OI Ljubljana

Monitoring of the clinical and immune response to improve the outcome of combined electrochemotherapy and IL-12 gene therapy in dogs with spontaneous peripheral tumours


Immune therapies, based on the encouraging results of preclinical and clinical studies, have strongly influenced cancer treatment guidelines in recent years, especially in immunogenic tumours. Beyond immune-based antibodies, the development of basic cancer research is focused on DNA vaccination and therapies. Significant progress has also been made in the development of plasmid DNA. The most advanced plasmid DNA and electroporation immune therapy is interleukin-12 (IL-12) immune therapy, which is already on the priority list in the US to become an orphan drug. Plasmid DNA alone cannot cross the cell membrane, so a physically mediated transfer system, electroporation, is used to transfer the plasmid to the target cells. Electroporation is currently used for electrochemotherapy (ECT) purposes (the combination of cytotoxic drugs, such as bleomycin or cisplatin, with electroporation). The application of electrical pulses increases the permeability of the cell membrane, which allows increased uptake of the drug. Determination of bleomycin concentration in blood serum or plasma and target tumour tissue in a human clinical study suggested the possibility of a decrease in bleomycin dose in elderly patients.

Electroporation can also be used for gene electrotransfer (GET) with IL-12 is one of the most advanced immune gene therapies. In preclinical and clinical studies in dogs with spontaneous tumours, it has already proven to be safe and effective. In preclinical studies in mice, the induction of long-term antitumor immunity, one of the major effects of GET with IL-12, has been demonstrated. The antitumor effect of GET IL-12 is multifaceted and includes antiangiogenic effect, activation of cytotoxic T lymphocyte activity and activation of M1 macrophages, with systemic cytokine concentration lower than recombinant cytokines or adenoviral delivery, meaning safer treatment. An important advantage of this type of treatment is the low immunogenicity of the plasmids compared to the viral vectors, which allows repeated DNA application. A clinical study treating malignant melanoma metastasis in humans has shown that intratumoural GET with IL-12 may produce a systemic "abscopal" effect on distant, untreated tumours.

The combination of ECT and GET with IL-12 is already used to treat different tumours in dogs, but many questions remain regarding bleomycin dosing, the site of administration of the plasmid, and the reasons for the individually different response to therapy.

The main objective of the proposed project is to optimize the components of combined therapy in order to improve treatment efficacy and reduce side effects. For this purpose, we will prepare a protocol for implementation of a clinical study, including a risk assessment in dogs with spontaneous tumours, in which we expect to determine the pharmacokinetic profile of bleomycin in dogs of different ages and body weights, and to determine a suitable time window for electroporation after cytostatic administration. We also expect to demonstrate that GET with intratumoral administration of IL-12 is equally or even more successful compared to peritumoral administration. By determining the expression of selected tumor-infiltrating lymphocytes (TLIs) (CD8 +, Treg) and programmed death receptors and ligands (PD-1/PDL-1) in tissue specimens prior to treatment, we will be able to determine the frequency and number of treatments in correlation with clinical data. Better response to treatment is expected in animals where there are fewer regulatory T lymphocytes and PD-1 positive cells in the tumour microenvironment, and in animals where IL-12 GET treatment will result in a decrease in circulating regulatory T lymphocytes and CD8 + lymphocytes. Prior to treatment, we will also analyze the composition of the intestinal microbiota and, in correlation with the success of the therapy and other biomarkers, we will prepare recommendations for regulating the intestinal microbiota.



© 2019 - Institute of Oncology Ljubljana
color contrast
text size
highlighting content
zoom in