Targeted cancer gene therapy by clostridium perfringens enterotoxin (CPE) gene transfer

The bacterial Clostridium perfringens enterotoxin (CPE) is produced by the Clostridium strain type A. The transmembrane tight junction proteins claudin 3 and 4 are the specific receptors for CPE, which are overexpressed in human epithelial tumors such as colon, breast, pancreatic and ovarian cancer. CPE binding to the claudins forms membrane pore complexes resulting in rapid cell death. The tumor-specific claudin 3 and 4 overexpression can be used for targeted cell killing by CPE. This study aimed at tumor cell killing by CPE gene transfer. We generated expression vectors carrying the CPE cDNA, which were tested for in vitro gene therapy of claudin 3 and 4 overexpressing human cancer cell lines HCT116, MCF-7 and Panc-1. CPE expression analysis by realtime PCR at mRNA and by Western-blotting at protein level revealed efficient in vitro CPE expression leading to cytotoxic activity after transfection. The highest cytotoxic effect of up to 70% cell killing was observed 48 h after transfection and was dependent on the claudin 4 expression level. Therefore, MCF-7 cells with the highest claudin 4 expression showed the highest sensitivity to CPE. The antitumoral effect of CPE gene transfer in vivo was tested in MCF-7 tumor-bearing nude mice. The in vivo electroporation mediated gene transfer of the CPE-expressing vector led to reduced tumor growth in tumor-bearing mice compared to the untreated control group. These results provide first evidence, that CPE gene transfer can be used for a novel suicide gene therapy of claudin 4 and 3 overexpressing tumors, leading to a rapid and efficient cell killing in vitro and in vivo.