Factors affecting combined electrochemotherapy with immunogene therapy of cancer

Principal Investigator at the Institute of Oncology Ljubljana: prof. dr. Gregor Serša

The principle barrier for non-permeant anti-tumor agents that have an intracellular site of action is the cell membrane and cytotoxicity is dependent upon membrane permeability. Considerable efforts to develop effective delivery approaches has shown that pulsed electric fields can be utilized to permeabilize cell membranes and allow molecules to gain greater access to the cytosol (electroporation. Electroporation can be utilized for either chemotherapeutics (electrochemotherapy, ECT) or gene based therapies (gene electrotransfer, GET), as demonstrated in both, preclinical and clinical studies. ECT is now routinely used in many European countries, and has gained approval by the National Institute for Health and Care Excellence (NICE) of the UK. ECT has shown remarkable results achieving close to 70% complete response rates of treated tumor lesions. The limitation of this ablative technique is that responses are local, without any effect on distant, nontreated lesions. Delivery of plasmids encoding cytokines using GET has also achieved significant results in both veterinary and clinical trials in US. Utilizing this GET approach responses have been seen in some patients not only in the treated lesions but also untreated lesions. The results obtained in preclinical, veterinary and human studies have clearly demonstrated the potential for both ECT and GET approaches. It is clear that both approaches can be safely administered and can effectively deliver the anti-tumor agent. Independently, both have some shortcomings. Recently there have been studies conducted in veterinary patients that have demonstrated a potential synergy between ECT and GET. ECT can effectively reduce tumor burden and induce immunogenic cell death which can be used as a priming mechanism for subsequent immune enhancement (in situ vaccination). The concomitant administration of GET delivery of an immune stimulating agent can elevate the localized response to a systemic response (abscopal effect). We hypothesize that if ECT is combined with GET delivery of immune stimulating molecules in the correct sequence and location, then a systemic and durable therapeutic response will be achieved. Therefore, it is critical to characterize the tumor microenvironment following ECT to characterize the potential for immune stimulation. This will be critical for establishing the sequence and timing of the combined ECT and EGT treatments.

For this purpose, research groups of prof. Serša and prof. Heller have a mutual goal to develop this combined therapy, and translate it into the clinics through optimizing it on preclinical level. Specific aims of the projects are:

• Explore biological characteristics and molecular markers as predictive factors for better effectiveness of ECT alone or in combination withimmunogene therapy.
• Test the most effective and the most rational way of electric pulse delivery for chemotherapeutic drug and plasmid DNA for immunogene therapy.
• Conceptualize this approach in mutual publications.
• Present the concept and the results at the international conferences.
• Convey the knowledge to postgraduate students in MSc and PhD programmes.