Safety and feasibility of the NanoKnife system for irreversible electroporation ablative treatment of canine spontaneous intracranial gliomas

Continuous iontronic chemotherapy reduces brain tumor growth in embryonic avian in vivo models

Local and long-lasting administration of potent chemotherapeutics is a promising therapeutic intervention to increase the efficiency of chemotherapy of hard-to-treat tumors such as the most lethal brain tumors, glioblastomas (GBM). However, despite high toxicity for GBM cells, potent chemotherapeutics such as gemcitabine (Gem) cannot be widely implemented as they do not efficiently cross the blood brain barrier (BBB). As an alternative method for continuous administration of Gem, we here operate freestanding iontronic pumps - "GemIPs" - equipped with a custom-synthesized ion exchange membrane (IEM) to treat a GBM tumor in an avian embryonic in vivo system. We compare GemIP treatment effects with a topical metronomic treatment and observe that a remarkable growth inhibition was only achieved with steady dosing via GemIPs. Daily topical drug administration (at the maximum dosage that was not lethal for the embryonic host organism) did not decrease tumor sizes, while both treatment regimes caused S-phase cell cycle arrest and apoptosis. We hypothesize that the pharmacodynamic effects generate different intratumoral drug concentration profiles for each technique, which causes this difference in outcome. We created a digital model of the experiment, which proposes a fast decay in the local drug concentration for the topical daily treatment, but a long-lasting high local concentration of Gem close to the tumor area with GemIPs. Continuous chemotherapy with iontronic devices opens new possibilities in cancer treatment: the long-lasting and highly local dosing of clinically available, potent chemotherapeutics to greatly enhance treatment efficiency without systemic side-effects. SIGNIFICANCE STATEMENT: Iontronic pumps (GemIPs) provide continuous and localized administration of the chemotherapeutic gemcitabine (Gem) for treating glioblastoma in vivo. By generating high and constant drug concentrations near the vascularized growing tumor, GemIPs offer an efficient and less harmful alternative to systemic administration. Continuous GemIP dosing resulted in remarkable growth inhibition, superior to daily topical Gem application at higher doses. Our digital modelling shows the advantages of iontronic chemotherapy in overcoming limitations of burst release and transient concentration profiles, and providing precise control over dosing profiles and local distribution. This technology holds promise for future implants, could revolutionize treatment strategies, and offers a new platform for studying the influence of timing and dosing dependencies of already-established drugs in the fight against hard-to-treat tumors.

Electroporation in Translational Medicine: From Veterinary Experience to Human Oncology

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

Glioblastoma Therapy: Past, Present and Future

Glioblastoma (GB) stands out as the most prevalent and lethal form of brain cancer. Although great efforts have been made by clinicians and researchers, no significant improvement in survival has been achieved since the Stupp protocol became the standard of care (SOC) in 2005. Despite multimodality treatments, recurrence is almost universal with survival rates under 2 years after diagnosis. Here, we discuss the recent progress in our understanding of GB pathophysiology, in particular, the importance of glioma stem cells (GSCs), the tumor microenvironment conditions, and epigenetic mechanisms involved in GB growth, aggressiveness and recurrence. The discussion on therapeutic strategies first covers the SOC treatment and targeted therapies that have been shown to interfere with different signaling pathways (pRB/CDK4/RB1/P16ink4, TP53/MDM2/P14arf, PI3k/Akt-PTEN, RAS/RAF/MEK, PARP) involved in GB tumorigenesis, pathophysiology, and treatment resistance acquisition. Below, we analyze several immunotherapeutic approaches (i.e., checkpoint inhibitors, vaccines, CAR-modified NK or T cells, oncolytic virotherapy) that have been used in an attempt to enhance the immune response against GB, and thereby avoid recidivism or increase survival of GB patients. Finally, we present treatment attempts made using nanotherapies (nanometric structures having active anti-GB agents such as antibodies, chemotherapeutic/anti-angiogenic drugs or sensitizers, radionuclides, and molecules that target GB cellular receptors or open the blood-brain barrier) and non-ionizing energies (laser interstitial thermal therapy, high/low intensity focused ultrasounds, photodynamic/sonodynamic therapies and electroporation). The aim of this review is to discuss the advances and limitations of the current therapies and to present novel approaches that are under development or following clinical trials.

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.

Recovery of neurosurgical high-frequency electroporation injury in the canine brain can be accelerated by 7,8-dihydroxyflavone

BACKGROUND

Although traumatic brain injury (TBI) occurs in a very short time, the biological consequence of a TBI, such as Alzheimer's disease, may last a lifetime. To date, effective interventions are not available to improve recovery from a TBI. Herein we aimed to ascertain whether recovery of neurosurgical high-frequency irreversible electroporation (HFIRE) injury in brain tissues can be accelerated by 7,8-dihydroxyflavone (7,8-DHF).

METHODS

The HFIRE injury was induced in the right parietal cortex of 8 adult healthy and neurologically intact male dogs. Two weeks before HFIRE injury, each dog was administered orally with or without 7,8-DHF (30 mg/kg) once daily for consecutive 2 weeks (n = 4 for each group). The values of blood-brain barrier (BBB) disruption, brain edema, and cerebral infarction volumes were measured. The concentrations of beta-amyloid, interleukin-1β, interleukin-6 and tumor necrosis factor-α in the cerebrospinal fluid were measured biochemically.

RESULTS

The BBB disruption, brain edema, infarction volumes, and maximal cross-section area caused by HFIRE injury in canine brain were significantly attenuated by 7,8-DHF therapy (P < 0.0001). Additionally, 7,8-DHF significantly reduced the HFIRE-induced cerebral overproduction of beta-amyloid and proinflammatory cytokines in the cerebrospinal fluid (P < 0.0001) in dogs with HFIRE.

CONCLUSIONS

Recovery of neurosurgical HFIRE injury in canine brain tissues can be accelerated by 7,8-DHT via ameliorating BBB disruption as well as cerebral overproduction of both beta-amyloid and proinflammatory cytokines.

Childhood Brain Tumors: A Review of Strategies to Translate CNS Drug Delivery to Clinical Trials

Brain and spinal tumors affect 1 in 1000 people by 25 years of age, and have diverse histological, biological, anatomical and dissemination characteristics. A mortality of 30-40% means the majority are cured, although two-thirds have life-long disability, linked to accumulated brain injury that is acquired prior to diagnosis, and after surgery or chemo-radiotherapy. Only four drugs have been licensed globally for brain tumors in 40 years and only one for children. Most new cancer drugs in clinical trials do not cross the blood-brain barrier (BBB). Techniques to enhance brain tumor drug delivery are explored in this review, and cover those that augment penetration of the BBB, and those that bypass the BBB. Developing appropriate delivery techniques could improve patient outcomes by ensuring efficacious drug exposure to tumors (including those that are drug-resistant), reducing systemic toxicities and targeting leptomeningeal metastases. Together, this drug delivery strategy seeks to enhance the efficacy of new drugs and enable re-evaluation of existing drugs that might have previously failed because of inadequate delivery. A literature review of repurposed drugs is reported, and a range of preclinical brain tumor models available for translational development are explored.

Advancements in drug delivery methods for the treatment of brain disease

The blood-brain barrier (BBB) presents a formidable obstacle to the effective delivery of systemically administered pharmacological agents to the brain, with ~5% of candidate drugs capable of effectively penetrating the BBB. A variety of biomaterials and therapeutic delivery devices have recently been developed that facilitate drug delivery to the brain. These technologies have addressed many of the limitations imposed by the BBB by: (1) designing or modifying the physiochemical properties of therapeutic compounds to allow for transport across the BBB; (2) bypassing the BBB by administration of drugs via alternative routes; and (3) transiently disrupting the BBB (BBBD) using biophysical therapies. Here we specifically review colloidal drug carrier delivery systems, intranasal, intrathecal, and direct interstitial drug delivery methods, focused ultrasound BBBD, and pulsed electrical field induced BBBD, as well as the key features of BBB structure and function that are the mechanistic targets of these approaches. Each of these drug delivery technologies are illustrated in the context of their potential clinical applications and limitations in companion animals with naturally occurring intracranial diseases.

Lethal Electric Field Thresholds for Cerebral Cells With Irreversible Electroporation and H-FIRE Protocols: An In Vitro Three-Dimensional Cell Model Study

The lethal electric field (LEF) thresholds for three typical cerebral cells, including a malignant glioblastoma (GBM) cell line and two cell lines from the healthy blood-brain barrier (BBB), treated by irreversible electroporation (IRE) or high-frequency irreversible electroporation (H-FIRE) protocols were investigated in an in vitro three-dimensional (3D) cell model. A conventional IRE protocol (90 pulses, 1 Hz, and 100-μs pulse duration) and three novel H-FIRE protocols (1-3-1, 0.5-1-0.5, and 1-1-1) were used to treat the cerebral cells in both 3D single-cell and two-cell models. The electrical conductivity of the 3D cell model under different electric field strengths were characterized with the method of electrochemical impedance spectroscopy (EIS). Based on EIS, a numerical electrothermal model of electroporation was built for the determination of the LEF threshold with different protocols and temperature monitoring. Cell viability was assessed by fluorescence staining 6 h after the treatment. The results showed no thermal lethal effect on cells when these protocols were used. The LEF threshold for GBM cells was significantly lower than that of the healthy BBB cells. These results suggest the possibility of selective ablation of human cerebral GBM by IRE and H-FIRE treatments with no injury or reversible injury to healthy cells, and the potential use of IRE or H-FIRE for transient disruption of the BBB to allow chemotherapy to reach the tumor.

Irreversible Electroporation Balloon Therapy for Palliative Treatment of Obstructive Urethral Transitional Cell Carcinoma in Dogs

Progression of transitional cell carcinoma (TCC) in dogs often leads to urinary obstruction. This observational pilot study aimed to evaluate the safety and efficacy of irreversible electroporation (IRE) balloon therapy for the palliative treatment of TCC with partial urethral obstruction. Three client-owned dogs diagnosed with TCC causing partial urethral obstruction were enrolled. After ultrasonographic and cystoscopic examination, IRE pulse protocols were delivered through a balloon catheter device inflated within the urethral lumen. After the procedure, the patients were kept overnight for monitoring and a recheck was planned 28 days later. No complication was observed during the procedure and postprocedural monitoring. After 28 days, one dog had a complete normalization of the urine stream, one dog had stable stranguria, and one dog was presented with a urethral obstruction secondary to progression of the TCC. On recheck ultrasound, one dog had a 38% diminution of the urethral mass diameter whereas the other two dogs had a mass stable in size. IRE balloon therapy seems to be a feasible and apparently safe minimally invasive novel therapy for the palliative treatment of TCC causing urethral obstruction. Further studies are needed to better characterize the safety, efficacy, and outcome of this therapy.

High-frequency irreversible electroporation brain tumor ablation: exploring the dynamics of cell death and recovery

Improved therapeutics for malignant brain tumors are urgently needed. High-frequency irreversible electroporation (H-FIRE) is a minimally invasive, nonthermal tissue ablation technique, which utilizes high-frequency, bipolar electric pulses to precisely kill tumor cells. The mechanisms of H-FIRE-induced tumor cell death and potential for cellular recovery are incompletely characterized. We hypothesized that tumor cells treated with specific H-FIRE electric field doses can survive and retain proliferative capacity. F98 glioma and LL/2 Lewis lung carcinoma cell suspensions were treated with H-FIRE to model primary and metastatic brain cancer, respectively. Cell membrane permeability, apoptosis, metabolic viability, and proliferative capacity were temporally measured using exclusion dyes, condensed chromatin staining, WST-8 fluorescence, and clonogenic assays, respectively. Both tumor cell lines exhibited dose-dependent permeabilization, with 1,500 V/cm permitting and 3,000 V/cm inhibiting membrane recovery 24 h post-treatment. Cells treated with 1,500 V/cm demonstrated significant and progressive recovery of apoptosis and metabolic activity, in contrast to cells treated with higher H-FIRE doses. Cancer cells treated with recovery-permitting doses of H-FIRE maintained while those treated with recovery-inhibiting doses lost proliferative capacity. Taken together, our data suggest that H-FIRE induces reversible and irreversible cellular damage in a dose-dependent manner, and the presence of dose-dependent recovery mechanisms permits tumor cell proliferation.

Irreversible Electroporation: An Emerging Immunomodulatory Therapy on Solid Tumors

Irreversible electroporation (IRE), a novel non-thermal ablation technique, is utilized to ablate unresectable solid tumors and demonstrates favorable safety and efficacy in the clinic. IRE applies electric pulses to alter the cell transmembrane voltage and causes nanometer-sized membrane defects or pores in the cells, which leads to loss of cell homeostasis and ultimately results in cell death. The major drawbacks of IRE are incomplete ablation and susceptibility to recurrence, which limit its clinical application. Recent studies have shown that IRE promotes the massive release of intracellular concealed tumor antigens that become an “in-situ tumor vaccine,” inducing a potential antitumor immune response to kill residual tumor cells after ablation and inhibiting local recurrence and distant metastasis. Therefore, IRE can be regarded as a potential immunomodulatory therapy, and combined with immunotherapy, it can exhibit synergistic treatment effects on malignant tumors, which provides broad application prospects for tumor treatment. This work reviewed the current status of the clinical efficacy of IRE in tumor treatment, summarized the characteristics of local and systemic immune responses induced by IRE in tumor-bearing organisms, and analyzed the specific mechanisms of the IRE-induced immune response. Moreover, we reviewed the current research progress of IRE combined with immunotherapy in the treatment of solid tumors. Based on the findings, we present deficiencies of current preclinical studies of animal models and analyze possible reasons and solutions. We also propose possible demands for clinical research. This review aimed to provide theoretical and practical guidance for the combination of IRE with immunotherapy in the treatment of malignant tumors.

Comparison of response assessment in veterinary neuro-oncology and two volumetric neuroimaging methods to assess therapeutic brain tumour responses in veterinary patients

Standardized veterinary neuroimaging response assessment methods for brain tumours are lacking. Consequently, a response assessment in veterinary neuro-oncology (RAVNO) system which uses the sum product of orthogonal lesion diameters on 1-image section with the largest tumour area, has recently been proposed. In this retrospective study, 22 pre-treatment magnetic resonance imaging (MRI) studies from 18 dogs and four cats with suspected intracranial neoplasia were compared by a single observer to 32 post-treatment MRIs using the RAVNO system and two volumetric methods based on tumour margin or area delineation with HOROS and 3D Slicer software, respectively. Intra-observer variability was low, with no statistically significant differences in agreement index between methods (mean AI ± SD, 0.91 ± 0.06 for RAVNO; 0.86 ± 0.08 for HOROS; and 0.91 ± 0.05 for 3D slicer), indicating good reproducibility. Response assessments consisting of complete or partial responses, and stable or progressive disease, agreed in 23 out of 32 (72%) MRI evaluations using the three methods. The RAVNO system failed to identify changes in mass burden detected with volumetric methods in six cases. 3D Slicer differed from the other two methods in three cases involving cysts or necrotic tissue as it allowed for more accurate exclusion of these structures. The volumetric response assessment methods were more precise in determining changes in absolute tumour burden than RAVNO but were more time-consuming to use. Based on observed agreement between methods, low intra-observer variability and decreased time constraint, RAVNO might be a suitable response assessment method for the clinical setting.

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.

Multiparametric magnetic resonance imaging features of a canine glioblastoma model

PURPOSE

To assess glioblastoma multiforme (GBM) formation with similar imaging characteristics to human GBM using multiparametric magnetic resonance imaging (MRI) in an orthotopic xenograft canine GBM model.

MATERIALS AND METHODS

The canine GBM cell line J3T1 was subcutaneously injected into 6-week-old female BALB/c nude mice to obtain tumour fragments. Tumour fragments were implanted into adult male mongrel dog brains through surgery. Multiparametric MRI was performed with conventional MRI, diffusion-weighted imaging, and dynamic susceptibility contrast-enhanced perfusion-weighted imaging at one week and two weeks after surgery in a total of 15 surgical success cases. The presence of tumour cells, the necrotic area fraction, and the microvessel density (MVD) of the tumour on the histologic specimen were assessed. Tumour volume, diffusion, and perfusion parameters were compared at each time point using Wilcoxon signed-rank tests, and the differences between tumour and normal parenchyma were compared using unpaired t-tests. Spearman correlation analysis was performed between the imaging and histologic parameters.

RESULTS

All animals showed a peripheral enhancing lesion on MRI and confirmed the presence of a tumour through histologic analysis (92.3%). The normalized perfusion values did not show significant decreases through at least 2 weeks after the surgery (P > 0.05). There was greater cerebral blood volume and flow in the GBM than in the normal-appearing white matter (1.46 ± 0.25 vs. 1.13 ± 0.16 and 1.30 ± 0.22 vs. 1.02 ± 0.14; P < 0.001 and P < 0.001, respectively). The MVD in the histologic specimens was correlated with the cerebral blood volume in the GBM tissue (r = 0.850, P = 0.004).

CONCLUSION

Our results suggest that the canine GBM model showed perfusion imaging characteristics similar to those of humans, and it might have potential as a model to assess novel technical developments for GBM treatment.

Electroporation-Based Therapy for Brain Tumors: A Review

Electroporation-based therapy (EBT), as a high-voltage-pulse technology has been prevalent with favorable clinical outcomes in the treatment of various solid tumors. This review paper aims to promote the clinical translation of EBT for brain tumors. First, we briefly introduced the mechanism of pore formation in a cell membrane activated by external electric fields using a single cell model. Then, we summarized and discussed the current in vitro and in vivo preclinical studies, in terms of (1) the safety and effectiveness of EBT for brain tumors in animal models, and (2) the blood-brain barrier (BBB) disruption induced by EBT. Two therapeutic effects could be achieved in EBT for brain tumors simultaneously, i.e., the tumor ablation induced by irreversible electroporation (IRE) and transient BBB disruption induced by reversible electroporation (RE). The BBB disruption could potentially improve the uptake of antitumor drugs thereby enhancing brain tumor treatment. The challenges that hinder the application of EBT in the treatment of human brain tumors are discussed in the review paper as well.

Clinical features, diagnosis, and survival analysis of dogs with glioma

BACKGROUND

Gliomas in dogs remain poorly understood.

OBJECTIVES

To characterize the clinicopathologic findings, diagnostic imaging features and survival of a large sample of dogs with glioma using the Comparative Brain Tumor Consortium diagnostic classification.

ANIMALS

Ninety-one dogs with histopathological diagnosis of glioma.

METHODS

Multicentric retrospective case series. Signalment, clinicopathologic findings, diagnostic imaging characteristics, treatment, and outcome were used. Tumors were reclassified according to the new canine glioma diagnostic scheme.

RESULTS

No associations were found between clinicopathologic findings or survival and tumor type or grade. However, definitive treatments provided significantly (P = .03) improved median survival time (84 days; 95% confidence interval [CI], 45-190) compared to palliative treatment (26 days; 95% CI, 11-54). On magnetic resonance imaging (MRI), oligodendrogliomas were associated with smooth margins and T1-weighted hypointensity compared to astrocytomas (odds ratio [OR], 42.5; 95% CI, 2.42-744.97; P = .04; OR, 45.5; 95% CI, 5.78-333.33; P < .001, respectively) and undefined gliomas (OR, 84; 95% CI, 3.43-999.99; P = .02; OR, 32.3; 95% CI, 2.51-500.00; P = .008, respectively) and were more commonly in contact with the ventricles than astrocytomas (OR, 7.47; 95% CI, 1.03-53.95; P = .049). Tumor spread to neighboring brain structures was associated with high-grade glioma (OR, 6.02; 95% CI, 1.06-34.48; P = .04).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with gliomas have poor outcomes, but risk factors identified in survival analysis inform prognosis and the newly identified MRI characteristics could refine diagnosis of tumor type and grade.

Phase I trial of convection-enhanced delivery of IL13RA2 and EPHA2 receptor targeted cytotoxins in dogs with spontaneous intracranial gliomas

Background

The interleukin-13 receptor alpha 2 (IL13RA2) and ephrin type A receptor 2 (EPHA2) are attractive therapeutic targets, being expressed in ~90% of canine and human gliomas, and absent in normal brain. Clinical trials using an earlier generation IL-13 based cytotoxin showed encouraging clinical effects in human glioma, but met with technical barriers associated with the convection-enhanced delivery (CED) method. In this study, IL-13 mutant and ephrin A1 (EFNA1)–based bacterial cytotoxins targeted to IL13RA2 and EPHA2 receptors, respectively, were administered locoregionally by CED to dogs with intracranial gliomas to evaluate their safety and preliminary efficacy.

Methods

In this phase I, 3 + 3 dose escalation trial, cytotoxins were infused by CED in 17 dogs with gliomas expressing IL13RA2 or EPHA2 receptors. CED was performed using a shape-fitting therapeutic planning algorithm, reflux-preventing catheters, and real-time intraoperative MRI monitoring. The primary endpoint was to determine the maximum tolerated dose of the cytotoxic cocktail in dogs with gliomas.

Results

Consistent intratumoral delivery of the cytotoxic cocktail was achieved, with a median target coverage of 70% (range, 40–94%). Cytotoxins were well tolerated over a dose range of 0.012–1.278 μg/mL delivered to the target volume (median, 0.099 μg/mL), with no dose limiting toxicities observed. Objective tumor responses, up to 94% tumor volume reduction, were observed in 50% (8/16) of dogs, including at least one dog in each dosing cohort >0.05 μg/mL.

Conclusions

This study provides preclinical data fundamental to the translation of this multireceptor targeted therapeutic approach to the human clinic.

Risk factors for adverse events occurring after recovery from stereotactic brain biopsy in dogs with primary intracranial neoplasia

BACKGROUND

Stereotactic brain biopsy (SBB) allows for histopathologic diagnosis of brain tumors. Adverse events (AE) occur in 5 to 29% of dogs after SBB, but risk factors associated with developing AE are poorly described.

OBJECTIVE

Identify clinicopathologic, diagnostic imaging, or procedural variables that are associated with AE in dogs after SBB.

ANIMALS

Twenty-nine dogs with brain tumors.

METHODS

Retrospective, case-control study. Dogs had laboratory investigations performed before SBB, as well as clinical examinations and diagnostic imaging of the brain before and after SBB. Cases experienced AE after SBB including transient exacerbation of preexisting neurologic deficits, transient new deficits, or permanent neurologic deficits. Controls had SBB performed without AE. Fisher's exact and Student's t tests were used to examine associations between the postulated risk factors and AE.

RESULTS

Adverse events occurred in 8/29 (27%) dogs, and 7/8 AE (88%) were transient. Cases were significantly more likely to have T2W-heterogenous tumors (88 versus 38%; P = .04) and lower platelet counts (194.75 ± 108.32 versus 284.29 ± 68.54 ×103 /mm3 , P = .006). Dogs with gradient echo signal voids present on baseline imaging were significantly more likely to have hemorrhage present after biopsy, and 7/8 (88%) of cases had hemorrhage on imaging after SBB.

CONCLUSION AND CLINICAL IMPORTANCE

Twenty-seven percent of dogs undergoing SBB experience AE, with the majority of AE resolving with 1 week. Platelet counts should be ≥185 000/mm3 to minimize risk of SBB-associated AE. Observation of intracranial hemorrhage after biopsy can have important clinical implications, as this was observed in 88% of dogs with AE.

Transcatheter intra-arterial perfusion (TRIP)-MRI biomarkers help detect immediate response to irreversible electroporation of rabbit VX2 liver tumor

PURPOSE

Irreversible electroporation (IRE) is a nonthermal tissue ablation technique that represents a promising treatment option for unresectable liver tumors, but the effectively treated zone cannot be reliably predicted. We investigate the potential benefit of transcatheter intra-arterial perfusion (TRIP) -MRI for the early noninvasive differentiation of IRE zone from surrounding reversibly electroporated (RE) zone.

METHODS

Seventeen rabbits with VX2 liver tumors were scanned with morphological and contrast-enhanced MRI sequences approximately 30 min after IRE tumor ablation. Quantitative TRIP-MRI perfusion parameters were evaluated in IRE zone and RE zone, defined according to histology. MRI and histology results were compared among zones using Wilcoxon rank-sum tests and correlations were evaluated by Pearson's correlation coefficient.

RESULTS

There were significant differences in area under the curve, time to peak, maximum and late enhancement, wash-in and wash-out rates in the tumor IRE zones compared with the boundary tumor RE zones and untreated tumors. Histology showed significantly fewer tumor cells, microvessels and significantly more apoptosis in tumor IRE zones compared with tumor RE zones (-51%, -66% and +185%, respectively) and untreated tumors (-60%, -67%, and +228%, respectively). A strong correlation was observed between MRI and histology measurements of IRE zones (r = 0.948) and RE zones (r = 0.951).

CONCLUSION

TRIP-MRI demonstrated the potential to detect immediate perfusion changes following IRE liver tumor ablation and effectively differentiate the IRE zone from the surrounding tumor RE zone.

Comparison of direct measurement of intracranial pressures and presumptive clinical and magnetic resonance imaging indicators of intracranial hypertension in dogs with brain tumors

BACKGROUND

Intracranial hypertension (ICH) is often presumptively diagnosed based on clinical or imaging findings. Clinical or imaging surrogates of ICH are not usually validated with reference standard direct intracranial pressure (dICP) recordings.

HYPOTHESES

Dogs with brain magnetic resonance imaging (MRI) or clinical features of presumed ICH would have higher dICP than dogs lacking those features.

ANIMALS

Twenty dogs with gliomas and 3 normal controls.

METHODS

Prospective, convenience study. Dogs were presumptively categorized with normal ICP or ICH from scores generated from described clinical and brain MRI indicators of ICH. dICP was recorded in anesthetized dogs using an intraparenchymal microsensor and compared between groups.

RESULTS

dICP was not different between control (10.4 ± 2.1 mm Hg) and dogs with glioma (15.6 ± 8.3 mm Hg), or between dogs in clinically predicted ICP groups. Compared with dogs with MRI-predicted normal ICP, MRI-predicted ICH dogs had higher dICP (10.3 ± 4.1 versus 19.2 ± 7.9 mm Hg, P = .004), larger tumors (1.45 ± 1.2 versus 5.71 ± 3.03 cm3 , P = .0004), larger optic nerve sheath diameters, and 14/14 (100%) displayed structural anatomical shifts on MRI. At a dICP threshold of 15 mm Hg, the sensitivity of MRI for predicting ICH was 90% and the specificity 69%.

CONCLUSIONS AND CLINICAL RELEVANCE

dICP measurements are feasible in dogs with brain tumors. MRI features including brain herniations, mass effect, and optic nerve size aid in the identification of dogs with ICH. Clinical estimation of ICP did not discriminate between dogs with and without ICH.

Real-Time Impedance Monitoring During Electroporation Processes in Vegetal Tissue Using a High-Performance Generator

Classical application of electroporation is carried out by using fixed protocols that do not clearly assure the complete ablation of the desired tissue. Nowadays, new methods that pursue the control of the treatment by studying the change in impedance during the applied pulses as a function of the electric field are being developed. These types of control seek to carry out the treatment in the fastest way, decreasing undesired effects and treatment time while ensuring the proper tumour ablation. The objective of this research is to determine the state of the treatment by continuously monitoring the impedance by using a novel versatile high-voltage generator and sensor system. To study the impedance dynamics in real time, the use of pulses of reduced voltage, below the threshold of reversible electroporation, is tested to characterise the state-of-the-treatment without interfering with it. With this purpose, a generator that provides both low voltage for sense tissue changes and high voltage for irreversible electroporation (IRE) was developed. In conclusion, the characterisation of the effects of electroporation in vegetal tissue, combined with the real-time monitoring of the state-of-the-treatment, will enable the provision of safer and more effective treatments.

Temperature Dependence of High Frequency Irreversible Electroporation Evaluated in a 3D Tumor Model

Electroporation is a bioelectric phenomenon used to deliver target molecules into cells in vitro and irreversible electroporation (IRE) is an emerging cancer therapy used to treat inoperable tumors in situ. These phenomena are generally considered to be non-thermal in nature. In this study, a 3D tumor model was used to investigate the correlation between temperature and the effectiveness of standard clinical IRE and high frequency (H-FIRE) protocols. It was found for human glioblastoma cells that in the range of 2 to 37 °C the H-FIRE lethal electric field threshold value, which describes the minimum electric field to cause cell death, is highly dependent on temperature. Increasing the initial temperature from 2 to 37 °C resulted in a significant decrease in lethal electric field threshold from 1168 to 507 V/cm and a 139% increase in ablation size for H-FIRE burst treatments. Standard clinical protocol IRE treatments resulted in a decrease in lethal threshold from 485 to 453 V/cm and a 7% increase in ablation size over the same temperature range. Similar results were found for pancreatic cancer cells which indicate that tissue temperature may be a significant factor affecting H-FIRE ablation size and treatment planning in vivo while lower temperatures may be useful in maintaining cell viability for transfection applications.

Optimizing Integrated Electrode Design for Irreversible Electroporation of Implanted Polymer Scaffolds

Irreversible electroporation (IRE) is an emerging technology for non-thermal ablation of solid tumors. This study sought to integrate electrodes into microporous poly(caprolactone) (PCL) scaffolds previously shown to recruit metastasizing cancer cells in vivo in order to facilitate application of IRE to disseminating cancer cells. As the ideal parallel plate geometry would render much of the porous scaffold surface inaccessible to infiltrating cells, numerical modeling was utilized to predict the spatial profile of electric field strength within the scaffold for alternative electrode designs. Metal mesh electrodes with 0.35 mm aperture and 0.16 mm wire diameter established electric fields with similar spatial uniformity as the parallel plate geometry. Composite PCL-IRE scaffolds were fabricated by placing cylindrical porous PCL scaffolds between two PCL dip-coated stainless steel wire meshes. PCL-IRE scaffolds exhibited no difference in cell infiltration in vivo compared to PCL scaffolds. In addition, upon application of IRE in vivo, cells infiltrating the PCL-IRE scaffolds were successfully ablated, as determined by histological analysis 3 days post-treatment. The ability to establish homogeneous electric fields within a biomaterial that can recruit metastatic cancer cells, especially when combined with immunotherapy, may further advance IRE technology beyond solid tumors to the treatment of systemic cancer.

Novel ablation methods for treatment of gliomas

Primary brain tumors are among the deadliest cancers that remain highly incurable. A need exists for new approaches to tumor therapy that can circumvent the blood brain barrier (BBB), target highly resistant tumors and cancer stem-like cells (CSCs) as well create an anti-cancer immunomodulatory environment. Successful treatments may also require a combinatory approach utilizing surgery, chemotherapy, radiation and novel ablation strategies that can both eliminate the bulk tumor and prevent any potential residual CSCs from propagating in the resected tissue. A number of thermal and non-thermal ablation methods have been developed and tested, which have gained much enthusiasm for the treatment of brain tumors. Here we review the most common primary brain tumors and the candidate ablation methods for targeting the tumor and its microenvironment.

The application of point source electroporation and chemotherapy for the treatment of glioma: a randomized controlled rat study

The prognosis of Glioblastoma Multiforme patients is poor despite aggressive therapy. Reasons include poor chemotherapy penetration across the blood-brain barrier and tumor infiltration into surrounding tissues. Here we studied the effects of combined point-source electroporation (EP) and systemic chemotherapy in glioma-bearing rats. 128 rats were studied. Treatment groups were administered systemic Cisplatin/Methotrexate before EP (either 90 or 180 pulses). Control groups were treated by EP, chemotherapy, or no treatment. Tumor volumes were determined by MRI. Tumors growth rates of the EP + Methotrexate group (1.02 ± 0.77) were significantly lower (p < 0.01) than the control (5.2 ± 1.0) 1-week post treatment. No significant difference was found compared to Methotrexate (1.7 ± 0.5). Objective response rates (ORR) were 40% and 57% for the Methotrexate and EP + Methotrexate groups respectively. Tumor growth rates and ORR of the EP + Cisplatin groups (90 pulses 0.98 ± 0.2, 57%, 180 pulses 1.2 ± 0.1, 33%) were significantly smaller than the control (6.4 ± 1.0, p < 0.01, p < 0.02, 0%) and Cisplatin (3.9 ± 1.0, p < 0.04, p < 0.05, 13%) groups. No significant differences were found between the control groups. Increased survival was found in the EP + Cisplatin group, Χ² = 7.54, p < 0.006 (Log Rank). Point-source EP with systemic chemotherapy is a rapid, minimal-invasive treatment that was found to induce significant antineoplastic effects in a rat glioma model.

Companion animal models of neurological disease

Clinical translation of novel therapeutics that improve the survival and quality of life of patients with neurological disease remains a challenge, with many investigational drug and device candidates failing in advanced stage clinical trials. Naturally occurring inherited and acquired neurological diseases, such as epilepsy, inborn errors of metabolism, brain tumors, spinal cord injury, and stroke occur frequently in companion animals, and many of these share epidemiologic, pathophysiologic and clinical features with their human counterparts. As companion animals have a relatively abbreviated lifespan and genetic background, are immunocompetent, share their environment with human caregivers, and can be clinically managed using techniques and tools similar to those used in humans, they have tremendous potential for increasing the predictive value of preclinical drug and device studies. Here, we review comparative features of spontaneous neurological diseases in companion animals with an emphasis on neuroimaging methods and features, illustrate their historical use in translational studies, and discuss inherent limitations associated with each disease model. Integration of companion animals with naturally occurring disease into preclinical studies can complement and expand the knowledge gained from studies in other animal models, accelerate or improve the manner in which research is translated to the human clinic, and ultimately generate discoveries that will benefit the health of humans and animals.

Understanding the role of calcium-mediated cell death in high-frequency irreversible electroporation

High-frequency irreversible electroporation (H-FIRE) is an emerging electroporation-based therapy used to ablate cancerous tissue. Treatment consists of delivering short, bipolar pulses (1-10μs) in a series of 80-100 bursts (1 burst/s, 100μs on-time). Reducing pulse duration leads to reduced treatment volumes compared to traditional IRE, therefore larger voltages must be applied to generate ablations comparable in size. We show that adjuvant calcium enhances ablation area in vitro for H-FIRE treatments of several pulse durations (1, 2, 5, 10μs). Furthermore, H-FIRE treatment using 10μs pulses delivered with 1mM CaCl₂ results in cell death thresholds (771±129V/cm) comparable to IRE thresholds without calcium (698±103V/cm). Quantifying the reversible electroporation threshold revealed that CaCl₂ enhances the permeabilization of cells compared to a NaCl control. Gene expression analysis determined that CaCl₂ upregulates expression of eIFB5 and 60S ribosomal subunit genes while downregulating NOX1/4, leading to increased signaling in pathways that may cause necroptosis. The opposite was found for control treatment without CaCl₂ suggesting cells experience an increase in pro survival signaling. Our study is the first to identify key genes and signaling pathways responsible for differences in cell response to H-FIRE treatment with and without calcium.

Canine Primary Intracranial Cancer: A Clinicopathologic and Comparative Review of Glioma, Meningioma, and Choroid Plexus Tumors

In the dog, primary intracranial neoplasia represents ~2-5% of all cancers and is especially common in certain breeds including English and French bulldogs and Boxers. The most common types of primary intracranial cancer in the dog are meningioma, glioma, and choroid plexus tumors, generally occurring in middle aged to older dogs. Much work has recently been done to understand the characteristic imaging and clinicopathologic features of these tumors. The gross and histologic landscape of these tumors in the dog compare favorably to their human counterparts with many similarities noted in histologic patterns, subtype, and grades. Data informing the underlying molecular abnormalities in the canine tumors have only begun to be unraveled, but reveal similar pathways are mutated between canine and human primary intracranial neoplasia. This review will provide an overview of the clinicopathologic features of the three most common forms of primary intracranial cancer in the dog, delve into the comparative aspects between the dog and human neoplasms, and provide an introduction to current standard of care while also highlighting novel, experimental treatments that may help bridge the gap between canine and human cancer therapies.

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.

Characterization of Ablation Thresholds for 3D-Cultured Patient-Derived Glioma Stem Cells in Response to High-Frequency Irreversible Electroporation

High-frequency irreversible electroporation (H-FIRE) is a technique that uses pulsed electric fields that have been shown to ablate malignant cells. In order to evaluate the clinical potential of H-FIRE to treat glioblastoma (GBM), a primary brain tumor, we have studied the effects of high-frequency waveforms on therapy-resistant glioma stem-like cell (GSC) populations. We demonstrate that patient-derived GSCs are more susceptible to H-FIRE damage than primary normal astrocytes. This selectivity presents an opportunity for a degree of malignant cell targeting as bulk tumor cells and tumor stem cells are seen to exhibit similar lethal electric field thresholds, significantly lower than that of healthy astrocytes. However, neural stem cell (NSC) populations also exhibit a similar sensitivity to these pulses. This observation may suggest that different considerations be taken when applying these therapies in younger versus older patients, where the importance of preserving NSC populations may impose different restrictions on use. We also demonstrate variability in threshold among the three patient-derived GSC lines studied, suggesting the need for personalized cell-specific characterization in the development of potential clinical procedures. Future work may provide further useful insights regarding this patient-dependent variability observed that could inform targeted and personalized treatment.

Diagnostic accuracy of stereotactic brain biopsy for intracranial neoplasia in dogs: Comparison of biopsy, surgical resection, and necropsy specimens

Background

Stereotactic brain biopsy (SBB) is a technique that allows for definitive diagnosis of brain lesions. Little information is available regarding the diagnostic utility of SBB in dogs with intracranial diseases.

Objective

To investigate the diagnostic accuracy (DA) of SBB in dogs with brain tumors.

Animals

Thirty‐one client‐owned dogs that underwent SBB followed by surgical resection or necropsy examinations.

Methods

Retrospective observational study. Two pathologists blinded to SBB and reference standard diagnoses reviewed histologic specimens and typed and graded tumors according to World Health Organization and revised canine glioma classification criteria. Agreement between tumor type and grade from SBB were compared to reference standards and assessed using kappa statistics. Patient and technical factors associated with agreement also were examined.

Results

Stereotactic brain biopsy specimens were obtained from 24 dogs with gliomas and 7 with meningiomas. Tumor type agreement between SBB and the reference standard was observed in 30/31 cases (κ = 0.95). Diagnostic concordance was perfect for meningiomas. Grade agreement among gliomas was observed in 18/23 cases (κ = 0.47). Stereotactic brain biopsy underrepresented the reference standard glioma grade in cases with disagreement. The DA of SBB was 81%, with agreement noted in 56/69 biopsy samples. Smaller tumors and fewer SBB specimens obtained were significantly associated with diagnostic discordance.

Conclusions and Clinical Importance

The DA of SBB readily allows for the diagnosis of common brain tumors in dogs. Although glioma grade discordance was frequent, diagnoses obtained from SBB are sufficient to currently inform therapeutic decisions. Multiple SBB specimens should be collected to maximize DA.

Application of Pulsed Electric Fields to Cancer Therapy

This review covers the use of pulsed electric fields in cancer therapy. It is organized into three sections based on pulse length, millisecond domain, microsecond domain, and nanosecond domain. The predominant application of pulsed electric fields is the modification of the permeability of cellular membranes, sometimes referred to as electroporation. This has been used in many different ways for cancer treatment. These include introducing genes into the tumor cells to activate an immune response, introducing poisons into the tumor cells, initiating necrosis using irreversible electroporation, and initiating immunogenic cell death with nanopulse stimulation.

Immunohistochemical Characterization of Procaspase-3 Overexpression as a Druggable Target With PAC-1, a Procaspase-3 Activator, in Canine and Human Brain Cancers

Gliomas and meningiomas are the most common brain neoplasms affecting both humans and canines, and identifying druggable targets conserved across multiple brain cancer histologies and comparative species could broadly improve treatment outcomes. While satisfactory cure rates for low grade, non-invasive brain cancers are achievable with conventional therapies including surgery and radiation, the management of non-resectable or recurrent brain tumors remains problematic and necessitates the discovery of novel therapies that could be accelerated through a comparative approach, such as the inclusion of pet dogs with naturally-occurring brain cancers. Evidence supports procaspase-3 as a druggable brain cancer target with PAC-1, a pro-apoptotic, small molecule activator of procaspase-3 that crosses the blood-brain barrier. Procaspase-3 is frequently overexpressed in malignantly transformed tissues and provides a preferential target for inducing cancer cell apoptosis. While preliminary evidence supports procaspase-3 as a viable target in preclinical models, with PAC-1 demonstrating activity in rodent models and dogs with spontaneous brain tumors, the broader applicability of procaspase-3 as a target in human brain cancers, as well as the comparability of procaspase-3 expressions between differing species, requires further investigation. As such, a large-scale validation of procaspase-3 as a druggable target was undertaken across 651 human and canine brain tumors. Relative to normal brain tissues, procaspase-3 was overexpressed in histologically diverse cancerous brain tissues, supporting procaspase-3 as a broad and conserved therapeutic target. Additionally, procaspase-3 expressing glioma and meningioma cell lines were sensitive to the apoptotic effects of PAC-1 at biologically relevant exposures achievable in cancer patients. Importantly, the clinical relevance of procaspase-3 as a potential prognostic variable was demonstrated in human astrocytomas of variable histologic grades and associated clinical outcomes, whereby tumoral procaspase-3 expression was negatively correlated with survival; findings which suggest that PAC-1 might provide the greatest benefit for patients with the most guarded prognoses.

High-Frequency Irreversible Electroporation for Intracranial Meningioma: A Feasibility Study in a Spontaneous Canine Tumor Model

High-frequency irreversible electroporation is a nonthermal method of tissue ablation that uses bursts of 0.5- to 2.0-microsecond bipolar electric pulses to permeabilize cell membranes and induce cell death. High-frequency irreversible electroporation has potential advantages for use in neurosurgery, including the ability to deliver pulses without inducing muscle contraction, inherent selectivity against malignant cells, and the capability of simultaneously opening the blood–brain barrier surrounding regions of ablation. Our objective was to determine whether high-frequency irreversible electroporation pulses capable of tumor ablation could be delivered to dogs with intracranial meningiomas. Three dogs with intracranial meningiomas were treated. Patient-specific treatment plans were generated using magnetic resonance imaging-based tissue segmentation, volumetric meshing, and finite element modeling. Following tumor biopsy, high-frequency irreversible electroporation pulses were stereotactically delivered in situ followed by tumor resection and morphologic and volumetric assessments of ablations. Clinical evaluations of treatment included pre- and posttreatment clinical, laboratory, and magnetic resonance imaging examinations and adverse event monitoring for 2 weeks posttreatment. High-frequency irreversible electroporation pulses were administered successfully in all patients. No adverse events directly attributable to high-frequency irreversible electroporation were observed. Individual ablations resulted in volumes of tumor necrosis ranging from 0.25 to 1.29 cm³. In one dog, nonuniform ablations were observed, with viable tumor cells remaining around foci of intratumoral mineralization. In conclusion, high-frequency irreversible electroporation pulses can be delivered to brain tumors, including areas adjacent to critical vasculature, and are capable of producing clinically relevant volumes of tumor ablation. Mineralization may complicate achievement of complete tumor ablation.

Plasma membrane depolarization and permeabilization due to electric pulses in cell lines of different excitability

In electroporation-based medical treatments, excitable tissues are treated, either intentionally (irreversible electroporation of brain cancer, gene electrotransfer or ablation of the heart muscle, gene electrotransfer of skeletal muscles), or unintentionally (excitable tissues near the target area). We investigated how excitable and non-excitable cells respond to electric pulses, and if electroporation could be an effective treatment of the tumours of the central nervous system. For three non-excitable and one excitable cell line, we determined a strength-duration curve for a single pulse of 10ns-10ms. The threshold for depolarization decreased with longer pulses and was higher for excitable cells. We modelled the response with the Lapicque curve and the Hodgkin-Huxley model. At 1μs a plateau of excitability was reached which could explain why high-frequency irreversible electroporation (H-FIRE) electroporates but does not excite cells. We exposed cells to standard electrochemotherapy parameters (8×100μs pulses, 1Hz, different voltages). Cells behaved similarly which indicates that electroporation most probably occurs at the level of lipid bilayer, independently of the voltage-gated channels. These results could be used for optimization of electric pulses to achieve maximal permeabilization and minimal excitation/pain sensation. In the future, it should be established whether the in vitro depolarization correlates to nerve/muscle stimulation and pain sensation in vivo.

Consensus recommendations on standardized magnetic resonance imaging protocols for multicenter canine brain tumor clinical trials

The National Cancer Institute Comparative Brain Tumor Consortium, Patient Outcomes Working Group, propose a consensus document in support of standardized magnetic resonance imaging protocols for canine brain tumor clinical trials. The intent of this manuscript is to address the widely acknowledged need to ensure canine brain tumor imaging protocols are relevant and have sufficient equivalency to translate to human studies such that: (1) multi-institutional studies can be performed with minimal inter-institutional variation, and (2) imaging protocols are consistent with human consensus recommendations to permit reliable translation of imaging data to human clinical trials. Consensus recommendations include pre- and postcontrast three-dimensional T1-weighted images, T2-weighted turbo spin echo in all three planes, T2*-weighted gradient recalled echo, T2-weighted fluid attenuated inversion recovery, and diffusion weighted imaging/diffusion tensor imaging in transverse plane; field of view of ≤150 mm; slice thickness of ≤2 mm, matrix ≥ 256 for two-dimensional images, and 150 or 256 for three-dimensional images.

First Human Trial of High-Frequency Irreversible Electroporation Therapy for Prostate Cancer

Irreversible electroporation, as a nonthermal therapy of prostate cancer, has been used in clinic for several years. The mechanism of irreversible electroporation ablation is thermal independent; thus, the main structures (eg, rectum, urethra, and neurovascular bundle) in prostate are spared during the treatment, which leads to the retention of prostate function. However, various clinical trials have shown that muscle contractions occur during this therapy, which warrants deep muscle anesthesia. Use of high-frequency bipolar pulses has been proposed to reduce muscle contractions during treatment, which has already triggered a multitude of studies at the cellular and animal scale. In this study, we first investigated the efficacy and safety of high-frequency bipolar pulses in human prostate cancer ablation. There are 40 male patients with prostate cancer aged between 51 and 85 years involved in this study. All patients received 250 high-frequency bipolar pulse bursts with the repeat frequency of 1 Hz. Each burst comprised 20 individual pulses of 5 microseconds, so one burst total energized time was 100 microseconds. The number of the electrodes ranged 2 to 6, depending on tumor size. A small amount of muscle relaxant was still needed, so there were no visible muscle contractions during the pulse delivery process. Four weeks after treatment, it was found that the ablation margins were distinct in magnetic resonance imaging scans, and the prostate capsule and urethra were retained. Eight patients underwent radical prostatectomy for pathological analysis after treatment, and the results of hematoxylin and eosin staining revealed that the urethra and major vasculature in prostate have been preserved. By overlaying the electric field contour on the ablation zone, the electric field lethality threshold is determined to be 522 ± 74 V/cm. This study is the first to validate the feasibility of tumor ablation by high-frequency bipolar pulses and provide valuable experience of irreversible electroporation in clinical applications.

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping

Unlocking the secrets of the brain is a task fraught with complexity and challenge - not least due to the intricacy of the circuits involved. With advancements in the scale and precision of scientific technologies, we are increasingly equipped to explore how these components interact to produce a vast range of outputs that constitute function and disease. Here, an insight is offered into key areas in which the marriage of neuroscience and nanotechnology has revolutionized the industry. The evolution of ever more sophisticated nanomaterials culminates in network-operant functionalized agents. In turn, these materials contribute to novel diagnostic and therapeutic strategies, including drug delivery, neuroprotection, neural regeneration, neuroimaging and neurosurgery. Further, the entrance of nanotechnology into future research arenas including optogenetics, molecular/ion sensing and monitoring, and piezoelectric effects is discussed. Finally, considerations in nanoneurotoxicity, the main barrier to clinical translation, are reviewed, and direction for future perspectives is provided.

A microfluidic model of the blood-brain barrier to study permeabilization by pulsed electric fields

Pulsed electric fields interact with the blood-brain barrier (BBB) and have been shown to increase the BBB permeability under some pulsing regimes. Pulsed electric fields may enhance drug delivery to the brain by disrupting the integrity of the BBB and allowing otherwise impermeable drugs to reach target areas. Microfluidic, in vitro models offer an alternative platform for exploring the impact of pulsed electric fields on the BBB because they create physiologically relevant microenvironments and eliminate the confounding variables of animal studies. We developed a microfluidic platform for real-time measurement of BBB permeability pre- and post-treatment with pulsed electric fields. Permeability is measured optically by the diffusion of fluorescent tracers across a monolayer of human cerebral microcapillary endothelial cells (hCMECs) cultured on a permeable membrane. We found that this device is able to capture real-time permeability of hCMEC monolayers for both reversible and irreversible electroporation pulsing regimes. Furthermore, preliminary testing of deep brain stimulation pulsing regimes reveals possible impacts on BBB integrity. This device will enable future studies of pulsed electric field regimes for improved understanding of BBB permeabilization.

The Feasibility of Enhancing Susceptibility of Glioblastoma Cells to IRE Using a Calcium Adjuvant

Irreversible electroporation (IRE) is a cellular ablation method used to treat a variety of cancers. IRE works by exposing tissues to pulsed electric fields which cause cell membrane disruption. Cells exposed to lower energies become temporarily permeable while greater energy exposure results in cell death. For IRE to be used safely in the brain, methods are needed to extend the area of ablation without increasing applied voltage, and thus, thermal damage. We present evidence that IRE used with adjuvant calcium (5 mM CaCl₂) results in a nearly twofold increase in ablation area in vitro compared to IRE alone. Adjuvant 5 mM CaCl₂ induces death in cells reversibly electroporated by IRE, thereby lowering the electric field thresholds required for cell death to nearly half that of IRE alone. The calcium-induced death response of reversibly electroporated cells is confirmed by electrochemotherapy pulses which also induced cell death with calcium but not without. These findings, combined with our numerical modeling, suggest the ability to ablate up to 3.2× larger volumes of tissue in vivo when combining IRE and calcium. The ability to ablate a larger volume with lowered energies would improve the efficacy and safety of IRE therapy.

Treatment of Cancer In Vitro Using Radiation and High-Frequency Bursts of Submicrosecond Electrical Pulses

High-frequency irreversible electroporation (H-FIRE) is an emerging cancer therapy, which uses bursts of short duration, alternating polarity, high-voltage electrical pulses to focally ablate tumors. Here, we present a preliminary investigation of the combinatorial effects of H-FIRE and ionizing radiation. In vitro cell cultures were exposed to bursts of 500 ns pulses and single radiation doses of 2 or 20 Gy then analyzed for 14 days. H-FIRE and radiation therapy (RT) appear to induce different delayed cell death mechanisms and in all treatment groups combinatorial therapy resulted in lower overall viabilities. These results indicate that in vivo investigation of the antitumor efficacy of combined H-FIRE and RT is warranted.

Bipolar Microsecond Pulses and Insulated Needle Electrodes for Reducing Muscle Contractions During Irreversible Electroporation

OBJECTIVE

To minimize the effect of muscle contractions during irreversible electroporation (IRE), this paper attempts to research the ablation effect and muscle contractions by applying high-frequency IRE (H-FIRE) ablation to liver tissue in vivo.

METHODS

An insulated needle electrode was produced by painting an insulating coating on the outer surface of the needle electrode tip. A series of experiments were conducted using insulated needle electrodes and traditional needle electrodes to apply H-FIRE pulses and traditional monopolar IRE pulses to rabbit liver tissues. The finite element model of the rabbit liver tissue was established to determine the lethal thresholds of H-FIRE in liver tissues. Muscle contractions were measured by an accelerometer.

RESULTS

With increased constitutive pulse width and pulse voltage, the ablation area and muscle contraction strength are also increased, which can be used to optimize the ablation parameters of H-FIRE. Under the same pulse parameters, the ablation areas are similar for the two types of electrodes, and the ablation region has a clear boundary. H-FIRE and insulated needle electrodes can mitigate the extent of muscle contractions. The lethal thresholds of H-FIRE in rabbit liver tissues were determined.

CONCLUSION

This paper describes the relationships between the ablation area, muscle contractions, and pulse parameters; the designed insulated needle electrodes can be used in IRE for reducing muscle contraction.

SIGNIFICANCE

The study provides guidance for treatment planning and reducing muscle contractions in the clinical application of H-FIRE.

High-Frequency Irreversible Electroporation: Safety and Efficacy of Next-Generation Irreversible Electroporation Adjacent to Critical Hepatic Structures

Irreversible electroporation (IRE) is a nonthermal ablation modality employed to induce in situ tissue-cell death. This study sought to evaluate the efficacy of a novel high-frequency IRE (H-FIRE) system to perform hepatic ablations across, or adjacent to, critical vascular and biliary structures. Using ultrasound guidance H-FIRE electrodes were placed across, or adjacent to, portal pedicels, hepatic veins, or the gall bladder in a porcine model. H-FIRE pulses were delivered (2250 V, 2-5-2 pulse configuration) in the absence of cardiac synchronization or intraoperative paralytics. Six hours after H-FIRE the liver was resected and analyzed. Nine ablations were performed in 3 separate experimental groups (major vessels straddled by electrodes, electrodes placed adjacent to major vessels, electrodes placed adjacent to gall bladder). Average ablation time was 290 ± 63 seconds. No electrocardiogram abnormalities or changes in vital signs were observed during H-FIRE. At necropsy, no vascular damage, coagulated-thermally desiccated blood vessels, or perforated biliary structures were noted. Histologically, H-FIRE demonstrated effective tissue ablation and uniform induction of apoptotic cell death in the parenchyma independent of vascular or biliary structure location. Detailed microscopic analysis revealed minor endothelial damage within areas subjected to H-FIRE, particularly in regions proximal to electrode insertion. These data indicate H-FIRE is a novel means to perform rapid, reproducible IRE in liver tissue while preserving gross vascular/biliary architecture. These characteristics raise the potential for long-term survival studies to test the viability of this technology toward clinical use to target tumors not amenable to thermal ablation or resection.

Asymmetric Waveforms Decrease Lethal Thresholds in High Frequency Irreversible Electroporation Therapies

Irreversible electroporation (IRE) is a promising non-thermal treatment for inoperable tumors which uses short (50-100 μs) high voltage monopolar pulses to disrupt the membranes of cells within a well-defined volume. Challenges with IRE include complex treatment planning and the induction of intense muscle contractions. High frequency IRE (H-FIRE) uses bursts of ultrashort (0.25-5 μs) alternating polarity pulses to produce more predictable ablations and alleviate muscle contractions associated with IRE. However, H-FIRE generally ablates smaller volumes of tissue than IRE. This study shows that asymmetric H-FIRE waveforms can be used to create ablation volumes equivalent to standard IRE treatments. Lethal thresholds (LT) of 505 V/cm and 1316 V/cm were found for brain cancer cells when 100 μs IRE and 2 μs symmetric H-FIRE waveforms were used. In contrast, LT as low as 536 V/cm were found for 2 μs asymmetric H-FIRE waveforms. Reversible electroporation thresholds were 54% lower than LTs for symmetric waveforms and 33% lower for asymmetric waveforms indicating that waveform symmetry can be used to tune the relative sizes of reversible and irreversible ablation zones. Numerical simulations predicted that asymmetric H-FIRE waveforms are capable of producing ablation volumes which were 5.8-6.3x larger than symmetric H-FIRE waveforms indicating that in vivo investigation of asymmetric waveforms is warranted.