Claudin‐4 binder C‐CPE 194 enhances effects of anticancer agents on pancreatic cancer cell lines via a MAPK pathway

The C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) modulates the tight junction protein claudin and disrupts the tight junctional barrier. It also can enhance the effectiveness of anticancer agents. However, the detailed mechanisms of the effects of C-CPE remain unclear in both normal and cancerous cells. The C-CPE mutant called C-CPE 194 binds only to claudin-4, but the C-CPE 194 mutant called C-CPE m19 binds not only to claudin-4 but also to claudin-1. In the present study, to investigate the mechanisms of the effects of C-CPE on claudin expression, the tight junctional functions and the cytotoxicity of anticancer agents, human pancreatic cancer cells, and normal human pancreatic duct epithelial cells (HPDEs) were treated with C-CPE 194 and C-CPE m19. In well-differentiated cells of the pancreatic cancer cell line HPAC, C-CPE 194 and C-CPE m19 disrupted both the barrier and fence functions without changes in expression of claudin-1 and -4, together with an increase of MAPK phosphorylation. C-CPE 194, but not C-CPE m19, enhanced the cytotoxicity of the anticancer agents gemcitabine and S-1. In poorly differentiated pancreatic cancer cell line PANC-1, C-CPE 194, but not C-CPE m19, decreased claudin-4 expression and enhanced MAPK activity and the cytotoxicity of the anticancer agents. In normal HPDEs, C-CPE 194 and C-CPE m19 decreased claudin-4 expression and enhanced the MAPK activity, whereas they did not affect the cytotoxicity of the anticancer agents. Our findings suggest that the claudin-4 binder C-CPE 194 enhances effects of anticancer agents on pancreatic cancer cell lines via a MAPK pathway.