Rapid dramatic alterations to the tumor microstructure in pancreatic cancer following irreversible electroporation ablation

Influence of electroporation parameters on the reaction and transport mechanisms in electro-chemotherapeutic treatments using Boolean modeling and the Method of Fundamental Solutions

The systemic administration of chemotherapeutic drugs involves some reaction and transport mechanisms (RTMs), including perfusion along the blood vessels, extravasation, lymphatic drainage, interstitial and transmembrane transport, and protein association and dissociation, among others. When tissue is subjected to the controlled application of electric pulses (electroporation), the vessel wall and cell membrane are permeabilized, capillaries are vasoconstricted and tissue porosity is modified, affecting the RTMs during electro-chemotherapeutic treatments. This study is a theoretical investigation about the influence of the electric field magnitude (E), number of electroporation treatments (Nep) and duration of each electroporation protocol (Tep) on the presence, interaction and rates of the RTMs using in-house computational tools. Firstly, the ratios between the extracellular, free intracellular and bound intracellular concentrations are calculated by solving the species conservation equations of a tumor cord domain by the Method of Fundamental Solutions (MFS), which was implemented, calibrated and validated in a previous work. Then, a Boolean model, which is founded on the comparison of the spatio-temporal evolution of concentration ratios, is proposed here to explore the interaction between RTMs. Different combinations of E=[0kV/m,46kV/m,70kV/m], Nep=[6,8,12] and Tep=[5min,10min,15min] are tested here. The MFS results indicate that Nep and Tep do not have a relevant influence on the types and relative importance of RTMs, but only on the rates of these mechanisms. In general, increasing E reduces the radial uniformity of transmembrane transport and association rates regarding the non-electroporated tissue, whereas the axial uniformity is affected in a lower extent.

Dendritic cell vaccination combined with irreversible electroporation for treating pancreatic cancer-a narrative review

Background and Objective

Pancreatic ductal adenocarcinoma (PDAC) is 3rd most lethal cancer in the USA leading to a median survival of six months and less than 5% 5-year overall survival (OS). As the only potentially curative treatment, surgical resection is not suitable for up to 90% of the patients with PDAC due to late diagnosis. Highly fibrotic PDAC with an immunosuppressive tumor microenvironment restricts cytotoxic T lymphocyte (CTL) infiltration and functions causing limited success with systemic therapies like dendritic cell (DC)-based immunotherapy. In this study, we investigated the potential benefits of irreversible electroporation (IRE) ablation therapy in combination with DC vaccine therapy against PDAC.

Methods

We performed a literature search to identify studies focused on DC vaccine therapy and IRE ablation to boost therapeutic response against PDAC indexed in PubMed, Web of Science, and Scopus until February 20th, 2023.

Key Content and Findings

IRE ablation destructs tumor structure while preserving extracellular matrix and blood vessels facilitating local inflammation. The studies demonstrated IRE ablation reduces tumor fibrosis and promotes CTL tumor infiltration to PDAC tumors in addition to boosting immune response in rodent models. The administration of the DC vaccine following IRE ablation synergistically enhances therapeutic response and extends OS rates compared to the use of DC vaccination or IRE alone. Moreover, the implementation of data-driven approaches further allows dynamic and longitudinal monitoring of therapeutic response and OS following IRE plus DC vaccine immunoablation.

Conclusions

The combination of IRE ablation and DC vaccine immunotherapy is a potent strategy to enhance the therapeutic outcomes in patients with PDAC.

Irreversible Electroporation of the Hepatobiliary System: Current Utilization and Future Avenues

Liver cancer remains a leading cause of cancer-related deaths worldwide despite numerous advances in treatment. While surgical resection remains the gold standard for curative treatment, it is only possible for a minority of patients. Thermal ablation is an effective option for the treatment of smaller tumors; however, its use is limited to tumors that are not located in proximity to sensitive structures due to the heat sink effect and the potential of thermal damage. Irreversible electroporation (IRE) is a non-thermal ablative modality that can deliver targeted treatment and the effective destruction of tumors that are in close proximity to or even surrounding vascular or biliary ducts with minimal damage to these structures. IRE produces short pulses of high-frequency energy which opens pores in the lipid bilayer of cells leading to apoptosis and cell death. IRE has been utilized clinically for over a decade in the treatment of liver cancers with multiple studies documenting an acceptable safety profile and high efficacy rates.

Irreversible Electroporation Combined With Dendritic Cell-based Vaccines for the Treatment of Osteosarcoma

Osteosarcoma is the most common primary bone malignancy, and surgical resection combined with neoadjuvant chemotherapy is the gold-standard treatment for affected patients. Although the overall survival rates for patients with osteosarcoma currently range from 60% to 70%, outcomes remain disappointing for patients with recurrent, metastatic, or unresectable disease. Irreversible electroporation (IRE) is a novel ablation technique with the potential to elicit an immune response in solid tumors. Dendritic cell (DC)-based tumor vaccines have shown promising therapeutic efficacy in preclinical studies focused on osteosarcoma; however, only limited therapeutic efficacy has been observed in clinical trials. Thus, there is considerable potential therapeutic value in developing combination osteosarcoma treatments that involve IRE and DC-based tumor vaccines. In this review, we discuss recent advances in preclinical and clinical DC-based immunotherapies, as well as potential combinations of DC-based vaccines and IRE, that may improve therapeutic outcomes for patients with osteosarcoma.

Irreversible electroporation for the management of pancreatic cancer: Current data and future directions

Pancreatic cancer is currently the seventh leading cause of cancer death (4.5% of all cancer deaths) while 80%-90% of the patients suffer from unresectable disease at the time of diagnosis. Prognosis remains poor, with a mean survival up to 15 mo following systemic chemotherapy. Loco-regional thermal ablative techniques are rarely implemented due to the increased risk of thermal injury to the adjacent structures, which can lead to severe adverse events. Irreversible electroporation, a promising novel non-thermal ablative modality, has been recently introduced in clinical practice for the management of inoperable pancreatic cancer as a safer and more effective loco-regional treatment option. Experimental and initial clinical data are optimistic. This review will focus on the basic principles of IRE technology, currently available data, and future directions.

Effect of pulsed field ablation on solid tumor cells and microenvironment

Pulsed field ablation can increase membrane permeability and is an emerging non-thermal ablation. While ablating tumor tissues, electrical pulses not only act on the membrane structure of cells to cause irreversible electroporation, but also convert tumors into an immune active state, increase the permeability of microvessels, inhibit the proliferation of pathological blood vessels, and soften the extracellular matrix thereby inhibiting infiltrative tumor growth. Electrical pulses can alter the tumor microenvironment, making the inhibitory effect on the tumor not limited to short-term killing, but mobilizing the collective immune system to inhibit tumor growth and invasion together.

Safety and feasibility of irreversible electroporation for the pancreatic head in a porcine model

BACKGROUND

Irreversible electroporation (IRE) is a local non-thermal ablative technique which has been suggested as a potential cancer therapy. However, the specific anatomic characteristics of the pancreatic head make it challenging to perform any local ablation in this region. Therefore, the safety and feasibility of IRE in the pancreatic head region should be further explored.

AIM

To evaluate the safety of IRE in pancreatic head region including its effects on pancreatic ducts, vessels, and adjacent gastrointestinal organs.

METHODS

Eight landrace miniature pigs underwent IRE of pancreatic head tissue successfully, with a total of 16 lesions created. Laboratory testing including white blood cell (WBC) count and serum amylase before IRE with follow-up laboratory analysis and pathological examination at 1, 7, 14, and 28 d postablation were performed.

RESULTS

All pigs tolerated the ablation procedure without serious perioperative complications. Transiently elevated WBC count and amylase were observed at 24 h post-IRE, suggesting an acute pancreatic tissue damage which was confirmed by pathological observations. Vascular endothelial cells and pancreatic duct epithelial cells in ablation zone were also positive in terminal deoxynucleotidyl transferase dUTP nick end labeling staining. There was extensive duodenum mucosa damage with local hemorrhage 24 h after ablation, while regeneration of new villous structures were observed at 7 and 28 d post-IRE. Masson’s trichromatic staining showed that the extracellular matrix was still intact in vessels and pancreatic ducts, and even in the duodenum.

CONCLUSION

IRE ablation to the pancreatic head may be safe and feasible without long-term damage to the surrounding vital structures. However, risks of stress injuries in acute phase should be taken into consideration to prevent severe perioperative complications.

Locoregional therapies and their effects on the tumoral microenvironment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is expected to become the second leading cause of death from cancer by 2030. Despite intensive research in the field of therapeutics, the 5-year overall survival is approximately 8%, with only 20% of patients eligible for surgery at the time of diagnosis. The tumoral microenvironment (TME) of the PDAC is one of the main causes for resistance to antitumoral treatments due to the presence of tumor vasculature, stroma, and a modified immune response. The TME of PDAC is characterized by high stiffness due to fibrosis, with hypo microvascular perfusion, along with an immunosuppressive environment that constitutes a barrier to effective antitumoral treatment. While systemic therapies often produce severe side effects that can alter patients' quality of life, locoregional therapies have gained attention since their action is localized to the pancreas and can thus alleviate some of the barriers to effective antitumoral treatment due to their physical effects. Local hyperthermia using radiofrequency ablation and radiation therapy - most commonly using a local high single dose - are the two main modalities holding promise for clinical efficacy. Recently, irreversible electroporation and focused ultrasound-derived cavitation have gained increasing attention. To date, most of the data are limited to preclinical studies, but ongoing clinical trials may help better define the role of these locoregional therapies in the management of PDAC patients.

Electrochemotherapy of Deep-Seated Tumors: State of Art and Perspectives as Possible "EPR Effect Enhancer" to Improve Cancer Nanomedicine Efficacy

Simple Summary

Electroporation-based therapies (reversible electroporation, irreversible electroporation, electrochemotherapy) are used for the selective treatment of deep-seated tumors. The combination of the structural modifications of the lipid bilayer of cell membranes, due to the application of electrical pulses in the targeted tissue, with the concomitant systemic (intravenous) administration of drugs can be considered as a sort of bridge between local-regional and systemic treatments. A possible further application of these techniques can be envisaged in their use as enhancers of the so-called “enhanced permeability and retention” effect. The intratumoral uptake of drug-loaded nanocarriers concomitant with the application of electric pulses in the target tumor is a new scenario worthy of attention and can represent a potential new frontier for drug delivery in oncology.

Abstract

Surgical resection is the gold standard for the treatment of many kinds of tumor, but its success depends on the early diagnosis and the absence of metastases. However, many deep-seated tumors (liver, pancreas, for example) are often unresectable at the time of diagnosis. Chemotherapies and radiotherapies are a second line for cancer treatment. The “enhanced permeability and retention” (EPR) effect is believed to play a fundamental role in the passive uptake of drug-loaded nanocarriers, for example polymeric nanoparticles, in deep-seated tumors. However, criticisms of the EPR effect were recently raised, particularly in advanced human cancers: obstructed blood vessels and suppressed blood flow determine a heterogeneity of the EPR effect, with negative consequences on nanocarrier accumulation, retention, and intratumoral distribution. Therefore, to improve the nanomedicine uptake, there is a strong need for “EPR enhancers”. Electrochemotherapy represents an important tool for the treatment of deep-seated tumors, usually combined with the systemic (intravenous) administration of anticancer drugs, such as bleomycin or cisplatin. A possible new strategy, worthy of investigation, could be the use of this technique as an “EPR enhancer” of a target tumor, combined with the intratumoral administration of drug-loaded nanoparticles. This is a general overview of the rational basis for which EP could be envisaged as an “EPR enhancer” in nanomedicine.

Electrotherapies for Glioblastoma

Non-thermal, intermediate frequency (100-500 kHz) electrotherapies present a unique therapeutic strategy to treat malignant neoplasms. Here, pulsed electric fields (PEFs) which induce reversible or irreversible electroporation (IRE) and tumour-treating fields (TTFs) are reviewed highlighting the foundations, advances, and considerations of each method when applied to glioblastoma (GBM). Several biological aspects of GBM that contribute to treatment complexity (heterogeneity, recurrence, resistance, and blood-brain barrier(BBB)) and electrophysiological traits which are suggested to promote glioma progression are described. Particularly, the biological responses at the cellular and molecular level to specific parameters of the electrical stimuli are discussed offering ways to compare these parameters despite the lack of a universally adopted physical description. Reviewing the literature, a disconnect is found between electrotherapy techniques and how they target the biological complexities of GBM that make treatment difficult in the first place. An attempt is made to bridge the interdisciplinary gap by mapping biological characteristics to different methods of electrotherapy, suggesting important future research topics and directions in both understanding and treating GBM. To the authors' knowledge, this is the first paper that attempts an in-tandem assessment of the biological effects of different aspects of intermediate frequency electrotherapy methods, thus offering possible strategies toward GBM treatment.

Local ablation of pancreatic tumors: State of the art and future perspectives

BACKGROUND

Currently, the technologies most commonly used to treat locally advanced pancreatic cancer are radiofrequency ablation (RFA), microwave ablation, and irreversible (IRE) or reversible electroporation combined with low doses of chemotherapeutic drugs.

AIM

To report an overview and updates on ablative techniques in pancreatic cancer.

METHODS

Several electronic databases were searched. The search covered the years from January 2000 to January 2021. Moreover, the reference lists of the found papers were analysed for papers not indexed in the electronic databases. All titles and abstracts were analysed.

RESULTS

We found 30 studies (14 studies for RFA, 3 for microwave therapy, 10 for IRE, and 3 for electrochemotherapy), comprising 1047 patients, which were analysed further. Two randomized trials were found for IRE. Percutaneous and laparotomy approaches were performed. In the assessed patients, the median maximal diameter of the lesions was in the range of 2.8 to 4.5 cm. All series included patients unfit for surgical treatment, but Martin et al assessed a subgroup of patients with borderline resectable tumours who underwent resection with margin attenuation with IRE. Most studies administered chemotherapy prior to ablative therapies. However, several studies suggest that the key determinant of improved survival is attributable to ablative treatment alone. Nevertheless, the authors suggested chemotherapy before local therapies for several reasons. This strategy may not only downstage a subgroup of patients to curative-intent surgery but also support to recognize patients with biologically unfavourable tumours who would likely not benefit from ablation treatments. Ablation therapies seem safe based on the 1047 patients assessed in this review. The mortality rate ranged from 1.8% to 2%. However, despite the low mortality, the reported rates of severe post procedural complications ranged from 0%-42%. Most reported complications have been self-limiting and manageable. Median overall survival varied between 6.0 and 33 mo. Regarding the technical success rate, assessed papers reported an estimated rate in the range of 85% to 100%. However, the authors reported early recurrence after treatment. A distinct consideration should be made on whether local treatments induce an immune response in the ablated area. Preclinical and clinical studies have shown that RFA is a promising mechanism for inducing antigen-presenting cell infiltration and enhancing the systemic antitumour T-cell immune response and tumour regression.

CONCLUSION

In the management of patients with pancreatic cancer, the possibility of a multimodal approach should be considered, and conceptually, the combination of RFA with immunotherapy represents a novel angle of attack against this tumour.

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.

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.

Ablation in Pancreatic Cancer: Past, Present and Future

The insidious onset and aggressive nature of pancreatic cancer contributes to the poor treatment response and high mortality of this devastating disease. While surgery, chemotherapy and radiation have contributed to improvements in overall survival, roughly 90% of those afflicted by this disease will die within 5 years of diagnosis. The developed ablative locoregional treatment modalities have demonstrated promise in terms of overall survival and quality of life. In this review, we discuss some of the recent studies demonstrating the safety and efficacy of ablative treatments in patients with locally advanced pancreatic cancer.

Irreversible Electroporation (IRE) in Locally Advanced Pancreatic Cancer: A Review of Current Clinical Outcomes, Mechanism of Action and Opportunities for Synergistic Therapy

Locally advanced pancreatic cancer (LAPC) accounts for 30% of patients with pancreatic cancer. Irreversible electroporation (IRE) is a novel cancer treatment that may improve survival and quality of life in LAPC. This narrative review will provide a perspective on the clinical experience of pancreas IRE therapy, explore the evidence for the mode of action, assess treatment complications, and propose strategies for augmenting IRE response. A systematic search was performed using PubMed regarding the clinical use and safety profile of IRE on pancreatic cancer, post-IRE sequential histological changes, associated immune response, and synergistic therapies. Animal data demonstrate that IRE induces both apoptosis and necrosis followed by fibrosis. Major complications may result from IRE; procedure related mortality is up to 2%, with an average morbidity as high as 36%. Nevertheless, prospective and retrospective studies suggest that IRE treatment may increase median overall survival of LAPC to as much as 30 months and provide preliminary data justifying the well-designed trials currently underway, comparing IRE to the standard of care treatment. The mechanism of action of IRE remains unknown, and there is a lack of data on treatment variables and efficiency in humans. There is emerging data suggesting that IRE can be augmented with synergistic therapies such as immunotherapy.

Irreversible electroporation ablation overcomes tumor-associated immunosuppression to improve the efficacy of DC vaccination in a mice model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is associated with highly immunosuppressive tumor microenvironment (TME) that can limit the efficacy of dendritic cell (DC) vaccine immunotherapy. Irreversible electroporation (IRE) is a local ablation approach. Herein, we test the hypothesis that IRE ablation can overcome TME immunosuppression to improve the efficacy of DC vaccination using Kras^LSL-G12D-p53^LSL-R172H-Pdx-1-Cre (KPC) orthotopic mouse model of PDAC. The median survival for mice treated with the combined IRE and DC vaccination was 77 days compared with sham control (35 days), DC vaccination (49 days), and IRE (44 days) groups (P = .006). Thirty-six percent of the mice treated with combination IRE and DC vaccination were still survival at the end of the study period (90 days) without visible tumor. The changes of tumor apparent diffusion coefficient (ΔADC) were higher in mice treated with combination IRE and DC vaccination than that of other groups (all P < .001); tumor ΔADC value positively correlated with tumor fibrosis fraction (R = 0.707, P < .001). IRE induced immunogenic cell death and alleviation of immunosuppressive components in PDAC TME when combined with DC vaccination, including increased tumor infiltration of CD8⁺ T cells and Granzyme B⁺ cells (P = .001, and P = .007, respectively). Our data show that IRE ablation can overcome TME immunosuppression to improve the efficacy of DC vaccination in PDAC. Combination IRE ablation and DC vaccination may enhance therapeutic efficacy for PDAC.

Assessment of Ablation Therapy in Pancreatic Cancer: The Radiologist's Challenge

This article provides an overview of imaging assessment of ablated pancreatic cancer. Only studies reporting radiological assessment on pancreatic ablated cancer were retained. We found 16 clinical studies that satisfied the inclusion criteria. Radiofrequency ablation and irreversible electroporation have become established treatment modalities because of their efficacy, low complication rates, and availability. Microwave Ablation (MWA) has several advantages over radiofrequency ablation (RFA), which may make it more attractive to treat pancreatic cancer. Electrochemotherapy (ECT) is a very interesting emerging technique, characterized by low complication rate and safety profile. According to the literature, the assessment of the effectiveness of ablative therapies is difficult by means of the Response Evaluation Criteria in Solid Tumors (RECIST) criteria that are not suitable to evaluate the treatment response considering that are related to technique used, the timing of reassessment, and the imaging procedure being used to evaluate the efficacy. RFA causes various appearances on imaging in the ablated zone, correlating to the different effects, such as interstitial edema, hemorrhage, carbonization, necrosis, and fibrosis. Irreversible electroporation (IRE) causes the creation of pores within the cell membrane causing cell death. Experimental studies showed that Diffusion Weigthed Imaging (DWI) extracted parameters could be used to detect therapy effects. No data about functional assessment post MWA is available in literature. Morphologic data extracted by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) do not allow to differentiate partial, complete, or incomplete response after ECT conversely to functional parameters, obtained with Position Emission Tomography (PET), MRI, and CT.

Analysis of damage-associated molecular pattern molecules due to electroporation of cells in vitro

Background Tumor cells can die via immunogenic cell death pathway, in which damage-associated molecular pattern molecules (DAMPs) are released from the cells. These molecules activate cells involved in the immune response. Both innate and adaptive immune response can be activated, causing a destruction of the remaining infected cells. Activation of immune response is also an important component of tumor treatment with electrochemotherapy (ECT) and irreversible electroporation (IRE). We thus explored, if and when specific DAMPs are released as a consequence of electroporation in vitro. Materials and methods In this in vitro study, 100 μs long electric pulses were applied to a suspension of Chinese hamster ovary cells. The release of DAMPs - specifically: adenosine triphosphate (ATP), calreticulin, nucleic acids and uric acid was investigated at different time points after exposing the cells to electric pulses of different amplitudes. The release of DAMPs was statistically correlated with cell permeabilization and cell survival, e.g. reversible and irreversible electroporation. Results In general, the release of DAMPs increases with increasing pulse amplitude. Concentration of DAMPs depend on the time interval between exposure of the cells to pulses and the analysis. Concentrations of most DAMPs correlate strongly with cell death. However, we detected no uric acid in the investigated samples. Conclusions Release of DAMPs can serve as a marker for prediction of cell death. Since the stability of certain DAMPs is time dependent, this should be considered when designing protocols for detecting DAMPs after electric pulse treatment.

Ultrastructural changes in hepatocellular carcinoma cells induced by exponential pulses of nanosecond duration delivered via a transmission line

Clinical applications of high-intensity pulsed electric fields have proven useful in ablating solid tumors. However, novel ideas for the development of an effective tumor ablation device are urgently needed. Here, we studied cellular effects of the nanosecond exponential pulse, which is generated by a capacitor-discharging circuit and delivered via a transmission line. Pulses of peak voltage boosted by transmission line oscillation possess high capability to induce swelling and to cause loss of viability in cells. The appropriate parameter of the pulse was selected to investigate the ultrastructural changes in swollen cells, which present smoothened plasma membrane, loss of microvilli, and lowered cytoplasm electron density. We propose the equivalent force field hypothesis to understand the mechanism underlying cell swelling induced by pulsing. Wrinkles on the plasma membrane might indicate recovery from cell swelling, and this was verified by co-culture of pulsed PKH26-Cells with sham-treated PKH67-Cells. We concluded that the ultrastructural changes, such as irregular pores formed on the plasma membrane, were mainly induced by the effect of electric pulse applied on the charged molecules in the membrane.

Dynamics of Cell Death After Conventional IRE and H-FIRE Treatments

High-frequency irreversible electroporation (H-FIRE) has emerged as an alternative to conventional irreversible electroporation (IRE) to overcome the issues associated with neuromuscular electrical stimulation that appear in IRE treatments. In H-FIRE, the monopolar pulses typically used in IRE are replaced with bursts of short bipolar pulses. Currently, very little is known regarding how the use of a different waveform affects the cell death dynamics and mechanisms. In this study, human pancreatic adenocarcinoma cells were treated with a typical IRE protocol and various H-FIRE schemes with the same energized time. Cell viability, membrane integrity and Caspase 3/7 activity were assessed at different times after the treatment. In both treatments, we identified two different death dynamics (immediate and delayed) and we quantified the electric field ranges that lead to each of them. While in the typical IRE protocol, the electric field range leading to a delayed cell death is very narrow, this range is wider in H-FIRE and can be increased by reducing the pulse length. Membrane integrity in cells suffering a delayed cell death shows a similar time evolution in all treatments, however, Caspase 3/7 expression was only observed in cells treated with H-FIRE.

Intraoperative Irreversible Electroporation in Locally Advanced Pancreatic Cancer: A Guide for the Interventional Radiologist

Efforts to improve mortality associated with locally advanced pancreatic cancer (LAPC) have shown minimal gains despite advances in surgical technique, systemic treatments, and radiation therapy. Locoregional therapy with ablation has not been routinely adopted due to the high risk of complications associated with thermal destruction of the pancreas. Irreversible electroporation (IRE) is an emerging, nonthermal, ablative technology that has demonstrated the ability to generate controlled ablation of LAPC while preserving pancreatic parenchymal integrity. IRE may be performed percutaneously or via laparotomy and will commonly involve multidisciplinary treatment teams. This article will describe the technical aspects of how multidisciplinary IRE is performed during laparotomy at a single tertiary care institution.

Electroporation-induced changes in tumor vasculature and microenvironment can promote the delivery and increase the efficacy of sorafenib nanoparticles

Blood vessels, the extracellular space, and the cell membrane represent physiologic barriers to nanoparticle-based drug delivery for cancer therapy. We demonstrate that electroporation (EP) can assist in the delivery of dye stabilized sorafenib nanoparticles (SFB-IR783) by increasing the permeability of endothelial monolayers, improving diffusion through the extracellular space in tumorspheres, and by disrupting plasma membrane function in cancer cells. These changes occur in a dose-dependent fashion, increasing proportionally with electric field strength. Cell death from irreversible electroporation (IRE) was observed to contribute to the persistent transport of SFB-IR783 through these physiologic barriers. In a model of mice bearing bilateral xenograft HCT116 colorectal tumors, treatment with EP resulted in the immediate and increased uptake of SFB-IR783 when compared with the untreated contralateral tumor. The uptake of SFB-IR783 was independent of direct transfection of cells through EP and was mediated by changes in vascular permeability and extracellular diffusion. The combination of EP and SFB-IR783 was observed to result in 40% reduction in mean tumor diameter when compared with sham treatment (p < .05) at the time of sacrifice, which was not observed in cohorts treated with EP alone or SFB-IR783 alone. Treatment of tumor with EP can augment the uptake and increase the efficacy of nanoparticle therapy.

High-frequency irreversible electroporation is an effective tumor ablation strategy that induces immunologic cell death and promotes systemic anti-tumor immunity

Background

Despite promising treatments for breast cancer, mortality rates remain high and treatments for metastatic disease are limited. High-frequency irreversible electroporation (H-FIRE) is a novel tumor ablation technique that utilizes high-frequency bipolar electric pulses to destabilize cancer cell membranes and induce cell death. However, there is currently a paucity of data pertaining to immune system activation following H-FIRE and other electroporation based tumor ablation techniques.

Methods

Here, we utilized the mouse 4T1 mammary tumor model to evaluate H-FIRE treatment parameters on cancer progression and immune system activation in vitro and in vivo.

Findings

H-FIRE effectively ablates the primary tumor and induces a pro-inflammatory shift in the tumor microenvironment. We further show that local treatment with H-FIRE significantly reduces 4T1 metastases. H-FIRE kills 4T1 cells through non-thermal mechanisms associated with necrosis and pyroptosis resulting in damage associated molecular pattern signaling in vitro and in vivo. Our data indicate that the level of tumor ablation correlates with increased activation of cellular immunity. Likewise, we show that the decrease in metastatic lesions is dependent on the intact immune system and H-FIRE generates 4T1 neoantigens that engage the adaptive immune system to significantly attenuate tumor progression.

Interpretation

Cell death and tumor ablation following H-FIRE treatment activates the local innate immune system, which shifts the tumor microenvironment from an anti-inflammatory state to a pro-inflammatory state. The non-thermal damage to the cancer cells and increased innate immune system stimulation improves antigen presentation, resulting in the engagement of the adaptive immune system and improved systemic anti-tumor immunity.

Palliative therapy in pancreatic cancer-interventional treatment with radiofrequency ablation/irreversible electroporation

Pancreatic cancer (PC) is a solid tumor with still a dismal prognosis. Diagnosis is usually late, when the disease is metastatic or locally advanced (LAPC). Only 20% of PC are amenable to surgery at the time of diagnosis and the vast majority of them, despite radically resected will unavoidably recur. The treatment of LAPC is a challenge. Current guidelines suggest to adopt systemic therapies upfront, based on multi-drugs chemotherapy regimens. However, the vast majority of patients will never experience conversion to surgical exploration and radical resection. Thus, there a large subgroup of LAPC patients where the only therapeutic chance is to offer palliative treatments, such as interventional ablative treatments, in order to obtain a cytoreduction of the tumor, trying to delay its growth and spread. Radiofrequency ablation (RFA) and irreversible electroporation (IRE) demonstrated to be safe and effective in obtaining a local control of the disease with some promising oncological results in terms of overall survival (OS). However, they should be adopted as a treatment strategy to adopt in parallel with other systemic therapies, within multidisciplinary choices. They are not free from complications, even serious, thus they should applied only in specialized centers of pancreatology. This review depicts the state of the art of the two techniques.

Diffusion MRI biomarkers predict the outcome of irreversible electroporation in a pancreatic tumor mouse model

The purpose of this work is to explore the potential contribution of diffusion MRI to predict the effects of irreversible electroporation (IRE) in a pancreatic ductal adenocarcinoma (PDAC) mouse model. Thirteen mice were injected with Panc-02 PDAC cells in both flanks. One tumor was treated with IRE when it reached a diameter of about 5 mm. T2- and diffusion-weighted MRI sequences were acquired before IRE treatment and 1, 3 and 7 days later. The mice were euthanized 1 day (n = 6) or 2 weeks (n = 7) after treatment. The tumors were excised and stained with H&E, caspase-3, CD-3, F4/80. The volume and the mean and standard deviation of the apparent diffusion coefficient (ADC) were compared between treated and untreated lesions and correlated with histology-derived measures. At 1-day post-treatment, a dramatic ADC increase (+50.81%, P < 0.05) was found in ablated lesions, strongly correlated with apoptosis (τ = 0.90). At later time points the ADC returned to pre-treatment values, though histopathology showed a quite different scenario compared to the untreated controls. The ADC standard deviation measured within the treated tumors 1 day after IRE treatment had a strong negative correlation with the number of tumor cells found 14 days later (τ = 0.80). There was also a strong correlation between 1-day ADC and 14-day apoptosis in untreated tumors (τ = 0.95). In conclusion, diffusion MRI is sensitive to the short-term effects of IRE in PDAC tumors, and can help predict the long-term treatment outcome.

High-voltage pulsed electric field plus photodynamic therapy kills breast cancer cells by triggering apoptosis

This study evaluated the effects and mechanism of action of combining irreversible electroporation (IRE) and photodynamic therapy (PDT) in breast cancer cells in vitro and in vivo. Jin's formula was used to assess killing efficacy of different IRE+PDT dosing combinations in breast cancer MCF-7 cells. Flow cytometry, high-content imaging, and confocal laser scanning microscopy were used to detect apoptosis. qRT-PCR and western blotting were used to evaluate expression of apoptosis-related genes and proteins. IRE+PDT combination therapy was administered to BALB/C mice with breast cancer tumors in vivo; tumor size was used to assess treatment efficacy. Killing mechanisms were examined using transmission electron microscopy and immunohistochemistry. We found that IRE+PDT combination therapy produced significant synergistic killing effects in breast cancer cells (highest Jin q value of 1.32). Early apoptosis rates were significantly higher in the IRE+PDT group (16.0%) than in IRE-alone (7.6%) and PDT-alone (4.6%) groups (P<0.05). qRT-PCR showed higher Caspase-1, -3, -5, -6, -7, -8, and -9 and TNFRSF1A expression with IRE+PDT than with control. Western blots showed increased cleaved Caspase-3, -7, and -9, and PARP levels in the IRE+PDT group. In vivo tumor suppression rate for IRE (1200 V)+PDT (10 mg/kg) was 68.3%. Combination therapy produced the most obvious apoptosis effects. Compared with controls, the IRE+PDT group exhibited lower new blood vessel (VEGF, CD31), metastasis (TGF-β), and cell proliferation (Ki-67) indicators and higher inflammation indicator (TNF-α) 1 day post-treatment. Thus, combining IRE and PDT enhanced their anti-tumor effects in breast cancer, and apoptosis played a key role in this process.

Irreversible electroporation of pancreatic adenocarcinoma: a primer for the radiologist

Irreversible electroporation (IRE) is increasingly used for the ablation of unresectable locally advanced pancreatic adenocarcinoma. Unlike other ablation technologies that cannot be safely used around critical vasculature or ducts for risk of thermal damage, IRE uses high-voltage pulses to disrupt cellular membranes. This causes cell death by apoptosis and inflammation. IRE has been deployed by both open and percutaneous approaches. Generator parameters are the same for both approaches, and settings are pancreas specific. Variations in settings, probe placement, and probe exposure can result in thermal damage or reversible electroporation and resultant treatment failure, morbidity, or mortality. When used properly, IRE appears to improve overall survival and local recurrence, but does not influence the rate of distant recurrence. However, studies of both open and percutaneous approaches have been relatively small, non-controlled, and without appropriate comparisons. It is challenging for the radiologist to interpret treatment effects after IRE because of a dearth of guiding literature and pathologic correlates. This primer describes technical aspects, pathology correlates, post-IRE imaging, and outcomes for percutaneous and open approaches.

Reversible Electroporation-Mediated Liposomal Doxorubicin Delivery to Tumors Can Be Monitored With 89Zr-Labeled Reporter Nanoparticles

Reversible electroporation (RE) can facilitate nanoparticle delivery to tumors through direct transfection and from changes in vascular permeability. We investigated a radiolabeled liposomal nanoparticle (89Zr-NRep) for monitoring RE-mediated liposomal doxorubicin (DOX) delivery in mouse tumors. Intravenously delivered 89Zr-NRep allowed positron emission tomography imaging of electroporation-mediated nanoparticle uptake. The relative order of 89Zr-NRep injection and electroporation did not result in significantly different overall tumor uptake, suggesting direct transfection and vascular permeability can independently mediate deposition of 89Zr-NRep in tumors. 89Zr-NRep and DOX uptake correlated well in both electroporated and control tumors at all experimental time points. Electroporation accelerated 89Zr-NRep and DOX deposition into tumors and increased DOX dosing. Reversible electroporation-related vascular effects seem to play an important role in nanoparticle delivery to tumors and drug uptake can be quantified with 89Zr-NRep.

18F-FDG PET Biomarkers Help Detect Early Metabolic Response to Irreversible Electroporation and Predict Therapeutic Outcomes in a Rat Liver Tumor Model

Purpose To test the hypothesis that biomarkers of fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography (PET) can be used for the early detection of therapeutic response to irreversible electroporation (IRE) of liver tumor in a rodent liver tumor model. Materials and Methods The institutional animal care and use committee approved this study. Rats were inoculated with McA-RH7777 liver tumor cells in the left median and left lateral lobes. Tumors were allowed to grow for 7 days to reach a size typically at least 5 mm in longest diameter, as verified with magnetic resonance (MR) imaging. IRE electrodes were inserted, and eight 100-μsec, 2000-V pulses were applied to ablate the tumor tissue in the left median lobe. Tumor in the left lateral lobe served as a control in each animal. PET/computed tomography (CT) and MR imaging measurements were performed at baseline and 3 days after IRE for each animal. Additional MR imaging measurements were obtained 14 days after IRE. After 14-day follow-up MR imaging, rats were euthanized and tumors harvested for hematoxylin-eosin, CD34, and caspase-3 staining. Change in the maximum standardized uptake value (ΔSUV_max) was calculated 3 days after IRE. The maximum lesion diameter change (ΔD_max) was measured 14 days after IRE by using axial T2-weighted imaging. ΔSUV_max and ΔD_max were compared. The apoptosis index was calculated by using caspase-3-stained slices of apoptotic tumor cells. Pearson correlation coefficients were calculated to assess the relationship between ΔSUV_max at 3 days and ΔD_max (or apoptosis index) at 14 days after IRE treatment. Results ΔSUV_max, ΔD_max, and apoptosis index significantly differed between treated and untreated tumors (P < .001 for all). In treated tumors, there was a strong correlation between ΔSUV_max 3 days after IRE and ΔD_max 14 days after IRE (R = 0.66, P = .01) and between ΔSUV_max 3 days after IRE and apoptosis index 14 days after IRE (R = 0.57, P = .04). Conclusion ¹⁸F-FDG PET imaging biomarkers can be used for the early detection of therapeutic response to IRE treatment of liver tumors in a rodent model. ^© RSNA, 2017.

Breast tissue ablation with irreversible electroporation in rabbits: A safety and feasibility study

Background and aim

Irreversible electroporation (IRE) was confirmed to control several solid tumors effectively in vivo. Our preclinical study aimed to assess the feasibility and safety of IRE in the breast of rabbit.

Methods

Thirty New Zealand white rabbits were randomly divided into 3 groups of 10 rabbits (control group, IRE group A, and B). Two mono-electrode needles were inserted into the breast tissue by percutaneous puncture. Electrocardiogram and vital signs were monitored before, during, and after ablation. Histopathology, immunohistochemistry, and transmission electron microscopy were examined at 0 hours, 12 hours, 24 hours, 4 days, 7 days, 14 days, and 28 days after ablation.

Results

All the rabbits survived the procedure with no significant adverse effects. Intra-operative ventricular arrhythmias occurred in 1 rabbit from IRE group B and was immediately relieved after ablation. Reversible subcutaneous hemorrhage was observed in 8 rabbits from IRE group A and 7 rabbits from IRE group B. No skin was burnt, however, pectoralis major muscle injuries were found in all rabbits. Histopathological and ultrastructural examination revealed the coexistence of cell necrosis and apoptosis. HE, TUNEL, and Masson staining revealed breast tissue injury and the recovery of damage by fibrous tissue and granulation tissue. Notably, the structures of mammary gland lobules and interstitial components of the breasts were well preserved.

Conclusions

Our study suggests that IRE destroys breast cancer while effectively preserving the skin, the structure of mammary gland lobules, and interstitial components. IRE may be a promising technique to locally control breast cancer and to maintain the esthetic of the breast.

Irreversible Electroporation for Locally Advanced Pancreatic Cancer: Where Do We Stand in 2017?

Pancreatic adenocarcinoma has a very poor prognosis. Complete surgical resection remains the only current curative treatment. Locally advanced pancreatic cancers are considered as unresectable because of involvement of celiac and/or mesenteric vessels. Irreversible electroporation has recently been introduced to induce permanent cell death by apoptosis. Irreversible electroporation is a nonthermal cell-destruction technique that was claimed to allow destruction of cancerous cells with less damage to surrounding supporting connective tissues with collagenic structure (such as nearby blood vessels, biliary ducts, and nerves) than other types of treatment. Applications on pancreatic adenocarcinoma seem promising, and this article is an up-to-date review of the first results.

Pain Analysis in Patients with Pancreatic Carcinoma: Irreversible Electroporation versus Cryoablation

The aim of this article is to evaluate and compare the postprocedure pain in patients with pancreatic carcinoma treated with irreversible electroporation (IRE) and cryoablation (CRYO). We compared 22 patients with 22 lesions in pancreas treated with IRE and 26 patients with 27 lesions treated with cryosurgery. All the patients in the two groups were under celiac plexus block (CPB) treatment to alleviate the postprocedure pain. A numerical rating scale (VAS) consisting of 11-point scales and the 24 h total hydromorphone use were recorded for the analysis of the pain level in the patients who underwent these two technologies separately. Other parameters, such as the complications and the ECOG performance status, were also noted. Statistical analysis was performed by Fisher's exact test, the Chi-square test, and Student's t-test. All the pancreatic carcinoma patients in our study were reported to have postprocedure pain in the two groups. But there was no significant difference in the mean pain score (4.95 (IRE) versus 4.85 (CRYO); P = 0.52) and 24 h total hydromorphone use (3.89 mg (IRE) versus 3.97 mg (CRYO); P = 0.30). IRE is comparable to cryotherapy in the amount of pain that patients with pancreatic carcinoma experience.

Percutaneous ablation of pancreatic cancer

Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review.

Therapy Monitoring with Functional and Molecular MR Imaging

Cancer therapy is mainly based on different combinations of surgery, radiotherapy, and chemotherapy. Additionally, targeted therapies (designed to disrupt specific tumor hallmarks, such as angiogenesis, metabolism, proliferation, invasiveness, and immune evasion), hormonotherapy, immunotherapy, and interventional techniques have emerged as alternative oncologic treatments. Conventional imaging techniques and current response criteria do not always provide the necessary information regarding therapy success particularly to targeted therapies. In this setting, MR imaging offers an attractive combination of anatomic, physiologic, and molecular information, which may surpass these limitations, and is being increasingly used for therapy response assessment.

Irreversible Electroporation as an Effective Technique for Ablating Human Metastatic Osteosarcoma

Irreversible electroporation (IRE) induces apoptosis in tumor cells with electric energy, allowing treatment of unresectable tumors. One potential application is metastatic osteosarcoma (OS) in the pediatric population. A 12-year-old underwent thoracotomy with resection of metastatic OS. IRE was applied to 1 resected tumor section. Using 2 probes, 100 pulses with width of 90 ms were delivered. Efficacy was measured by increase in current draw during treatment. The treated sample was analyzed with hematoxylin and eosin and transmission electron microscopy. Default voltage of 1800 kV was ineffective. Voltage of 2700 kV caused excessive current draw and was aborted to prevent thermal injury. At 2200 kV, current draw rise was 9 amps, signifying successful treatment. Untreated specimen showed viable OS, normal surrounding lung tissue. Treated tumor had edema within the tumor and in surrounding lung tissue, with intra-alveolar hemorrhage and cellular architecture destruction. There was also evidence for cellular destruction such as disruption of lipid bilayer and release of intracellular fluid. Optimal voltage for treatment was 2200 kV, likely higher due to electrical conduction variation in the aerated lung. IRE may be an option for pediatric patients with unresectable metastatic OS.

Low temperature plasmas as emerging cancer therapeutics: the state of play and thoughts for the future

The field of plasma medicine has seen substantial advances over the last decade, with applications developed for bacterial sterilisation, wound healing and cancer treatment. Low temperature plasmas (LTPs) are particularly suited for medical purposes since they are operated in the laboratory at atmospheric pressure and room temperature, providing a rich source of reactive oxygen and nitrogen species (RONS). A great deal of research has been conducted into the role of reactive species in both the growth and treatment of cancer, where long-established radio- and chemo-therapies exploit their ability to induce potent cytopathic effects. In addition to producing a plethora of RONS, LTPs can also create strong electroporative fields. From an application perspective, it has been shown that LTPs can be applied precisely to a small target area. On this basis, LTPs have been proposed as a promising future strategy to accurately and effectively control and eradicate tumours. This review aims to evaluate the current state of the literature in the field of plasma oncology and highlight the potential for the use of LTPs in combination therapy. We also present novel data on the effect of LTPs on cancer stem cells, and speculatively outline how LTPs could circumvent treatment resistance encountered with existing therapeutics.

Local Ablative Strategies for Ductal Pancreatic Cancer (Radiofrequency Ablation, Irreversible Electroporation): A Review

Pancreatic ductal adenocarcinoma (PDAC) has still a dismal prognosis. Locally advanced pancreatic cancer (LAPC) accounts for the 40% of the new diagnoses. Current treatment options are based on chemo- and radiotherapy regimens. Local ablative techniques seem to be the future therapeutic option for stage-III patients with PDAC. Radiofrequency Ablation (RFA) and Irreversible Electroporation (IRE) are actually the most emerging local ablative techniques used on LAPC. Initial clinical studies on the use of these techniques have already demonstrated encouraging results in terms of safety and feasibility. Unfortunately, few studies on their efficacy are currently available. Even though some reports on the overall survival are encouraging, randomized studies are still required to corroborate these findings. This study provides an up-to-date overview and a thematic summary of the current available evidence on the application of RFA and IRE on PDAC, together with a comparison of the two procedures.

Irreversible electroporation of the pancreas is feasible and safe in a porcine survival model

OBJECTIVES

Use of thermal tumor ablation in the pancreatic parenchyma is limited because of the risk of pancreatitis, pancreatic fistula, or hemorrhage. This study aimed to evaluate the feasibility and safety of irreversible electroporation (IRE) in a porcine model.

METHODS

Ten pigs were divided into 2 study groups. In the first group, animals received IRE of the pancreatic tail and were killed after 60 minutes. In the second group, animals received IRE at the head of the pancreas and were followed up for 7 days. Clinical parameters, computed tomography imaging, laboratory results, and histology were obtained.

RESULTS

All animals survived IRE ablation, and no cardiac adverse effects were noted. Sixty minutes after IRE, a hypodense lesion on computed tomography imaging indicated the ablation zone. None of the animals developed clinical signs of acute pancreatitis. Only small amounts of ascites fluid, with a transient increase in amylase and lipase levels, were observed, indicating that no pancreatic fistula occurred.

CONCLUSIONS

This porcine model shows that IRE is feasible and safe in the pancreatic parenchyma. Computed tomography imaging reveals significant changes at 60 minutes after IRE and therefore might serve as an early indicator of therapeutic success. Clinical studies are needed to evaluate the efficacy of IRE in pancreatic cancer.

Addition of pluronics® to reducible disulfide-bond-containing Pluronic®-PEI-SS specifically enhances circulation time in vivo and transfection efficiency in vitro

To improve the circulation time and transfection efficiency of the polyplexes used in gene delivery, a series of Pluronic®/Pluronic®F127-PEI-SS/pDNA complexes (PFPS/pDNA), based on the addition of different kinds of Pluronics® to the reducible disulfide-bonds-containing Pluronic®F127-PEI-SS/pDNA (FPS/pDNA) polyplexes, was prepared and evaluated in Bcap and Hela cells in vitro and in vivo. The addition of Pluronics® with molecular weights and hydrophilic-lipophilic balance (HLBs) different from that in the FPS/pDNA complex resulted in five PFPS(1-5)/pDNA complexes, and the correlation between the structure of the free Pluronic® and the properties of the PFPS/pDNA complexes was investigated. The addition of Pluronics® resulted in slightly larger or same-sized nanoparticles of PFPS/pDNA at a constant N/P ratio. The PFPS copolymer displayed strong stability against DNase I digestion and serum degradation. PFPS-4 containing added Pluronic® L35, with an intermediate HLB of 19, showed a much higher transfection efficiency and less cytotoxicity than FPS or PEI-25 kDa in vitro. PFPS-4 also exhibited a considerably longer blood circulation time than FPS or PEI-25 kDa in vivo in mice, indicating that the addition of an intermediate Pluronic® can enhance the transfection efficiency of gene delivery systems.