Electrochemotherapy and immune interactions; A boost to the system?

New effective and less painful high frequency electrochemotherapy protocols: From optimization on 3D models to pilot study on veterinary patients

Electroporation, a physical method that permeabilizes cell membranes, is increasingly used in cancer treatment. By enhancing the uptake of hydrophilic antitumor drugs, it boosts their cytotoxic effects and has proven effective in both human and veterinary medicine through electrochemotherapy. However, this treatment requires loco-regional or even general anesthesia, as electrical pulses cause muscle contractions and pain. Several clinical studies have demonstrated that application of high frequency pulses (above 5000 Hz) and short pulse duration (under 11 μs) causes much less discomfort to patients. In order to reduce the pain associated with contractions while maintaining the effectiveness of the treatment, we have developed new protocols using a high-frequency generator that delivers electric field pulses at a pulse repetition rate up to 2 MHz, associated to a multipolar electrode. In vitro tests on colorectal cancer cells were performed to assess the efficiency of cisplatin and bleomycin in inducing cell death. The efficiency obtained after one single treatment on both cell suspensions and on 3D multicellular spheroid models were similar to the ones obtained using ESOPE (European standard operating procedures for electrochemotherapy) protocol, which is currently used in clinics. In addition, as tumor cells die in an immunogenic cell death (ICD) mode and can release danger associated molecular patterns (DAMPs), major hallmarks of ICD were evaluated following the treatment by quantifying the apoptotic cell death, caspases 3/7 activation and key DAMPs. Subsequently, pilot studies on small number of conscious cats and horses under mild sedation confirmed that these protocols did not cause any noticeable muscle contractions and resulted in either partial or complete responses. New high-frequency electroporation protocols, described herein, show great promise in shifting electrochemotherapy into an effective and painless cancer treatment.

[Position Paper of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) and the German Roentgen Society (DRG) on Structural and Professional Requirements in Interventional Oncology]

Interventional oncology (IO) employs various techniques to enable minimally invasive, image-guided treatment of tumor diseases with both curative and palliative goals. Additionally, it significantly contributes to managing tumor-related and perioperative complications, offering diverse supportive procedures for patients at all stages of their diseases. The execution of IO procedures places unique demands on the equipment, personnel, and structural organization of radiological clinics, necessitating specific expertise from interventional radiologists.This position paper aims to comprehensively outline the multifaceted aspects of IO and discuss the requisite criteria for hospitals, radiological clinics, and interventional radiologists (IRs). Furthermore, it underscores overarching considerations of quality assurance that clinics and professional societies should prioritize.The requirements for hospitals, radiological clinics, and IRs are varied and demand not only a high level of proficiency in performing IO procedures but also in-depth knowledge of the differential therapy for various tumor diseases. This expertise is essential for effectively serving as clinical partners in the interdisciplinary treatment of oncologic patients. Additionally, a thorough understanding and safe handling of ionizing radiation technologies, along with proficiency in radiation protection methods, which are fundamental aspects of radiological specialist training, is crucial for ensuring the safety of IO procedures for both patients and staff. The Deutsche Gesellschaft für Interventionelle Radiologie und minimal-invasive Therapie (DeGIR) and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) have long-established dedicated quality management programs, accrediting radiology clinics and certifying IRs. These initiatives aim to uphold the highest standards of care and meet the quality expectations set by politics in healthcare system, particularly in the realm of interventional radiology. · The various procedures in the field of interventional oncology (IO) are complex medical interventions that require not only the most advanced technical equipment but also adequate human resources, particularly specialized expertise in interventional radiology, diagnostic imaging, oncology, and radiation protection.. · This expertise is an integral part of the specialized medical training in radiology and is certified by professional societies such as the German Society for Interventional Radiology (DeGIR) and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE).. · Professional societies like DeGIR, CIRSE, and the American Society of Interventional Radiology (SIR) establish the necessary quality assurance framework for comprehensive, high-quality IO therapy through quality assurance (QA) registries, standard operating procedure (SOP) documents, and participation in guideline development.. · Currently, radiology is the only discipline that provides physicians with the theoretical and practical knowledge, skills, and competencies required to perform the demanding procedures in the field of IO through specialized training programs and tailored certification processes.. · Isfort P, Sommer CM, Bruners P et al. Position Paper of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) and the German Roentgen Society (DRG) on Structural and Professional Requirements in Interventional Oncology. Rofo 2025; 197: 546-556.

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.

Electrochemotherapy with bleomycin, oxaliplatin, or cisplatin in mouse tumor models, from tumor ablation to in situ vaccination

Introduction

In addition to its direct cytotoxic effects, ablative therapies as electrochemotherapy (ECT) can elicit indirect antitumor effects by triggering immune system responses. Here, we comprehensively analyzed this dual effectiveness of intratumoral ECT with chemotherapeutic drugs bleomycin (BLM), oxaliplatin (OXA), and cisplatin (CDDP). Our aim was to determine if ECT can act as in situ vaccination and thereby induce an abscopal effect. By evaluating ECT's potential for in situ vaccination, our goal was to pave the way for future advancements for its combination with emerging (immuno)therapies, leading to enhanced responses and outcomes.

Methods

We employed two mouse tumor models, the immunologically cold B16F10 melanoma and 4T1 mammary carcinoma, to explore both local and systemic (i.e., abscopal) antitumor effects following equieffective intratumoral ECT with BLM, OXA, and CDDP. Through histological analyses and the use of immunodeficient and metastatic (for abscopal effect) mouse models, we identified and compared both the cytotoxic and immunological components of ECT's antitumor efficiency, such as immunologically recognizable cell deaths (immunogenic cell death and necrosis) and immune infiltrate (CD11+, CD4+, CD8+, GrB+).

Results

Differences in immunological involvement after equieffective intratumoral ECT were highlighted by variable kinetics of immunologically recognizable cell deaths and immune infiltrate across the studied tumor models. Particularly, the 4T1 tumor model exhibited a more pronounced involvement of the immune component compared to the B16F10 tumor model. Variances in the antitumor (immune) response were also detected based on the chemotherapeutic drug used in ECT. Collectively, ECT demonstrated effectiveness in inducing in situ vaccination in both tumor models; however, an abscopal effect was observed in the 4T1 tumor model only.

Conclusions

This is the first preclinical study systematically comparing the immune involvement in intratumoral ECT's efficiency using three distinct chemotherapeutic drugs in mouse tumor models. The demonstrated variability in immune response to ECT across different tumor models and chemotherapeutic drugs provides a basis for future investigations aimed at enhancing the effectiveness of combined treatments.

Treatment strategies with electrochemotherapy for limb in-transit melanoma: Real-world outcomes from a European, retrospective, cohort study

BACKGROUND

This study analysed treatment strategies with electrochemotherapy (ECT) in melanoma with limb in-transit metastases (ITM).

METHODS

We audited AJCC v.8 stage IIIB-IIID patients treated across 22 centres (2006-2020) within the International Network for Sharing Practices of ECT (InspECT).

RESULTS

452 patients were included, 58 % pre-treated (93 % had lower limb ITM, 44 % had ≤10 metastases [median size 1.5 cm]. Treatment strategies included first-line ECT (n = 145, 32 %), ECT with concurrent locoregional/systemic treatment (n = 163, 36 %), and salvage ECT (n = 144, 32 %). The objective response rate was 63 % (complete response [CR], 24 %), increasing to 74 % (CR, 39 %) following retreatment (median two ECT, range 1-8). CR rate in treatment-naïve and pre-treated patients was 50 % vs 32 % (p < 0.001). Bleomycin de-escalation was associated with lower CR (p = 0.004). Small tumour number and size, hexagonal electrode, retreatment, and post-ECT skin ulceration predicted response in multivariable analysis. At a median follow-up of 61 months, local and locoregional recurrence occurred in 55 % and 81 % of patients. Median local progression-free, new lesions-free, and regional recurrence-free survival were 32.9, 6.9, and 7.7 months. Grade-3 toxicity was 15 %. Concurrent treatment and CR correlated with improved regional control and survival. Concomitant checkpoint inhibition did not impact toxicity or survival outcomes. The median overall survival was 5.7 years.

CONCLUSIONS

Among patients with low-burden limb-only ITM, standard-dose bleomycin ECT results in durable local response. Treatment naivety, low tumour volume, hexagonal electrode application, retreatment, and post-ECT ulceration predict response. CR and concurrent treatment correlate with improved regional control and survival outcomes. Combination with checkpoint inhibitors is safe but lacks conclusive support.

Case report: Complete clinical remission of feline progressive histiocytosis after multimodal treatment including electrochemotherapy

Feline histiocytic diseases are uncommon and rarely reported. Feline progressive histiocytosis (FPH) is the most common histiocytic disease in cats, predominantly affecting middle-aged animals. The most common presentation is the cutaneous form with solitary or multiple cutaneous nodules. A female, mixed-breed 6-year-old cat was presented with a 9-month history of a nodule in the nasal planum and was diagnosed by histopathology with histiocytic proliferation. At the time of diagnosis, new nodules were discovered on the lower lip, digit, and two lesions in the tail region, with the largest measuring 1.5 cm. Supplementary immunohistochemistry, showed immunolabeling for Iba-1 that in combination with the clinical course of the disease, confirmed the diagnosis of FPH. No response to chemotherapy treatment with lomustine alternated with doxorubicin was achieved. Toceranib phosphate resulted in a transient response and, stable disease for a short period (6 weeks). Electrochemotherapy with bleomycin was initiated and resulted in partial remission. Later on, chlorambucil was also started. Ultimately, the combination of all three treatments led to a complete response and disappearance of all the lesions. FPH is considered a disease resistant to various treatments, and effective treatments have not been reported. In this case report, we describe a successful multimodal therapeutic approach that resulted in complete resolution of the FPH and long-term survival (460 days without external lesions at the time of death). Further studies are necessary to confirm the efficacy of this therapeutic approach.

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

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

The Efficacy of Electrochemotherapy with Dacarbazine on Melanoma Cells

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

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Investigation of integrated time nanosecond pulse irreversible electroporation against spontaneous equine melanoma

Introduction

Integrated time nanosecond pulse irreversible electroporation (INSPIRE) is a novel tumor ablation modality that employs high voltage, alternating polarity waveforms to induce cell death in a well-defined volume while sparing the underlying tissue. This study aimed to demonstrate the in vivo efficacy of INSPIRE against spontaneous melanoma in standing, awake horses.

Methods

A custom applicator and a pulse generation system were utilized in a pilot study to treat horses presenting with spontaneous melanoma. INSPIRE treatments were administered to 32 tumors across 6 horses and an additional 13 tumors were followed to act as untreated controls. Tumors were tracked over a 43-85 day period following a single INSPIRE treatment. Pulse widths of 500ns and 2000ns with voltages between 1000 V and 2000 V were investigated to determine the effect of these variables on treatment outcomes.

Results

Treatments administered at the lowest voltage (1000 V) reduced tumor volumes by 11 to 15%. Higher voltage (2000 V) treatments reduced tumor volumes by 84 to 88% and eliminated 33% and 80% of tumors when 500 ns and 2000 ns pulses were administered, respectively.

Discussion

Promising results were achieved without the use of chemotherapeutics, the use of general anesthesia, or the need for surgical resection in regions which are challenging to keep sterile. This novel therapeutic approach has the potential to expand the role of pulsed electric fields in veterinary patients, especially when general anesthesia is contraindicated, and warrants future studies to demonstrate the efficacy of INSPIRE as a solid tumor treatment.

Calcium Electroporation versus Electrochemotherapy with Bleomycin in an In Vivo CAM-Based Uveal Melanoma Xenograft Model

Despite recent advancements in the diagnosis and treatment of uveal melanoma (UM), its metastatic rate remains high and is accompanied by a highly dismal prognosis, constituting an unmet need for the development of novel adjuvant therapeutic strategies. We established an in vivo chick chorioallantoic membrane (CAM)-based UM xenograft model from UPMD2 and UPMM3 cell lines to examine its feasibility for the improvement of selection of drug candidates. The efficacy of calcium electroporation (CaEP) with 5 or 10 mM calcium chloride (Ca) and electrochemotherapy (ECT) with 1 or 2.5 µg/mL bleomycin in comparison to monotherapy with the tested drug or electroporation (EP) alone was investigated on the generated UM tumors. CaEP and ECT showed a similar reduction of proliferation and melanocytic expansion with a dose-dependent effect for bleomycin, whereas CaEP induced a significant increase of the apoptosis and a reduction of vascularization with varying sensitivity for the two xenograft types. Our in vivo results suggest that CaEP and ECT may facilitate the adequate local tumor control and contribute to the preservation of the bulbus, potentially opening new horizons in the adjuvant treatment of advanced UM.

European e-Delphi process to define expert consensus on electrochemotherapy treatment indications, procedural aspects, and quality indicators in melanoma

BACKGROUND

Skin metastases are an important co-morbidity in melanoma. Despite broad adoption, electrochemotherapy implementation is hindered by a lack of treatment indications, uncertainty regarding procedural aspects, and the absence of quality indicators. An expert consensus may harmonize the approach among centres and facilitate comparison with other therapies.

METHODS

An interdisciplinary panel was recruited for a three-round e-Delphi survey. A literature-based 113-item questionnaire was proposed to 160 professionals from 53 European centres. Participants rated each item for relevance and degree of agreement on a five-point Likert scale, and received anonymous controlled feedback to allow revision. The items that reached concordant agreement in two successive iterations were included in the final consensus list. In the third round, quality indicator benchmarks were defined using a real-time Delphi method.

RESULTS

The initial working group included 122 respondents, of whom 100 (82 per cent) completed the first round, thus qualifying for inclusion in the expert panel (49 surgeons, 29 dermatologists, 15 medical oncologists, three radiotherapists, two nurse specialists, two clinician scientists). The completion rate was 97 per cent (97 of 100) and 93 per cent (90 of 97) in the second and third rounds respectively. The final consensus list included 54 statements with benchmarks (treatment indications, (37); procedural aspects, (1); quality indicators, (16)).

CONCLUSION

An expert panel achieved consensus on the use of electrochemotherapy in melanoma, with a core set of statements providing general direction to electrochemotherapy users to refine indications, align clinical practices, and promote quality assurance programmes and local audits. The residual controversial topics set future research priorities to improve patient care.

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

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

Effects of Electrochemotherapy on Immunologically Important Modifications in Tumor Cells

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

Induction of Bystander and Abscopal Effects after Electroporation-Based Treatments

Electroporation-based antitumor therapies, including bleomycin electrotransfer, calcium electroporation, and irreversible electroporation, are very effective on directly treated tumors, but have no or low effect on distal nodules. In this study, we aimed to investigate the abscopal effect following calcium electroporation and bleomycin electrotransfer and to find out the effect of the increase of IL-2 serum concentration by muscle transfection. The bystander effect was analyzed in in vitro studies on 4T1tumor cells, while abscopal effect was investigated in an in vivo setting using Balb/c mice bearing 4T1 tumors. ELISA was used to monitor IL-2 serum concentration. We showed that, similarly to cell treatment with bleomycin electrotransfer, the bystander effect occurs also following calcium electroporation and that these effects can be combined. Combination of these treatments also resulted in the enhancement of the abscopal effect in vivo. Since these treatments resulted in an increase of IL-2 serum concentration only in mice bearing one but not two tumors, we increased IL-2 serum concentration by muscle transfection. Although this did not enhance the abscopal effect of combined tumor treatment using calcium electroporation and bleomycin electrotransfer, boosting of IL-2 serum concentration had a significant inhibitory effect on directly treated tumors.