Background Bacterial toxins have evolved to an effective therapeutic option
for cancer therapy. The Clostridium perfringens enterotoxin (CPE) is a pore-
forming toxin with selective cytotoxicity. The transmembrane tight junction
proteins claudin-3 and -4 are known high affinity CPE receptors. Their
expression is highly upregulated in human cancers, including breast, ovarian
and colon carcinoma. CPE binding to claudins triggers membrane pore complex
formation, which leads to rapid cell death. Previous studies demonstrated the
anti-tumoral effect of treatment with recombinant CPE-protein. Our approach
aimed at evaluation of a selective and targeted cancer gene therapy of
claudin-3- and/or claudin-4- expressing colon carcinoma in vitro and in vivo
by using translation optimized CPE expressing vector. Methods In this study
the recombinant CPE and a translation optimized CPE expressing vector (optCPE)
was used for targeted gene therapy of claudin-3 and/or -4 overexpressing colon
cancer cell lines. All experiments were performed in the human SW480, SW620,
HCT116, CaCo-2 and HT-29 colon cancer and the isogenic Sk-Mel5 and Sk-Mel5
Cldn-3-YFP melanoma cell lines. Claudin expression analysis was done at
protein and mRNA level, which was confirmed by immunohistochemistry. The CPE
induced cytotoxicity was analyzed by the MTT cytotoxicity assay. In addition
patient derived colon carcinoma xenografts (PDX) were characterized and used
for the intratumoral in vivo gene transfer of the optCPE expressing vector in
PDX bearing nude mice. Results Claudin-3 and -4 overexpressing colon carcinoma
lines showed high sensitivity towards both recCPE application and optCPE gene
transfer. The positive correlation between CPE cytotoxicity and level of
claudin expression was demonstrated. Transfection of optCPE led to targeted,
rapid cytotoxic effects such as membrane disruption and necrosis in claudin
overexpressing cells. The intratumoral optCPE in vivo gene transfer led to
tumor growth inhibition in colon carcinoma PDX bearing mice in association
with massive necrosis due to the intratumoral optCPE expression. Conclusions
This novel approach demonstrates that optCPE gene transfer represents a
promising and efficient therapeutic option for a targeted suicide gene therapy
of claudin-3 and/or claudin-4 overexpressing colon carcinomas, leading to
rapid and effective tumor cell killing in vitro and in vivo