Claudin-4:: A new target for pancreatic cancer treatment using Clostridium perfringens enterotoxin

Background & Aims. Recently, several members of the claudin family have been identified as integral constituents of tight junctions. Using expression profiling, we previously found claudin-4 to be overexpressed in pancreatic cancer. Because claudin-4 has been described as a receptor for the cytotoxic Clostridium perfringens enterotoxin (CPE), we investigated the effect of CPE on pancreatic cancer cells. Methods: Expression of claudin-4 was analyzed by Northern blots. In vitro toxicity of CPE was determined by trypan blue exclusion and the Rb-86-release assay. The in vivo effect of CPE was studied in claudin-4-expressing nude mouse xenografts of the Panc-1 cell line. Results: Expression analyses showed that claudin-4 was overexpressed in most pancreatic cancer tissues and cell lines and several other gastrointestinal tumors. CPE led to an acute dose-dependent cytotoxic effect, restricted to claudin-4-expressing cells and dependent on claudin-4 expression levels. Furthermore, transforming growth factor beta was identified as a negative modulator of both claudin-4 expression and susceptibility to CPE. In vivo, intratumoral injections of CPE in Panc-1. xenografts led to large areas of tumor cell necrosis and significant reduction of tumor growth. Conclusions: Our findings suggest that targeting claudin-4-expressing tumors with CPE represents a promising new treatment modality for pancreatic cancer and other solid tumors.