Electrochemotherapy--a novel method of cancer treatment

Cardiac blood vessels and irreversible electroporation: findings from pulsed field ablation

The clinical use of irreversible electroporation in invasive cardiac laboratories, termed pulsed field ablation (PFA), is gaining early enthusiasm among electrophysiologists for the management of both atrial and ventricular arrhythmogenic substrates. Though electroporation is regularly employed in other branches of science and medicine, concerns regarding the acute and permanent vascular effects of PFA remain. This comprehensive review aims to summarize the preclinical and adult clinical data published to date on PFA's effects on pulmonary veins and coronary arteries. These data will be contrasted with the incidences of iatrogenic pulmonary vein stenosis and coronary artery injury secondary to thermal cardiac ablation modalities, namely radiofrequency energy, laser energy, and liquid nitrogen-based cryoablation.

Opportunities and Challenges in Catheter-Based Irreversible Electroporation for Ventricular Tachycardia

The use of catheter-based irreversible electroporation in clinical cardiac laboratories, termed pulsed-field ablation (PFA), is gaining international momentum among cardiac electrophysiology proceduralists for the non-thermal management of both atrial and ventricular tachyrhythmogenic substrates. One area of potential application for PFA is in the mitigation of ventricular tachycardia (VT) risk in the setting of ischemia-mediated myocardial fibrosis, as evidenced by recently published clinical case reports. The efficacy of tissue electroporation has been documented in other branches of science and medicine; however, ventricular PFA's potential advantages and pitfalls are less understood. This comprehensive review will briefly summarize the pathophysiological mechanisms underlying VT and then summarize the pre-clinical and adult clinical data published to date on PFA's effectiveness in treating monomorphic VT. These data will be contrasted with the effectiveness ascribed to thermal cardiac ablation modalities to treat VT, namely radiofrequency energy and liquid nitrogen-based cryoablation.

Electrochemotherapy Plus IL-2+IL-12 Gene Electrotransfer in Spontaneous Inoperable Stage III-IV Canine Oral Malignant Melanoma

Electrochemotherapy (ECT) is a standard of care in veterinary and human oncology. The treatment induces a well-characterized local immune response which is not able to induce a systemic response. In this retrospective cohort study, we evaluated the addition of gene electrotransfer (GET) of canine IL-2 peritumorally and IL-12 intramuscularly to enhance the immune response. Thirty canine patients with inoperable oral malignant melanoma were included. Ten patients received ECT+GET as the treatment group, while twenty patients received ECT as the control group. Intravenous bleomycin for the ECT was used in both groups. All patients had compromised lymph nodes which were surgically removed. Plasma levels of interleukins, local response rate, overall survival, and progression-free survival were evaluated. The results show that IL-2 and IL-12 expression peaked around days 7-14 after transfection. Both groups showed similar local response rates and overall survival times. However, progression-free survival resulted significantly better in the ECT+GET group, which is a better indicator than overall survival, as it is not influenced by the criterion used for performing euthanasia. We can conclude that the combination of ECT+GET using IL-2 and IL-12 improves treatment outcomes by slowing down tumoral progression in stage III-IV inoperable canine oral malignant melanoma.

The distinguishing electrical properties of cancer cells

In recent decades, medical research has been primarily focused on the inherited aspect of cancers, despite the reality that only 5-10% of tumours discovered are derived from genetic causes. Cancer is a broad term, and therefore it is inaccurate to address it as a purely genetic disease. Understanding cancer cells' behaviour is the first step in countering them. Behind the scenes, there is a complicated network of environmental factors, DNA errors, metabolic shifts, and electrostatic alterations that build over time and lead to the illness's development. This latter aspect has been analyzed in previous studies, but how the different electrical changes integrate and affect each other is rarely examined. Every cell in the human body possesses electrical properties that are essential for proper behaviour both within and outside of the cell itself. It is not yet clear whether these changes correlate with cell mutation in cancer cells, or only with their subsequent development. Either way, these aspects merit further investigation, especially with regards to their causes and consequences. Trying to block changes at various levels of occurrence or assisting in their prevention could be the key to stopping cells from becoming cancerous. Therefore, a comprehensive understanding of the current knowledge regarding the electrical landscape of cells is much needed. We review four essential electrical characteristics of cells, providing a deep understanding of the electrostatic changes in cancer cells compared to their normal counterparts. In particular, we provide an overview of intracellular and extracellular pH modifications, differences in ionic concentrations in the cytoplasm, transmembrane potential variations, and changes within mitochondria. New therapies targeting or exploiting the electrical properties of cells are developed and tested every year, such as pH-dependent carriers and tumour-treating fields. A brief section regarding the state-of-the-art of these therapies can be found at the end of this review. Finally, we highlight how these alterations integrate and potentially yield indications of cells' malignancy or metastatic index.

Tumor treating fields: An emerging treatment modality for thoracic and abdominal cavity cancers

Tumor treating fields (TTFields)-an intermediate-frequency, electric field therapy-has emerged as a promising alternative therapy for the treatment of solid cancers. Since the first publication describing the anticancer effects of TTFields in 2004 there have been numerous follow-up studies by other groups, either to confirm the efficacy of TTFields or to study the primary mechanism of interaction. The overwhelming conclusion from these in vitro studies is that TTFields reduce the viability of aggressively replicating cell lines. However, there is still speculation as to the primary mechanism for this effect; moreover, observations both in vitro and in vivo of inhibited migration and metastases have been made, which may be unrelated to the originally proposed hypothesis of replication stress. Adding to this, the in vivo environment is much more complex spatially, structurally, and involves intricate networks of cell signaling, all of which could change the efficacy of TTFields in the same way pharmaceutical interventions often struggle transitioning in vivo. Despite this, TTFields have shown promise in clinical practice on multiple cancer types, which begs the question: has the primary mechanism carried over from in vitro to in vivo or are there new mechanisms at play? The goal of this review is to highlight the current proposed mechanism of action of TTFields based primarily on in vitro experiments and animal models, provide a summary of the clinical efficacy of TTFields, and finally, propose future directions of research to identify all possible mechanisms in vivo utilizing novel tumor-on-a-chip platforms.

Electrochemotherapy to Metastatic Spinal Melanoma: A Novel Treatment of Spinal Metastasis?

STUDY DESIGN

Preliminary report of new antitumor treatment.

OBJECTIVE

To evaluate the effectiveness of electrochemotherapy as a novel treatment of spinal metastasis.

SUMMARY OF BACKGROUND DATA

Electrochemotherapy is a new antitumor treatment that combines systemic bleomycin with electric pulses delivered locally at the tumor site. These electric pulses permeabilize cell membranes in the tissue, allow bleomycin delivery diffusion inside the cells, and increase bleomycin cytotoxicity. Previous clinical studies have demonstrated the effectiveness of electrochemotherapy in the treatment of several primary and metastatic solid tumors.

METHODS

Treatment planning for electrode positioning and electrical pulse parameters was prepared for 4 needle electrodes. Mini-open surgery with a left L5 laminectomy was performed to introduce the eletrodes. The patient was treated according to the established Electrochemotherapy Protocol with Bleomycin. Clinical efficacy of electrochemotherapy was evaluated according to a visual analog scale of pain, Oswestry Disability Index 2.0, the Karnofsky Performance Scale, and Response Evaluation Criteria in Solid Tumors.

RESULTS

The assessed follow-up period was 48 months after the electrochemotherapy procedure. Neither serious electrochemotherapy-related adverse events, nor bleomycin toxicity were reported. Overall improvement in pain according to Oswestry Disability Index 2.0 and Karnofsky Performance Scale outcomes was better.

CONCLUSION

Our case represents, to our knowledge, the first one to test the potential role of electrochemotherapy as treatment of spinal metastasis. Electrochemotherapy allowed a successful treatment of metastatic spinal melanoma. However, we believe that there is a strong scientific rationale to support the potential utility of electrochemotherapy as a novel treatment of spinal metastasis, regardless of the histological types.

LEVEL OF EVIDENCE

5.

Pathology of non-thermal irreversible electroporation (N-TIRE)-induced ablation of the canine brain

This study describes the neuropathologic features of normal canine brain ablated with non-thermal irreversible electroporation (N-TIRE). The parietal cerebral cortices of four dogs were treated with N-TIRE using a dose-escalation protocol with an additional dog receiving sham treatment. Animals were allowed to recover following N-TIRE ablation and the effects of treatment were monitored with clinical and magnetic resonance imaging examinations. Brains were subjected to histopathologic and ultrastructural assessment along with Bcl-2, caspase-3, and caspase-9 immunohistochemical staining following sacrifice 72 h post-treatment. Adverse clinical effects of N-TIRE were only observed in the dog treated at the upper energy tier. MRI and neuropathologic examinations indicated that N-TIRE ablation resulted in focal regions of severe cytoarchitectural and blood-brain-barrier disruption. Lesion size correlated to the intensity of the applied electrical field. N-TIRE-induced lesions were characterized by parenchymal necrosis and hemorrhage; however, large blood vessels were preserved. A transition zone containing parenchymal edema, perivascular inflammatory cuffs, and reactive gliosis was interspersed between the necrotic focus and normal neuropil. Apoptotic labeling indices were not different between the N-TIRE-treated and control brains. This study identified N-TIRE pulse parameters that can be used to safely create circumscribed foci of brain necrosis while selectively preserving major vascular structures.

Physically facilitating drug-delivery systems

Facilitated/modulated drug-delivery systems have emerged as a possible solution for delivery of drugs of interest to pre-allocated sites at predetermined doses for predefined periods of time. Over the past decade, the use of different physical methods and mechanisms to mediate drug release and delivery has grown significantly. This emerging area of research has important implications for development of new therapeutic drugs for efficient treatments. This review aims to introduce and describe different modalities of physically facilitating drug-delivery systems that are currently in use for cancer and other diseases therapy. In particular, delivery methods based on ultrasound, electrical, magnetic and photo modulations are highlighted. Current uses and areas of improvement for these different physically facilitating drug-delivery systems are discussed. Furthermore, the main advantages and drawbacks of these technologies reviewed are compared. The review ends with a speculative viewpoint of how research is expected to evolve in the upcoming years.

Electroporation therapy in soft tissue sarcoma: a potentially effective novel treatment

Purpose. Examination of the potential of electroporation therapy (EPT) in a patient with metastatic soft tissue sarcoma. Patient. A 24-year-old male who underwent extensive resection and postoperative radiotherapy for a malignant peripheral nerve sheath tumor in the right infratemporal fossa with intracranial extension and invasion of the maxillary sinus and mandible had a recurrence in the scar of his craniotomy for which he was initially treated with doxorubicin. After discontinuation of doxorubicin he developed a metastatic mass at the same site for which he was treated with electroporation therapy. Method. The subcutaneous metastasis was infiltrated with bleomycin and electroporated. Results. Gradually the tumor became increasingly necrotic and demarcated from surrounding tissue. After 10 weeks no tumor was seen anymore. The wound healed secondarily. Discussion. Intralesional bleomycin followed by EPT is potentially effective, well tolerated, and easy to perform in well accessible soft tissue sarcoma sites.

Nonthermal irreversible electroporation for intracranial surgical applications

Object

Nonthermal irreversible electroporation (NTIRE) is a novel, minimally invasive technique to treat cancer, which is unique because of its nonthermal mechanism of tumor ablation. This paper evaluates the safety of an NTIRE procedure to lesion normal canine brain tissue.

Methods

The NTIRE procedure involved placing electrodes into a targeted area of brain in 3 dogs and delivering a series of short and intense electric pulses. The voltages of the pulses applied were varied between dogs. Another dog was used as a sham control. One additional dog was treated at an extreme voltage to determine the upper safety limits of the procedure. Ultrasonography was used at the time of the procedure to determine if the lesions could be visualized intraoperatively. The volumes of ablated tissue were then estimated on postprocedure MR imaging. Histological brain sections were then analyzed to evaluate the lesions produced.

Results

The animals tolerated the procedure with no apparent complications except for the animal that was treated at the upper voltage limit. The lesion volume appeared to decrease with decreasing voltage of applied pulses. Histological examination revealed cell death within the treated volume with a submillimeter transition zone between necrotic and normal brain.

Conclusions

The authors' results reveal that NTIRE at selected voltages can be safely administered in normal canine brain and that the volume of ablated tissue correlates with the voltage of the applied pulses. This preliminary study is the first step toward using NTIRE as a brain cancer treatment.

Electroporation therapy of skin cancer in the head and neck area

BACKGROUND

Electroporation therapy is a new cancer treatment modality in which a locally applied electrical field enhances cell membrane permeability, allowing greater intracellular accumulation of a chemotherapeutic agent.

OBJECTIVE

To evaluate the efficacy of electroporation therapy in treating basal cell and squamous cell carcinomas of the skin.

MATERIALS AND METHODS

Six patients with skin cancer of the head and neck were treated using electroporation therapy with intratumorally injected bleomycin. Orbital growth, facial nerve proximity, or proximity to cartilage of the external meatus complicated four of these tumors. The intention was curative. The follow-up period was 24 months and included biopsies after 8 weeks.

RESULTS

In four of the six patients, one treatment was enough to eradicate the tumor. In one patient, the tumor persisted even after a second treatment with electroporation therapy. A septal cartilage perforation was the only major complication. The cosmetic results were very satisfactory. One additional recurrence was recorded 6 months after the follow-up period

CONCLUSION

Electroporation therapy is a promising new cancer treatment that should be further evaluated as an alternative to surgery, especially in complicated skin cancer.

Irreversible electroporation in medicine

This is a brief introduction to the emerging field of irreversible electroporation in medicine. Certain electrical fields when applied across a cell can have as a sole effect the permeabilization of the cell membrane, presumable through the formation of nanoscale defects in the cell membrane. Sometimes this process leads to cell death, primarily when the electrical fields cause permanent permeabilization of the membrane and the consequent loss of cell homeostasis, in a process known as irreversible electroporation. This is an unusual mode of cell death that is not understood yet. While the phenomenon of irreversible electroporation may have been known for centuries it has become only recently rigorously considered in medicine for various applications of tissue ablation. A brief historical perspective of irreversible electroporation is presented and recent studies in the field are discussed.

A High-Voltage Pulse Generation Instrument for Electrochemotherapy Method

Electrochemotherapy (ECT) is a new method that uses anticancer drugs delivery with intensive electrical pulses. Recently, ECT as the treatment method can be applied for basal cell and spin cell carcinoma and for melanoma metastases. In this paper, a new design of a high voltage pulse generator with variable output pulse magnitude, repetition frequency, and pulse duration is presented. Furthermore, it has presented the basic theory of ECT, the importance/advantages against other cancer treatment methods, the theoretical model of electroporated cell membrane, and the application ways of ECT method. The proposed instrument is suitable for effective drug delivery of ECT in anti-tumor treatment. Also, this instrument can be applied to gene transfer/therapy methods.

Stimulation of Capacitative Calcium Entry in HL-60 Cells by Nanosecond Pulsed Electric Fields

Nanosecond pulsed electric fields (nsPEFs) are hypothesized to affect intracellular structures in living cells providing a new means to modulate cell signal transduction mechanisms. The effects of nsPEFs on the release of internal calcium and activation of calcium influx in HL-60 cells were investigated by using real time fluorescent microscopy with Fluo-3 and fluorometry with Fura-2. nsPEFs induced an increase in intracellular calcium levels that was seen in all cells. With pulses of 60 ns duration and electric fields between 4 and 15 kV/cm, intracellular calcium increased 200-700 nM, respectively, above basal levels (approximately 100 nM), while the uptake of propidium iodide was absent. This suggests that increases in intracellular calcium were not because of plasma membrane electroporation. nsPEF and the purinergic agonist UTP induced calcium mobilization in the presence and absence of extracellular calcium with similar kinetics and appeared to target the same inositol 1,4,5-trisphosphate- and thapsigargin-sensitive calcium pools in the endoplasmic reticulum. For cells exposed to either nsPEF or UTP in the absence of extracellular calcium, there was an electric field-dependent or UTP dose-dependent increase in capacitative calcium entry when calcium was added to the extracellular media. These findings suggest that nsPEFs, like ligand-mediated responses, release calcium from similar internal calcium pools and thus activate plasma membrane calcium influx channels or capacitative calcium entry.

Electric field of a six-needle array electrode used in drug and DNA delivery in vivo: analytical versus numerical solution

We present an analytical solution for the electrical potential and field established by a six-needle array electroporation electrode, which is used in vivo for cancer treatment and DNA delivery. The analytical solution closely matches the numerical solution obtained with the finite element method: the mean error is less than 0.6%.

Nanosecond, high-intensity pulsed electric fields induce apoptosis in human cells

Electroporation by using pulsed electric fields with long durations compared with the charging time of the plasma membrane can induce cell fusion or introduce xenomolecules into cells. Nanosecond pulse power technology generates pulses with high-intensity electric fields, but with such short durations that the charging time of the plasma membrane is not reached, but intracellular membranes are affected. To determine more specifically their effects on cell structure and function, human cells were exposed to high intensity (up to 300 kV/cm) nanosecond (10-300 ns) pulsed electric fields (nsPEF) and were analyzed at the cellular and molecular levels. As the pulse duration decreased, plasma membrane electroporation decreased and appearances of apoptosis markers were delayed. NsPEF induced apoptosis within tens of minutes, depending on the pulse duration. Annexin-V binding, caspase activation, decreased forward light scatter, and cytochrome c release into the cytoplasm were coincident. Apoptosis was caspase- and mitochondria-dependent but independent of plasma membrane electroporation and thermal changes. The results suggest that with decreasing pulse durations, nsPEF modulate cell signaling from the plasma membrane to intracellular structures and functions. NsPEF technology provides a unique, high-power, energy-independent tool to recruit plasma membrane and/or intracellular signaling mechanisms that can delete aberrant cells by apoptosis.

Bleomycin-mediated electrochemotherapy in mouse NR-S1 carcinoma

PURPOSE

To determine whether or not low-voltage electrochemotherapy has cell killing effects.

MATERIALS

Dorsally transplanted NR-S1 carcinomas in mice were stimulated with electric pulses (40 V/cm) after bleomycin (1 microg/g) had been injected around them. The tumors were fixed with a forceps electrode and electroporation was carried out three times a day for 4 days per week for 2 weeks.

RESULTS

After 8 weeks of experimentation, the tumor had disappeared in four of the ten mice. The cell killing effects were mainly apoptosis and necrosis.

CONCLUSION

Electroporation should be clinically introduced into the cosmetic and functional treatment of the head and neck region. Further investigation is also necessary to determine suitable carcinostatic agents and clarify the electric pulse conditions.

Joule heating during solid tissue electroporation

The application of high-voltage pulses to biological tissue causes not only electroporation, a non-thermal phenomenon of pore creation within a lipid membrane due to an elevated electric field, but also significant heating. Once a biological membrane is porated, the current density increases several times, causing Joule heating. A combined experimental and theoretical study is reported. The theoretical temperature rise for a 1.25 kV cm(-1), 6 ms pulse is about 11.2 K for a tissue conductivity of 0.5 S m(-1) (i.e. myocardial tissue) during high-voltage application. Owing to the inhomogeneous electric field obtained with the use of needle electrodes, the temperature rises first at the electrodes, where the field strength reaches a maximum. Only for highly conductive tissue such as muscle was a temperature effect primarily observed in the bulk. Even if the temperature effect is biologically insignificant, it can affect the creation of stabile aqueous pathways by electroporation. The calculation of temperature distribution during high-voltage application, taking the electric field strength and the heat transfer into account, can be a useful tool for electrode optimisation.

Inhibition of established subcutaneous and metastatic murine tumors by intramuscular electroporation of the interleukin-12 gene

In vivo electroporation (EP) of the murine interleukin-12 (IL-12) gene in an expression plasmid (pIL-12) was evaluated for antitumor activity. EP transfer of pIL-12 into mouse quadriceps muscles elicited significant levels of serum IL-12 and interferon-gamma. Intramuscular EP of pIL-12 resulted in complete regression or substantial inhibition of 38C13 B-cell lymphoma, whereas pIL-12 delivered by gene gun or intramuscular injection without EP showed little therapeutic effect. Impressive antitumor activity by intramuscular EP was also demonstrated in animals with advanced malignant disease. At day 14 after 38C13 tumor inoculation, all animals were found to carry large tumors and to have metastases; without treatment, most died within a week. A single intramuscular EP of pIL-12 resulted in regression of 50% of large subcutaneous tumors and significantly prolonged the lifespan of these animals. Moreover, animals that were previously cured of 38C13 tumors by in vivo EP treatment significantly suppressed tumor growth when challenged 60 days later. In vivo EP of the IL-12 gene was also effective in suppressing subcutaneous and lung metastatic tumors of CT-26 colon adenocarcinoma and B16F1 melanoma cells. Together, these results show that intramuscular electrotransfer of the IL-12 gene may represent a simple and effective strategy for cancer treatment.

Induction of dental pulp stem cell differentiation into odontoblasts by electroporation-mediated gene delivery of growth/differentiation factor 11 (Gdf11)

The long-term goal of dental treatment is to preserve teeth and prolong their function. In dental caries an efficient method is to cap the exposed dental pulp and conserve the pulp tissue with reparative dentin. We examined whether growth/differentiation factor 11 (GDF11), a morphogen could enhance the healing potential of pulp tissue to induce differentiation of pulp stem cells into odontoblasts by electroporation-mediated gene delivery. Recombinant human GDF11 induced the expression of dentin sialoprotein (Dsp), a differentiation marker for odontoblasts, in mouse dental papilla mesenchyme in organ culture. The Gdf11 cDNA plasmid which was transferred into mesenchymal cells derived from mouse dental papilla by electroporation, induced the expression of Dsp. The in vivo transfer of Gdf11 by electroporation stimulated the reparative dentin formation during pulpal wound healing in canine teeth. These results provide the scientific basis and rationale for gene therapy for endodontic treatments in oral medicine and dentistry.

Intratumoral cancer chemotherapy and immunotherapy: opportunities for nonsystemic preoperative drug delivery

The recent literature documents the growing interest in local intratumoral chemotherapy as well as systemic preoperative chemotherapy with evidence for improved outcomes using these therapeutic modalities. Nevertheless, with few exceptions, the conventional wisdom and standard of care for clinical and surgical oncology remains surgery followed by radiation and/or systemic chemotherapy, as deemed appropriate based on clinical findings. This, in spite of the fact that the toxicity of conventional systemic chemotherapy and immunotherapy affords limited effectiveness and frequently compromises the quality of life for patients. Indeed, with systemic chemotherapy, the oncologist (and the patient) often walks a fine line between attempting tumour remission with prolonged survival and damaging the patient's vital functions to the point of death. In this context, it has probably been obvious for more than 100 years, due in part to the pioneering work of Ehrlich (1878), that targeted or localized drug delivery should be a major goal of chemotherapy. However, there is still only limited clinical use of nonsystemic intratumoral chemotherapy for even those high mortality cancers which are characterized by well defined primary lesions i.e. breast, colorectal, lung, prostate, and skin. There has been a proliferation of intratumoral chemotherapy and immunotherapy research during the past two to three years. It is therefore the objective of this review to focus much more attention upon intratumoral therapeutic concepts which could limit adverse systemic events and which might combine clinically feasible methods for localized preoperative chemotherapy and/or immunotherapy with surgery. Since our review of intratumoral chemoimmunotherapy almost 20 years ago (McLaughlin & Goldberg 1983), there have been few comprehensive reviews of this field; only one of broad scope (Brincker 1993), three devoted specifically to gliomas (Tomita 1991; Walter et al. 1995; Haroun & Brem 2000), one on hepatomas (Venook 2000), one concerning veterinary applications (Theon 1998), and one older review of dermatological applications (Goette 1981). However, none have shed light on practical opportunities for combining intratumoral therapy with subsequent surgical resection. Given the state-of-the-art in clinical and surgical oncology, and the advances that have been made in intratumoral drug delivery, minimally invasive tumour access i.e. fine needle biopsy, new drugs and drug delivery systems, and preoperative chemotherapy, it is timely to present a review of studies which may suggest future opportunities for safer, more effective, and clinically practical non-systemic therapy.

Electrochemotherapy in primary and metastatic skin tumors: phase II trial using intralesional bleomycin

BACKGROUND

Surgery and/or radiotherapy are the elective therapies for most primary skin cancers. Nevertheless, some patients develop recurrences, and chemotherapy has resulted in poor complete responses. Permeabilization of the cell membrane by electric pulses allows bleomycin to enter into the cell, increasing possibility of cytotoxicity.

METHODS

From November 1998 through November 1999, 15 patients with 38 skin lesions participated in a phase II prospective clinical trial, using intralesional bleomycin plus electric pulses delivered 10 min after bleomycin injection, which lasted 100 microsec each at field strength of 1,300 V/cm and a frequency of 1 Hz. There were basal cell carcinomas (BCC) (nine lesions), in-transit metastasis of melanoma (MM) (two patients/13 nodules), squamous cell carcinomas (SCC) of the upper aerodigestive tract metastatic to the skin (two patients/two nodules), and skin metastases from breast cancer (two patients/14 nodules). Mean follow-up was 8.6 months.

RESULTS

Overall objective responses were 98%, with complete responses achieved in 49%, partial responses in 49%, and no responses in 2%. No complications were documented related to the treatment and tolerance was adequate.

CONCLUSIONS

Electrochemotherapy (ECT) is a new cancer modality of treatment that is effective in a variety of skin cancers. This treatment represents an excellent alternative to standard surgery or radiotherapy, with an outpatient-based treatment applied in one to three sessions. The major impact was obtained in BBC, but ECT is a useful palliative therapy in melanoma, breast cancer, or SCC. More experience and longer follow-up are required to determine long-term results.

Electroporation therapy for head and neck cancer including carotid artery involvement

OBJECTIVES

Electroporation therapy with intralesional bleomycin (EPT) is a novel, technically simple outpatient technique in which high-voltage electric impulses delivered into a neoplasm transiently increase cell membrane permeability to large molecules, including cytotoxic agents, causing localized progressive necrosis. Unlike many laser ablation methods, EPT can treat bulky tumors (>2 cm) with complete penetration. Our recent publication confirms an excellent response rate in the use of EPT in a clinical trial.

STUDY DESIGN, PATIENTS, AND METHODS

Following our initial prospective study report in 1998, we have followed our entire initial cohort (10 patients) of patients with head and neck cancer beyond 24-months follow-up. Additionally, we have used this approach to treat four additional patients (total: 9 males/5 females) with upper aerodigestive tract squamous cell carcinoma, including three with internal carotid artery (ICA) involvement up to or within the skull base. Two patients underwent preoperative balloon test occlusion with cerebral perfusion studies followed by carotid embolization. EPT was then done safely at least 2 weeks later to avoid the temporary hypercoagulable state.

RESULTS

Within the overall cohort (14 patients) 6 patients had a complete response, 6 had a partial response, and 2 did not respond (overall 85.7% response rate). Both patients with ICA involvement had a partial or complete response to treatment; neither patient had a hemorrhagic or neurologic complication. Overall, 13 of the 14 patients were treated for persistent or recurrent head and neck cancer. Two of the four patients with early recurrent stage tumors had no evidence of recurrence after EPT with an average follow-up of 31.5 months. The overall early stage tumor group had four complete responders out of five (80%). On the contrary, only 2 of 9 patients with advanced recurrent stage tumors were disease-free at 18 months. Morbidity was low for early stage tumors, but higher for advanced tumors with complications, including poor wound healing, dysphagia, and osteomyelitis. There were no treatment-related deaths.

CONCLUSION

We found EPT to be safe and efficacious in patients with head and neck cancer, even with internal carotid artery involvement. Patients with early stage recurrences have the potential for prolonged survival beyond 2 years without the morbidity of surgery and radiation or toxicity of systemic chemotherapy. Because of its superb access qualities even for bulky tumors, EPT is a potential method of delivery for other tumoricidal agents such as in genetic-altering schemes.

Evidence for roles of the activating function in electric stimulation

The hypothesis that the activating function drives transmembrane voltage changes (delta Vm) has been tested in hearts. Optical delta Vm were measured during activating functions produced with nonuniform and uniform transparent electrodes. When a nonuniform electrode was used to produce [equation: see text], the signs of delta Vm and [equation: see text] matched. The extracellular voltage gradients, often assumed important, did not predict delta Vm. When a uniform electrode was used to eliminate [equation: see text], the signs of delta Vm matched the signs of [equation: see text] estimated from variations in heart width. Demonstration of the activating function as a determinant of stimulation may improve research and therapy that use electric stimulation.

Endoscopic and electroporation therapy of paranasal sinus tumors

The purpose of this article is to introduce the concept of endoscopic and electroporation therapy for the treatment of sinonasal carcinomas. Electroporation therapy is a technique that combines intralesional injection of bleomycin combined with application of high-voltage square wave electrical impulse into the tumor. A transient increase in cell membrane permeability allows intracellular entry of bleomycin, with subsequent cytotoxicity. Two cases of sinonasal cancer were treated with this technique. One patient had complete response and is free of disease at 20 months. The other had partial response with control of the disease up to a year. Endoscopic electroporation therapy is potentially a minimally invasive method for the treatment of sinonasal malignancies in an experimental setting where other treatment options do not exist. Phase II/III national clinical trials have been initiated to study the efficacy of electroporation therapy.

Highly efficient electro-gene therapy of solid tumor by using an expression plasmid for the herpes simplex virus thymidine kinase gene

We report successful electro-gene therapy (EGT) by using plasmid DNA for tumor-bearing mice. Subcutaneously inoculated CT26 tumor was subjected to EGT, which consists of intratumoral injection of a naked plasmid encoding a marker gene or a therapeutic gene, followed by in vivo electroporation (EP). When this treatment modality is carried out with the plasmid DNA for the green fluorescent protein gene, followed by in vivo EP with the optimized pulse parameters, numerous intensely bright green fluorescent signals appeared within the tumor. EGT, by using the "A" fragment of the diphtheria toxin gene significantly inhibited the growth of tumors, by about 30%, on the flank of mice. With the herpes simplex virus thymidine kinase gene, followed by systemic injection of ganciclovir, EGT was far more effective in retarding tumor growth, varying between 50% and 90%, compared with the other controls. Based on these results, it appears that EGT can be used successfully for treating murine solid tumors.

In vivo antitumor effects of electrochemotherapy in a tongue cancer model

PURPOSE

This study investigated the in vivo antitumor effects of electrochemotherapy (ECT) using electroporation and bleomycin in a hamster tongue cancer model to assess its clinical applicability.

MATERIALS AND METHODS

Twenty animals with chemically induced tongue cancer were divided into four experimental groups designated B-E-, B-E+, B+E-, and B+E+. The B+E+ and B+E- groups received an intraperitoneal injection of 100 microg bleomycin. Fifteen minutes after the injection, the B+E+ animals received electric pulses. The B-E+ group received only electric pulses. The B-E- group received neither bleomycin nor electric pulses. Each group received the same treatment twice. The antitumor effects were assessed based on tumor volume reduction and histologic findings.

RESULTS

The B+E+ group showed remarkable tumor volume reduction, decreasing an average to 8.8% of its original volume 14 days after the treatment. Complete loss of the protruding tumor was observed in two of the five animals. Histologically, the tumors of the B+E+ group consisted of severely degenerated tumor cells and desquamative keratinizing cells. No living cancer cells were detected in three animals. The B+E-, B-E+, and B-E- groups showed progressive tumor growth, exceeding 200% of initial tumor volume during the experimental period.

CONCLUSION

The current study showed remarkable antitumor effects of ECT with bleomycin in the hamster tongue cancer model. ECT with bleomycin may be clinically applicable to the treatment of oral cancer.

The comparative benefits of glaucoma filtering surgery with an electric-pulse targeted drug delivery system demonstrated in an animal model

PURPOSE

To evaluate the safety and effectiveness of glaucoma filtering surgery performed with the adjunctive use of bleomycin administered in conjunction with electric pulses (EP).

DESIGN

Experimental study in rabbits. CONTROLS AND METHODS: Trabeculectomies were performed on pigmented rabbits (2 to 2.5 kg) using the following adjunctive treatments: 5 microM of topical bleomycin and EP (5V, 50 msec, 8 pulses) (group A: B+E+, n=15); bleomycin but no EP (group B: B+E-, n=15); 5 ,uM mitomycin C (MMC) and EP (group C: M+E+, n= 10); MMC but no EP (group D: M+E-, n=10); EP alone (group E: E+, n=10); and no adjunctive treatment (group F: E-, negative control, n=10).

MAIN OUTCOME MEASURES

Intraocular pressure (IOP) was measured regularly for 60 days after the operation. Bleb formation and the condition of the conjunctiva, cornea, and retina were also regularly evaluated. Histologic studies were performed by light microscopy, and retinal functions were evaluated by electroretinography.

RESULTS

Postoperative IOP was significantly lower than the preoperative level in all the animals until day 7. However, in groups E and F (the negative control) it returned to the preoperative level after day 7, and in groups B, C, and D after 15 days. The IOP of group A remained lower even on day 40. The average amount IOP was lowered or increased on day 20 was -6.4 mmHg (P < 0.05) in group A; -0.2 mmHg in group B; +1.2 mmHg in group C; and -3.25 mmHg in group D. The survival rate of the filtering blebs on day 20 was significantly higher in group A than in the other groups. Clinical and histologic studies uncovered no pathologic findings in any intra- or paraocular tissues. Electroretinographic evaluation of retinal function in group A showed no apparent change over the 60 days of the study.

CONCLUSION

Glaucoma filtering surgery in rabbits with the adjunctive use of bleomycin in conjunction with EP significantly lowered IOP for up to 40 days without clinically, morphologically, or functionally harming intraocular tissues.

Electroporation therapy: a new approach for the treatment of head and neck cancer

Electroporation can deliver exogenous molecules like drugs and genes into cells by pulsed electric fields through a temporary increase in cell membrane permeability. This effect is being used for the treatment of cancer by intratumoral injection of low dosage of an otherwise marginally effective chemotherapeutic drug, bleomycin. Application of a pulsed electric field results in substantially higher uptake of the drug and enhanced killing of the cancer cells than is possible by conventional methods. The MedPulser, a new treatment system for local electroporation therapy (EPT) of head and neck tumors was developed and is described in this paper. EPT with bleomycin has been found to be very effective in killing cancer cells in vitro, in mouse tumor xenografts in vivo, and in tumors in humans. Ten head and neck cancer patients with recurring or unresponsive tumors were enrolled in a Phase I/II clinical trial. Treatment of the entire tumor mass in each of eight patients resulted in five complete responses confirmed by biopsy and MRI, and three partial responses (> or = 50% shrinkage). Two additional patients who received partial treatment of their tumor mass had local response where treated, but no overall lesion remission. Duration of the complete responses ranges from 2-10 months to date. All patients tolerated the treatment well with no significant local or systemic adverse effects.

Iontophoresis and electroporation: comparisons and contrasts

The techniques of iontophoresis and electroporation can be used to enhance topical and transdermal drug delivery. Iontophoresis applies a small low voltage (typically 10 V or less) continuous constant current (typically 0.5 mA/cm2 or less) to push a charged drug into skin or other tissue. In contrast, electroporation applies a high voltage (typically, ?100 V) pulse for a very short (micros-ms) duration to permeabilize the skin. This electric assistance of drug delivery across skin will expand the scope of transdermal delivery to hydrophilic macromolecules such as the drugs of biotechnology. These two techniques differ in several aspects such as the mode of application and pathways of transport but can be used together for effective drug delivery. Iontophoresis is already used clinically in physical therapy clinics and is close to commercialization for development of a systemic delivery patch with miniaturized circuits and similar in overall size to a passive patch. The use of electroporation for drug delivery is relatively new and is being actively researched.

Electrical stimulation prolongs the survival days of leukemic mice treated with methotrexate

To investigate effects of electrical stimulation on survival days of leukemic mice treated with methotrexate (MTX), L1210-bearing mice were treated by MTX and calcium folinate (leucovorin) rescue therapy (MTX: 400 mg/kg, followed by leucovorin at the dose of 7.5 mg/kg at 8, 15 and 24 hr after MTX) under electrical stimulation (foot shock: shock amplitude, 0.4 mA; voltage, 60-100 V/cm; shock duration, 5 sec; frequency, 0.5 Hz) of various lengths. The survival days were significantly prolonged by 6-hr electrical stimulation in combination with MTX, while plasma MTX concentrations and pharmacokinetic parameters such as the area under the curve (AUC-12 hr) and clearance (CL) were not significantly altered. Psychological stress did not alter the efficacy of MTX in the communication box paradigm. Amplified efficacy of MTX was shown in a length-dependent manner when electrical stimulation of various lengths were applied to L1210-bearing mice.

Electrical field and current distributions in electrochemotherapy

Electrochemotherapy is a method for cancer treatment consisting in combining intratumor injection of cytotoxic agent with the application of intensive electrical stimuli. Thus transient cell membranes permeabilization is created, allowing the agent to better exercise its destroying effect. Positive results have been published in the treatment of cutaneous malignant formations and other types of cancer are under consideration. The electrode configurations presently used are based mainly on empirical treatment results. In vivo imaging of stimulation currents was attempted in animal models. A preliminary study revealed that having in view the relatively high voltages and currents, there was a virtually resistive load to the electrical source. Assuming a homogeneous medium, potential and current distributions were modeled and studied. The results could help in selection of specific electrode designs, depending on tumor size and location. An optimization of the voltages and/or currents by different electrode arrays can lead to obtaining desired field distribution.

Assessing the potential of skin electroporation for the delivery of protein- and gene-based drugs

Although transdermal drug delivery has many potential advantages, the permeability of skin to macromolecules is extremely low. However, the application of short, high-voltage pulses to electroporate skin has recently been shown to make it reversibly permeable. A number of studies have demonstrated that electroporation-mediated transdermal delivery of peptides, polysaccharides, oligonucleotides and genes may be possible at clinically relevant rates, leading to the current commercial development of electroporation techniques.

Electroporation therapy of head and neck cancer

The purpose of this paper is to introduce the concept of electroporation therapy and present our results from using this new technique combined with intralesional bleomycin in head and neck cancer patients. Electroporation therapy is a technique wherein high-voltage electric impulses delivered into a neoplasm transiently increase cell membrane permeability to large molecules, including cytotoxic agents. In this phase I/II study, extremely low-dose bleomycin sulfate was electroporated into head and neck malignant neoplasms in 10 patients. Tumor responses included 2 nonresponders, 3 partial responders, and 5 complete responders, with a mean follow-up of 40 weeks. We conclude that this technique offers promising possibilities in the local treatment of head and neck cancer.

Treatment of cutaneous and subcutaneous tumors with electrochemotherapy using intralesional bleomycin

BACKGROUND

Electrochemotherapy (ECT) is performed by locally administering a chemotherapeutic agent in combination with electric pulses. Previous clinical studies have demonstrated the effectiveness of ECT. In these initial trials, the drug was administered intravenously, followed by administration of electric pulses directly to the tumor. This study was initiated to determine whether an intralesional injection of the drug in combination with electric pulses could provide an improved result. A group of 34 patients was studied.

METHODS

The dose of intralesional bleomycin was based on tumor volume. This was followed 10 minutes later by 6 or 8 99-microsec pulses of electricity at an amplitude of 1.3 kV/cm. Both the bleomycin and the electric pulses were administered after 1% lidocaine with epinephrine solution was injected around the treatment site.

RESULTS

All patients responded to the treatment. Responses were observed in 142 (99%) of 143 metastatic nodules or primary tumors within 12 weeks, with complete responses observed in 130 (91%) of the nodules. No complete responses were observed in nodules treated with bleomycin only or electric pulses only. Random biopsies confirmed the clinical findings. All patients tolerated the procedure well, and no significant side effects were noted. Muscle contraction was evident during administration of each electric pulse but promptly subsided after the pulse.

CONCLUSIONS

ECT was shown to be an effective local treatment for cutaneous malignancies. The results suggest that ECT may have a tissue-sparing effect and result in minimal scarring. ECT may be a suitable alternative therapy for the treatment of basal cell carcinoma, local or regional recurrent melanoma, and other skin cancers.

Intrinsic sensitivity of tumor cells to bleomycin as an indicator of tumor response to electrochemotherapy

Electrochemotherapy (ECT) involves the use of locally applied electric pulses to increase delivery of chemotherapeutic drugs into cells in tissues. ECT with bleomycin (BLM) is a very effective local treatment, but different tumors have different response rates to ECT. The aim of our study was to compare the responsiveness of SA-1 and EAT tumors to BLM and ECT in vitro and in vivo, in order to find possible reasons for the observed difference in response rate. The difference in sensitivity to ECT in vitro between the SA-1 and EAT cells was 10-fold and was the same as the difference in sensitivity to chronic BLM exposure, as measured by tetrazolium-based colorimetric (MTT) assay. This difference in sensitivity between SA-1 and EAT to ECT was also reflected in tumor cure rate. A six-times lower dose of BLM was needed to obtain local tumor control in SA-1 than in EAT tumors. Therefore, we suggest that the difference in sensitivity to BLM and ECT predominantly reflects the difference in intrinsic sensitivity of the cells to BLM.

Synergistic effect of electric pulses and bleomycin on cultured rabbit subconjunctival fibroblasts

BACKGROUND

The combined effect of electric pulses (EP) and antiproliferative agents on the proliferation of rabbit Tenon's capsule fibroblasts was investigated.

METHODS

Rabbit Tenon's capsule fibroblasts were cultured. Some of these cells were exposed to various intensities of EP alone (500-2500 V/cm). Other cells were then exposed for 30 min to an antiproliferative agent: bleomycin (BLM; 0.0005-50 mumol/l), mitomycin C (MMC; 0.0005-50 mumol/l), 5-fluorouracil (5-FU; 0.05-5000 mumol/l), or streptomycin (SM; 0.0005-50 mumol/l) with or without EP (2000 V/cm, 99 mus, eight pulses). Cell proliferation was assessed by cell counting on day 3 and by a 3H-thymidine uptake assay. DNA fragmentation was assessed by flow-cytometric analysis and agarose gel electrophoresis.

RESULTS

A significant reduction in the cell number was observed only at 2500 V/cm (P < 0.05). BLM, MMC and 5-FU treatment inhibited cell proliferation in a dose-dependent manner either with or without EP (ID50: BLM alone, 0.029 mumol/l; BLM and EP, 0.00022 mumol/l; MMC alone, 41.6 mumol/l; MMC and EP, 27.5 mumol/l; 5-FU alone, 1045 mumol/l; 5-FU and EP, 690.2 mumol/l; P < 0.05). EP treatment induced an inhibitory effect of BLM on cell proliferation which was 100 times more prominent than BLM alone (0.0005 mumol/l of BLM alone 103.4 +/- 4.4%, 0.0005 mumol/l of BLM and EP 26.0 +/- 4.4%; P = 0.021). BLM treatment with EP also augmented the apoptotic-like DNA fragmentation in both a flow-cytometric DNA histogram and agarose gel-electrophoresis.

CONCLUSION

EP treatment enhanced the inhibitory effect of BLM on the cell proliferation of Tenon's capsule fibroblasts of rabbits. The combination of electric pulses and antiproliferative drug treatments may therefore reduce the necessary dose of antiproliferative agents in filtering surgery.

Intralesional bleomycin-mediated electrochemotherapy in 20 patients with basal cell carcinoma

BACKGROUND

A new anticancer therapy, electrochemotherapy (ECT), has been introduced that entails exposing cancerous tissues to short pulses of electricity during chemotherapy. This enhances cell membrane permeability and has been shown to have potent antitumor effects in vitro in animal models and in several clinical trials, including nevoid basal cell carcinoma (BCC).

OBJECTIVE

We report the effects of ECT on 20 patients with primary BCC.

METHODS

Electrical pulses were delivered to 54 tumors after administration of intralesional bleomycin sulfate.

RESULTS

Complete responses were observed in 53 (98%), and in the majority of these (94%) after a single treatment. No recurrences have been recorded with a mean of 18 months of observation.

CONCLUSION

Although these are preliminary results, ECT appears to be an effective alternative to surgical excision for the treatment of primary BCC.

Effect of electric pulses and antiproliferative drugs on cultured bovine retinal pigment epithelial cells

PURPOSE

The effect of antiproliferative agents with high voltage electric pulses (EP) on the proliferation of retinal pigment epithelial (RPE) cells was investigated.

METHODS

Bovine RPE cells were cultured and exposed briefly to an antiproliferative agent: 0.005 to 500 microM of bleomycin (BLM), 0.005 to 500 microM of mitomycin C (MMC) or 0.05 to 5000 microM of 5-fluorouracil (5-FU) with or without high voltage electric pulses (EP: 2,000V/cm, 98 microseconds, 8 pulses). Streptomycin (SM) was used as a negative control. Cell proliferation with or without antiproliferative agents was assessed on day 3. DNA fragmentation was assessed by flow cytometric analysis.

RESULTS

Treatment with BLM, MMC or 5-FU inhibited cell proliferation in a dose-dependent manner, with and without EP (p < 0.05). EP enhanced the inhibitory effect of BLM as much as 3,000 times (ID50: BLM without EP; 163.7 microM, BLM with EP; 0.0574 microM, MMC without EP; 132.4 microM, MMC with EP; 26.2 microM, 5-FU without EP; 616.4 microM, 5-FU with EP; 873.8 microM). EP treatment showed an inhibitory effect of BLM on cell proliferation more prominently than BLM alone. The cell numbers of 0.5 microM BLM treatment without EP were 87.4 +/- 11.7% (mean +/- SD), whereas the cell numbers of 0.5 microM BLM with EP were 21.1 +/- 2.16% (p < 0.005). BLM treatment with EP increased the apoptosis like DNA fragmentation in the flow cytometric DNA histogram, showing dominant accumulation in the A0 region, which is the population of DNA fragmentation. (The cell population of the A0 region: control, 3.4%; EP alone, 18.9%; BLM treatment without EP, 32.0%; with EP, 93.8%.)

CONCLUSIONS

EP treatment enhances the inhibitory effect of BLM on RPE cell proliferation. The combination of electric pulse and BLM treatment can localize the drug effect and reduce the necessary dose of the antiproliferative agent in comparison to BLM treatment alone.