The effect of intraperitoneal administration of clostridium perfringens enterotoxin on chemotherapy-resistant CD44+ human ovarian cancer stem cells in mice.

Abstract

e13077 Background: Emerging evidence has suggested that the capability to sustain tumor formation, growth and chemotherapy-resistance in ovarian, as well as other human malignancies, exclusively resides in a small proportion of tumor cells termed cancer stem cells (CSCs). During the characterization of CD44+ ovarian CSCs, we found a high expression of the genes encoding for claudin-4. Because this tight junction protein is the natural high affinity receptor for Clostridium perfringens enterotoxin (CPE), we have extensively investigated the sensitivity of ovarian CSC to CPE treatment in vitro and in vivo. Methods: Real-time polymerase-chain-reaction and flow cytometry were used to evaluate claudin-3/-4 expression in ovarian CSCs. Small-interfering-RNA-knockdown experiments, and MTS-assays were used to evaluate CPE-induced cytotoxicity against ovarian CSC lines in vitro. C.B-17/SCID mice harboring ovarian CSC xenografts were used to evaluate CPE therapeutic activity in vivo. Results: CD44+ ovarian CSCs expressed claudin-4 gene at significantly higher levels than matched autologous CD44- ovarian cancer cells and, regardless of their higher resistance to chemotherapeutic agents, died within 1 hour after exposure to 1.0μg/ml of CPE in vitro. Conversely, small-interfering-RNA–mediated knockdown of claudin-3/-4 expression in CD44+ CSCs significantly protected CSCs from CPE-induced-cytotoxicity. Importantly, multiple intraperitoneal administrations of sublethal doses of CPE in mice harboring xenografts of chemotherapy resistant CD44+ ovarian CSCs had a significant inhibitory effect on tumor progression leading to the cure and/or long-term survival of all treated animals. Conclusions: CPE may represent an unconventional, potentially highly effective strategy to eradicate chemotherapy-resistant CSCs.