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

Abstract

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.

Keywords: cancer; companion animals; electrochemotherapy; gene electrotransfer; gene therapy; immune response; tumor.

Figure 1

A case of a canine sebaceous gland carcinoma in a 4-year-old female cocker spaniel. In (a), the initial presentation, with a large lesion of 15 × 6.5 cm containing multiple nodules and ulcers. Only 20% of the tumors were treated with Electrochemotherapy (ECT) due to the large extension and spread of the disease, intending to repeat more sessions in the future. In (b), the patient achieved a complete response within 12 weeks of a single ECT session. Fifteen months later, the patient remains free of disease (data not published).

Figure 2

A case of a golden retriever with a fibrosarcoma, in (a), before the ECT. In (b), the patient obtained a partial response after the treatment. In contrast to the natural evolution of the disease, it remained stable without any other treatment after two years (data not published).

Figure 3

In this case, a horse with a sarcoid in the eyelid. In (a), the day the ECT was performed. In (b), thirty days after the ECT, the tumor experiences an increase in its size due to swelling. In (c), after a single session of ECT, a complete response was obtained. The animal remained disease-free for 400 days, and up to the date of the writing of this work (data not published).

Figure 4

Map of Latin America. Orange spots indicate countries where ECT is performed as a standard of care in veterinary medicine.

Figure 5

Different electrodes for ECT in veterinary medicine. In (a), a six-needle electrode. In (b), a four-needle electrode using thin-needles. In (c), a 90 degrees handle for the thin-needles electrode. In (d), an electrode for treating nasal duct. In (e), on top, disposable-needles, at the bottom, plates electrode that can be attached to the handles. Courtesy of BIOTEX SRL.