Feasibility and safety of electrochemotherapy (ECT) in the pancreas: a pre-clinical investigation

Background. Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease generally refractory to standard chemotherapeutic agents; therefore improvements in anticancer therapies are mandatory. A major determinant of therapeutic resistance in PDAC is the poor drug delivery to neoplastic cells, mainly due to an extensive fibrotic reaction. Electroporation can be used in vivo to increase cancer cells' local uptake of chemotherapeutics (electrochemotherapy, ECT), thus leading to an enhanced tumour response rate. In the present study, we evaluated the in vivo effects of reversible electroporation in normal pancreas in a rabbit experimental model. We also tested the effect of electroporation on pancreatic cancer cell lines in order to evaluate their increased sensitivity to chemotherapeutic agents. Materials and methods. The application in vivo of the European Standard Operating Procedure of Electrochemotherapy (ESOPE) pulse protocol (1000 V/cm, 8 pulses, 100 μs, 5 KHz) was tested on the pancreas of normal New Zealand White Rabbits and short and long-term toxicity were assessed. PANC1 and MiaPaCa2 cell lines were tested for in vitro electrochemotherapy experiments with and without electroporation. Levels of cell permeabilization were determined by flow cytometry, whereas cell viability and drug (cisplatin and bleomycin) sensitivity of pulsed cells were measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Results. In healthy rabbits, neither systemic nor local toxic effects due to the electroporation procedure were observed, demonstrating the safety of the optimized electric parameters in the treatment of the pancreas in vivo. In parallel, we established an optimized protocol for ECT in vitro that determined an enhanced anti-cancer effect of bleomycin and cisplatin with respect to treatment without electroporation. Conclusions. Our data suggest that electroporation is a safe procedure in the treatment of PDAC because it does not affect normal pancreatic parenchyma, but has a potentiating effect on cytotoxicity of bleomycin in pancreatic tumour cell lines. Therefore, ECT could be considered as a valid alternative for the local control of non-resectable pancreatic cancer.