Electroporation in veterinary oncology

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.

A linear SARS-CoV-2 DNA vaccine candidate reduces virus shedding in ferrets

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has caused more than 760 million cases and over 6.8 million deaths as of March 2023. Vaccination has been the main strategy used to contain the spread of the virus and to prevent hospitalizations and deaths. Currently, two mRNA-based vaccines and one adenovirus-vectored vaccine have been approved and are available for use in the U.S. population. The versatility, low cost, and rapid production of DNA vaccines provide important advantages over other platforms. Additionally, DNA vaccines efficiently induce both B- and T-cell responses by expressing the antigen within transfected host cells, and the antigen, after being processed into peptides, can associate with MHC class I or II of antigen-presenting cells (APCs) to stimulate different T cell responses. However, the efficiency of DNA vaccination needs to be improved for use in humans. Importantly, in vivo DNA delivery combined with electroporation (EP) has been used successfully in the field of veterinary oncology, resulting in high rates of response after electrochemotherapy. Here, we evaluate the safety, immunogenicity, and protective efficacy of a novel linear SARS-CoV-2 DNA vaccine candidate delivered by intramuscular injection followed by electroporation (Vet-ePorator™) in ferrets. The linear SARS-CoV-2 DNA vaccine candidate did not cause unexpected side effects. Additionally, the vaccine elicited neutralizing antibodies and T cell responses on day 42 post-immunization using a low dose of the linear DNA construct in a prime-boost regimen. Most importantly, vaccination significantly reduced shedding of infectious SARS-CoV-2 through oral and nasal secretions in a ferret model.

Effective Penetration of a Liposomal Formulation of Bleomycin through Ex-Vivo Skin Explants from Two Different Species

Bleomycin is a chemotherapy agent that, when administered systemically, can cause severe pulmonary toxicity. Bleosome is a novel formulation of bleomycin encapsulated in ultra-deformable (UD) liposomes that may be applicable as a topical chemotherapy for diseases such as non-melanoma skin cancer. To date, the ability of Bleosome to effectively penetrate through the skin has not been evaluated. In this study, we investigated the ability of Bleosome to penetrate through ex vivo skin explants from dogs and horses. We visualized the penetration of UD liposomes through the skin by transmission electron microscopy. However, to effectively image the drug itself we fluorescently labeled bleomycin prior to encapsulation within liposomes and utilized multiphoton microscopy. We showed that UD liposomes do not penetrate beyond the stratum corneum, whereas bleomycin is released from UD liposomes and can penetrate to the deeper layers of the epidermis. This is the first study to show that Bleosome can effectively penetrate through the skin. We speculate that UD liposomes are penetration enhancers in that UD liposomes carry bleomycin through the outer skin to the stratum corneum and then release the drug, allowing diffusion into the deeper layers. Our results are comparative in dogs and horses and warrant further studies on the efficacy of Bleosome as topical treatment.

Results of Dynamic Contrast-Enhanced Ultrasound Correlate With Treatment Outcome in Canine Neoplasia Treated With Electrochemotherapy and Interleukin-12 Plasmid Electrotransfer

Electrochemotherapy (ECT) and/or gene electrotransfer of plasmid DNA encoding interleukin-12 (GET pIL-12) are effective treatments for canine cutaneous, subcutaneous, and maxillofacial tumors. Despite the clinical efficacy of the combined treatments of ECT and GET, data on parameters that might predict the outcome of the treatments are still lacking. This study aimed to investigate whether dynamic contrast-enhanced ultrasound (DCE-US) results of subcutaneous tumors differ between tumors with complete response (CR) and tumors without complete response (non-CR) in dogs treated with ECT and GET pIL-12. Eight dogs with a total of 12 tumor nodules treated with ECT and GET pIL-12 were included. DCE-US examinations were performed in all animals before and immediately after therapy as well as 8 h and 1, 3, and 7 days later. Clinical follow-up examinations were performed 7 and 14 days, 1 and 6 months, and 1 year after treatment. Numerous significant differences in DCE-US parameters were noted between tumors with CR and non-CR tumors; perfusion and perfusion heterogeneity were lower in CR tumors than in non-CR tumors. Therefore, studies with larger numbers of patients are needed to investigate whether DCE-US results can be used to predict treatment outcomes and to make effective decisions about the need for repeated therapy or different treatment combinations in individual patients.

Electroporation-Based Treatments in Small Animal Veterinary Oral and Maxillofacial Oncology

Electroporation is a method of inducing an increase in permeability of the cell membrane through the application of an electric field and can be used as a delivery method for introducing molecules of interest (e.g., chemotherapeutics or plasmid DNA) into cells. Electroporation-based treatments (i.e., electrochemotherapy, gene electrotransfer, and their combinations) have been shown to be safe and effective in veterinary oncology, but they are currently mostly recommended for the treatment of those solid tumors for which clients have declined surgery and/or radiotherapy. Published data show that electroporation-based treatments are also safe, simple, fast and cost-effective treatment alternatives for selected oral and maxillofacial tumors, especially small squamous cell carcinoma and malignant melanoma tumors not involving the bone in dogs. In these patients, a good local response to treatment is expected to result in increased survival time with good quality of life. Despite emerging evidence of the clinical efficacy of electroporation-based treatments for oral and maxillofacial tumors, further investigation is needed to optimize treatment protocols, improve clinical data reporting and better understand the mechanisms of patients' response to the treatment.

Design and Characterization of a Minimally Invasive Bipolar Electrode for Electroporation

OBJECTIVE

To test a new bipolar electrode for electroporation consisting of a single minimally invasive needle.

METHODS

A theoretical study was performed by using Comsol Multiphysics^® software. The prototypes of electrode have been tested on potatoes and pigs, adopting an irreversible electroporation protocol. Different applied voltages and different geometries of bipolar electrode prototype have been evaluated.

RESULTS

Simulations and pre-clinical tests have shown that the volume of ablated area is mainly influenced by applied voltage, while the diameter of the electrode had a lesser impact, making the goal of minimal-invasiveness possible. The conductive pole's length determined an increase of electroporated volume, while the insulated pole length inversely affects the electroporated volume size and shape; when the insulated pole length decreases, a more regular shape of the electric field is obtained. Moreover, the geometry of the electrode determined a different shape of the electroporated volume. A parenchymal damage in the liver of pigs due to irreversible electroporation protocol was observed.

CONCLUSION

The minimally invasive bipolar electrode is able to treat an electroporated volume of about 10 mm in diameter by using a single-needle electrode. Moreover, the geometry and the electric characteristics can be selected to produce ellipsoidal ablation volumes.

Electroporation as the Immunotherapy Strategy for Cancer in Veterinary Medicine: State of the Art in Latin America

Electroporation is a technology that increases cell membrane permeability by the application of electric pulses. Electrochemotherapy (ECT), the best-known application of electroporation, is a very effective local treatment for tumors of any histology in human and veterinary medicine. It induces a local yet robust immune response that is responsible for its high effectiveness. Gene electrotransfer (GET), used in research to produce a systemic immune response against cancer, is another electroporation-based treatment that is very appealing for its effectiveness, low cost, and simplicity. In this review, we present the immune effect of electroporation-based treatments and analyze the results of the vast majority of the published papers related to immune response enhancement by gene electrotransfer in companion animals with spontaneous tumors. In addition, we present a brief history of the initial steps and the state of the art of the electroporation-based treatments in Latin America. They have the potential to become an essential form of immunotherapy in the region. This review gives insight into the subject and helps to choose promising research lines for future work; it also helps to select the adequate treatment parameters for performing a successful application of this technology.

Paclitaxel-in-liposome-in-bacteria for inhalation treatment of primary lung cancer

Bacterial therapy is emerging for the treatment of cancers though some scientific and clinical problems have not been addressed. Here, a live drug-loaded carrier, paclitaxel-in-liposome-in-bacteria (LPB), was prepared for inhalation treatment of primary lung cancer, where liposomal paclitaxel (LP) was highly effectively internalized into bacteria (E. coli or L. casei) to get LP-in-E. coli (LPE) or LP-in-L. casei (LPL) by electroporation that had no influence on the growth of these bacteria. Bacteria, LP, the simple mixture of LP and bacteria, and LPB remarkably inhibited the proliferation of A549 lung cancer cells, where LPE was the strongest one. Drug-loaded bacteria delivered the cargos into the cells more quickly than the mixture of drugs and bacteria and the cargos alone. LPE also showed the highest anticancer effect on the rat primary lung cancer among them with the downregulation of VEGF and HIF-1α and the improvement of cancer cell apoptosis after intratracheal administration. Moreover, the bacterial formulations significantly enhanced the expressions of immune markers (TNF-α, IL-4, and IFN-γ) and immune cells (leukocytes and neutrophils). LPB showed much higher bacterial distribution in the lung than other organs after intratracheal administration. LPB is a promising medicine for inhalation treatment of primary lung cancer.

Health-related quality of life in dogs treated with electrochemotherapy and/or interleukin-12 gene electrotransfer

The aim of this study was to evaluate the owners' perception of health‐related quality of life (HRQoL) of dogs after treatment with electrochemotherapy (ECT) alone or combined with interleukin‐12 gene electrotransfer (IL‐12 GET) and/or surgery. The owners of 44 dogs with histologically different tumours were offered the »Cancer Treatment Form« at least one month after treatment. The owners assessed their dogs’ quality of life (QoL) after treatment as good (mean 7.4) (from 1–very poor to 10–excellent) and the general health compared with the initial diagnosis of cancer as improving (mean 3.9) (from 1–worse to 5–better). The assessment of the current QoL was better within the group of dogs treated with non‐invasive treatment (ECT and/or IL‐12 GET only), compared with those that received invasive treatment, where, in addition to ECT and/or IL‐12 GET, surgery was performed (p < .05). The owners of dogs that achieved an objective response (OR) to the treatment assessed the QoL as significantly better compared with those whose dogs did not respond to the treatment (p < .05). The majority of the owners (86.4%) would opt for the therapy again, regardless of the financial costs. In conclusion, the results of this study demonstrate that the majority of the owners of dogs assessed their dogs’ QoL as good and felt that it improved after the treatment, especially in dogs, treated with non‐invasive treatment and in those that responded to the treatment. This supports further use of ECT and IL‐12 GET as suitable methods for the treatment of selected tumours in veterinary medicine.

Computer simulation of commercial conductive gels and their application to increase the safety of electrochemotherapy treatment

Electrochemotherapy (ECT) exploits the phenomenon of electroporation, which is the increase of cell permeability through the application of an electrical field. This technique is applied in medical centers in Europe and in veterinary clinics in Europe, Brazil, and Argentina. ECT treatment requires a minimum electric field and anti-cancer drugs (e.g., bleomycin). Irregularly shaped tumors may induce ECT treatment failure because of irregular electric field distribution. Conductive gels have been suggested as a means to increase the homogeneity of the electrical field distribution. The aim of this work was to evaluate if commercial conductive gels could increase the safety of ECT. A veterinary case study of ECT in a dog provided the tumor dimensions for the numerical model. Electrode displacement and commercial conductive gels were simulated to determine if they improved ECT treatments. We conclude that a commercial gel having a conductivity of 0.2 S/m when used in combination with effective treatment planning may improve the outcome of electrochemotherapy procedures.

Calcium electroporation: The bioelectrochemical treatment of spontaneous equine skin tumors results in a local necrosis

Electrochemotherapy (ECT) is an anticancer bioelectrochemical therapy where electrical field pulses (electropermeabilization) increase intracellular concentration of antitumor drugs. The procedure is very effective against skin tumors. The restrictive regulations concerning anticancer drugs in veterinary medicine limit use of ECT. Electroporation with calcium (Electroporation Calcium Therapy)(ECaT) was proved to be effective in vivo on induced tumors in laboratory animals. This study evaluated the effects of ECaT in equine sarcoids (spontaneous skin tumors) on an animal cohort. Pulse parameters for ECaT were choosen for using skin contact electrodes. ECaT was applied under general anesthesia. The tumors were removed at different days after the treatment and analyzed by histology. The study assessed the volume fraction of necrosis that was >50% for 9 of 13 sarcoids. Sixteen sarcoids in 10 horses were treated with ECaT. Macroscopic changes (a crust) were observed in 14/16 tumors. The main microscopic changes were necrosis, ulceration,hemorrhages, calcifications and thrombosis. The adverse effect was an inflammatory local reaction. Surrounding tissues were not affected. This targeted effect can be explained by its control by the field distribution in the tissue and on the interstitial diffusion of the injected Ca²⁺.

Plasma Bleomycin Concentrations during Electrochemotherapeutic Treatment of Fibropapillomas in Green Turtles Chelonia mydas

Fibropapillomatosis of sea turtles is traditionally treated with surgical debulking techniques that are often associated with prolonged healing and tumor recurrence. Electrochemotherapy was recently described for green turtles Chelonia mydas and can be an alternative to surgery and even general anesthesia. The objectives of this study were to replicate an electrochemotherapy protocol from a previous report and add plasma bleomycin analysis to the treatment. After bleomycin injection into similarly sized tumors of two green turtles and immediate electroporation at two time points, plasma bleomycin reached detectable concentrations that were considerably lower than those found in human studies. At 3 months posttherapy, no healing complications or recurrences were encountered and only scar tissue remained. This study adds further support that electrochemotherapy with bleomycin has the potential to be used as an effective alternative treatment for this complex disease.

A combination of electrochemotherapy, gene electrotransfer of plasmid encoding canine IL-12 and cytoreductive surgery in the treatment of canine oral malignant melanoma

The aim of this study was to evaluate the safety and efficacy of the combination of electrochemotherapy (ECT) with bleomycin and gene electrotransfer (GET) of plasmid encoding canine interleukin 12 (IL-12) for the treatment of canine oral malignant melanoma (OMM). Our focus was to determine the effect of the treatment on achieving local tumor control and stimulation of an antitumor immune response. Nine dogs with histologically confirmed OMM stage I to III were included in a prospective, non-randomized study. The dogs were treated with a combination of cytoreductive surgery, ECT and IL-12 GET, which was repeated up to five times, depending on the clinical response to the treatment, evaluated according to the follow-up protocol (7, 14 and 28 days after, the last treatment). One month after treatment, the objective response (OR) rate was 67% (6/9). Median survival time (MST) was 6 months and, even though the disease progressed in 8/9 patients at the end of the observation period (2 to 22 months), four animals were euthanized due to tumor-unrelated reasons. In addition, we observed a decline in the percentage of regulatory T cells (Treg) in the peripheral blood in the course of the treatment, which could be attributed to a systemic antitumor response to IL-12 GET. The results of this study suggest that a combination of ECT and IL-12 GET may be beneficial for dogs with OMM, especially when other treatment approaches are not acceptable due to their invasiveness or cost.

Minimally Invasive Electrochemotherapy Procedure for Treating Nasal Duct Tumors in Dogs using a Single Needle Electrode

Background

Nasal cavity tumors are usually diagnosed late, when they already have infiltrated adjacent tissues thus requiring very aggressive treatments with serious side effects. Here we use electrochemotherapy (ECT), a well demonstrated treatment modality for superficial tumors.

Materials and methods

In the case of deep-seated tumors, the main limitation of ECT is reaching the tumor with an appropriate electric field. To overcome this limitation we introduce the single needle electrode (SiNE), a minimally invasive device that can deliver an appropriate electric field with a simple procedure. Twenty-one canine patients with spontaneous tumors were selected, eleven were treated using the SiNE with ECT, and ten with surgery plus adjuvant chemotherapy as a control group.

Results

In the SiNE group, 27% achieved a complete response, 64% had a partial response, and 9% had a stable disease. This means that 91% of objective responses were obtained. The mean overall survival was 16.86 months (4–32 months, median 16.5 months), with a survival rate significantly higher (p = 0.0008) when compared with control group. The only side effect observed was the inflammation of the treated nasal passage, which was controlled with corticosteroid therapy for one week. One year after the treatment, 60% of the canine of the SiNE group vs. 10% of the control group remained alive, and after the 32 months follow-up, the survival rate were 30% and 0%, respectively.

Conclusions

ECT with the SiNE can be safely used in canine to treat nasal tumors with encouraging results.