Purpose: To evaluate the expression levels of claudin-3 and claudin-4, the low- and high-affinity receptors, respectively, for the cytotoxic Clostridium perfringens enterotoxin (CPE) in uterine carcinosarcomas and explore the potential for targeting these receptors in the treatment of this aggressive uterine tumor.
Experimental design: We analyzed claudin-3 and claudin-4 receptor expression at mRNA and protein levels in flash frozen and formalin-fixed, paraffin-embedded carcinosarcoma specimens. Recombinant CPE was used as a novel therapy against chemotherapy-resistant carcinosarcoma cell lines in vitro. The therapeutic effect of sublethal doses of CPE was studied in severe combined immunodeficient mouse xenografts harboring large s.c. carcinosarcomas.
Results: All flash-frozen carcinosarcoma biopsies (12 of 12) and short-term carcinosarcoma cell lines evaluated overexpressed claudin-3 and claudin-4 by quantitative reverse transcription-PCR. Membranous immunoreactivity for claudin-4 protein expression was documented in 80% (20 of 25) of primary tumors and 100% (6 of 6) of the metastatic carcinosarcomas, whereas negligible staining was found in normal endometrial cells. Regardless of their resistance to chemotherapeutic agents, all short-term carcinosarcoma cell lines tested died within 1 h of exposure to 3.3 microg/mL of CPE in vitro. Intratumoral injections of well-tolerated doses of CPE in large s.c. carcinosarcoma xenografts led to large areas of tumor cell necrosis and tumor disappearance in all treated animals.
Conclusions: Claudin-3 and claudin-4 receptors are highly overexpressed in carcinosarcoma. These proteins may offer promising targets for the use of CPE as a novel type-specific therapy against this biologically aggressive variant of endometrial cancer.