to predict the efficacy of electroporation-based treatment.

Organ Sparing for Locally Advanced Rectal Cancer after Neoadjuvant Treatment Followed by Electrochemotherapy

Simple Summary

This is a Phase II randomized controlled trial conducted with the aim of investigating whether the use of Electrochemotherapy after neoadjuvant therapy (ECT) and before surgery in patients with major clinical response allows for a more conservative surgical approach in patients with Locally Advanced Rectal Cancer (LARC) in comparison with the control group that will not receive ECT. The treatment response, in both the control arm and in the treatment arm, will be assessed using the histopathological tumor regression grade on tissue specimens after local excision.

Abstract

Background: Currently, 45–55% of rectal cancer patients receive preoperative chemo- radio-therapy for Locally Advanced Rectal Cancer (LARC). The idea of our study is to use Electrochemotherapy (ECT) before surgery, in patients with major clinical response after neoadjuvant therapy, to allow for a more conservative surgical approach. Objective: To evaluate the increase of the complete response rate after neoadjuvant treatment in LARC and to spare organ function due to total mesorectal excision (TME). Patients and Methods: This is a Phase II randomized controlled trial enrolling 70 patients that will be developed in two stages. In the first step, 28 patients will be enrolled: 14 of these will receive ECT for four weeks after neo-adjuvant treatment and then local excision (treatment group) and 14 patients will receive neo-adjuvant treatment and then local excision (control group). If an increase of response rate is observed in the first stage, and/or feasibility/safety is demonstrated, the second stage of the trial will be performed, enrolling an additional 42 patients. The treatment response. in both the control arm and the treatment arm, will be assessed using the histopathological tumor regression grade on tissue specimens after local excision.

To Close or to Collapse: The Role of Charges on Membrane Stability upon Pore Formation

Resealing of membrane pores is crucial for cell survival. Membrane surface charge and medium composition are studied as defining regulators of membrane stability. Pores are generated by electric field or detergents. Giant vesicles composed of zwitterionic and negatively charged lipids mixed at varying ratios are subjected to a strong electric pulse. Interestingly, charged vesicles appear prone to catastrophic collapse transforming them into tubular structures. The spectrum of destabilization responses includes the generation of long-living submicroscopic pores and partial vesicle bursting. The origin of these phenomena is related to the membrane edge tension, which governs pore closure. This edge tension significantly decreases as a function of the fraction of charged lipids. Destabilization of charged vesicles upon pore formation is universal-it is also observed with other poration stimuli. Disruption propensity is enhanced for membranes made of lipids with higher degree of unsaturation. It can be reversed by screening membrane charge in the presence of calcium ions. The observed findings in light of theories of stability and curvature generation are interpreted and mechanisms acting in cells to prevent total membrane collapse upon poration are discussed. Enhanced membrane stability is crucial for the success of electroporation-based technologies for cancer treatment and gene transfer.

Reduction of muscle contraction and pain in electroporation-based treatments: An overview

BACKGROUND

In the first studies of electrochemotherapy (ECT), small cutaneous metastases were treated and only mild or moderate pain was observed; therefore, pain was not considered a significant issue. As the procedure began to be applied to larger cutaneous metastases, pain was reported more frequently. For that reason, reduction of both muscle contractions and pain have been investigated over the years.

AIM

To present an overview of different protocols described in literature that aim to reduce muscle contractions and pain caused by the electroporation (EP) effect in both ECT and irreversible EP treatments.

METHODS

Thirty-three studies published between January 1999 and November 2020 were included. Different protocol designs and electrode geometries that reduce patient pain and the number of muscle contractions and their intensity were analysed.

RESULTS

The analysis showed that both high frequency and bipolar/biphasic pulses can be used to reduce pain and muscle contractions in patients who undergo EP treatments. Moreover, adequate electrode design can decrease EP-related morbidity. Particularly, needle length, diameter and configuration of the distance between the needles can be optimised so that the muscle volume crossed by the current is reduced as much as possible. Bipolar/biphasic pulses with an inadequate pulse length seem to have a less evident effect on the membrane permeability compared with the standard pulse protocol. For that reason, the number of pulses and the voltage amplitude, as well as the pulse duration and frequency, must be chosen so that the dose of delivered energy guarantees EP efficacy.

CONCLUSION

Pain reduction in EP-based treatments can be achieved by appropriately defining the protocol parameters and electrode design. Most results can be achieved with high frequency and/or bipolar/biphasic pulses. However, the efficacy of these alternative protocols remains a crucial point to be assessed further.

A Systematic Review about Imaging and Histopathological Findings for Detecting and Evaluating Electroporation Based Treatments Response

BACKGROUND

Imaging methods and the most appropriate criteria to be used for detecting and evaluating response to oncological treatments depend on the pathology and anatomical site to be treated and on the treatment to be performed. This document provides a general overview of the main imaging and histopathological findings of electroporation-based treatments (Electrochemotherapy-ECT and Irreversible electroporation-IRE) compared to thermal approach, such as radiofrequency ablation (RFA), in deep-seated cancers with a particular attention to pancreatic and liver cancer.

METHODS

Numerous electronic datasets were examined: PubMed, Scopus, Web of Science and Google Scholar. The research covered the years from January 1990 to April 2021. All titles and abstracts were analyzed. The inclusion criteria were the following: studies that report imaging or histopathological findings after ablative thermal and not thermal loco-regional treatments (ECT, IRE, RFA) in deep-seated cancers including pancreatic and liver cancer and articles published in the English language. Exclusion criteria were unavailability of full text and congress abstracts or posters and different topic respect to inclusion criteria.

RESULTS

558 potentially relevant references through electronic searches were identified. A total of 38 articles met the inclusion criteria: 20 studies report imaging findings after RFA or ECT or IRE in pancreatic and liver cancer; 17 studies report histopathological findings after RFA or ECT or IRE; 1 study reports both imaging and histopathological findings after RFA or ECT or IRE.

CONCLUSIONS

Imaging features are related to the type of therapy administrated, to the timing of re-assessment post therapy and to the imaging technique being used to observe the effects. Histological findings after both ECT and IRE show that the treated area becomes necrotic and encapsulated in fibrous tissue, suggesting that the size of the treated lesion cannot be measured as an endpoint to detect response. Moreover, histology frequently reported signs of apoptosis and reduced vital tissue, implying that imaging criteria, which take into account the viability and not the size of the lesion, are more appropriate to evaluate response to treatment.

Malignant Skin Cancer Excision in Combined Therapy with Electro-Chemotherapy and Dermal Substitute

Squamous cell carcinoma (SCC) is the second most common malignancy skin cancer. It is characterized by abnormal, accelerated growth of squamous cells (SCs). SCC occurs when DNA damage from exposure to ultraviolet radiation or other damaging agents trigger abnormal changes in the SCs, presenting as painless lesions on areas of high sun exposure, such as the dorsum of the hand and upper extremity. For most skin SCC, the surgical excision alone is standard practice. However, recent efforts in new treatment strategies have involved around adjuvant or concomitant electrochemotherapy (ECT). ECT is a non-thermal tumor ablation modality, safe and effective on any type of solid tumor. An 87-year-old patient affected by hand SCC with invasion of deep structures including tendons was treated with neoadjuvant intra-tumoral ECT sessions followed by a selective surgical removal and reconstruction of the substance loss with collagen dermal template (CDT). Two neoadjuvant intra-tumoral ECT procedures, at distance of 3 months, with the aim to reduce the tumor size before a selective surgery, were performed. This study shows that combined surgical selective excision with ECT and CDT is a valid technique for the extended-deep dorsal hand tumor lesions reconstruction.

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.

Rapid Impedance Spectroscopy for Monitoring Tissue Impedance, Temperature, and Treatment Outcome During Electroporation-Based Therapies

OBJECTIVE

Electroporation-based therapies (EBTs) employ high voltage pulsed electric fields (PEFs) to permeabilize tumor tissue; this results in changes in electrical properties detectable using electrical impedance spectroscopy (EIS). Currently, commercial potentiostats for EIS are limited by impedance spectrum acquisition time (  ∼ 10 s); this timeframe is much larger than pulse periods used with EBTs (  ∼ 1 s). In this study, we utilize rapid EIS techniques to develop a methodology for characterizing electroporation (EP) and thermal effects associated with high-frequency irreversible EP (H-FIRE) in real-time by monitoring inter-burst impedance changes.

METHODS

A charge-balanced, bipolar rectangular chirp signal is proposed for rapid EIS. Validation of rapid EIS measurements against a commercial potentiostat was conducted in potato tissue using flat-plate electrodes and thereafter for the measurement of impedance changes throughout IRE treatment. Flat-plate electrodes were then utilized to uniformly heat potato tissue; throughout high-voltage H-FIRE treatment, low-voltage inter-burst impedance measurements were used to continually monitor impedance change and to identify a frequency at which thermal effects are delineated from EP effects.

RESULTS

Inter-burst impedance measurements (1.8 kHz - 4.93 MHz) were accomplished at 216 discrete frequencies. Impedance measurements at frequencies above  ∼ 1 MHz served to delineate thermal and EP effects in measured impedance.

CONCLUSION

We demonstrate rapid-capture ( 1 s) EIS which enables monitoring of inter-burst impedance in real-time. For the first time, we show impedance analysis at high frequencies can delineate thermal effects from EP effects in measured impedance.

SIGNIFICANCE

The proposed waveform demonstrates the potential to perform inter-burst EIS using PEFs compatible with existing pulse generator topologies.