多剤耐性遺伝子(MDR1)過剰発現肝細胞癌に対するelectrochemotherapyの有用性に関する基礎的検討

Abstract

The aim of this study was to investigate the role of electroporation in the treatment of carcinoma expressing multidrug resistance gene 1 (MDR1). The cells stably expressing MDR1 gene (BNL/MDR1-Bulk) and the clone expressing the MDR1 gene at the highest level (BNL/MDR1-Clone) were established by transducing human MDR1 gene into the mouse hepatocellular carcinoma (HCC) cell line, BNLIME.7R.1. The expressions of P-glycoprotein on the cell surface of the established HCC cells, BNL/MDR1-Bulk and BNL/MDR1-Clone, were determined by fluorescence-activated cell sorter (FACS) with the monoclonal antibody MRK16, specific against human P-glycoprotein. BNL/MDR1-Bulk expressed P-glycoprotein on the cell surface at various levels, and BNL/MDR1-Clone expressed it at the highest level. In vitro, BNL/MDR1-Bulk and BNL/MDR1-Clone exhibited approximately 8-fold and 10-fold higher resistance against adriamycin, respectively, 4-fold and 10-fold higher resistance against vinblastin, respectively, and 2-fold and 5-fold higher resistance against mitomycin C, respectively. When these cells were exposed to adriamycin with electroporation in vitro, the chemosensitivities against adriamnycin were increased, reaching the level of the parental cells (BNL/Wild). In the mouse models of subcutaneous tumors produced by inoculation of these cells, electroporation alone or injection of adriamycin at 1/10 of the 50% lethal dosage could not inhibit the growth of the tumor. However, electrochemotherapy consisting of adriamycin injection with electroporation did inhibit tumor growth not only in mice inoculated with the parental HCC cells or BNL/Wild cells, but also in P-glycoprotein presenting mice inoculated with BNL/MDR1-Bulk or BNL/MDR1-Clone. These results indicated that electrochemotherapy has the potential to overcome the tumor resistance related to MDR function in hepatoma cells.