Abstract
Although most malignant tumors are epithelia-derived carcinomas, methods for specific and effective delivery of antitumor agents to carcinomas have not been developed. Recent reports indicate that epithelia overexpress claudin-3 and -4, which are integral membrane proteins of epithelial tight junctions. This suggests that claudins can be targeted for tumor therapy, but there is not currently a method for delivering drugs to claudin-expressing cells. In the present study, we evaluated whether a potent claudin-4-binding C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) would allow targeting to claudin-4-expressing cells. We fused C-CPE to the protein synthesis inhibitory factor (PSIF), which lacks the cell binding domain of Pseudomonas exotoxin. This fusion protein, C-CPE-PSIF, was cytotoxic to MCF-7 human breast cancer cells, which express endogenous claudin-4, but it was not toxic to mouse fibroblast L cells, which lack endogenous claudin-4. The cytotoxicity of C-CPE-PSIF was attenuated by pretreating the MCF-7 cells with C-CPE but not bovine serum albumin. Also, deletion of the claudin-4-binding region of C-CPE reduced the cytotoxicity of C-CPE-PSIF. Finally, we found that C-CPE-PSIF is toxic to L cells expressing claudin-4 but not to normal L cells or cells expressing claudin-1, -2, or -5. These results indicate that use of the C-CPE peptide may provide a novel way to target drugs to claudin-expressing cells.
Footnotes
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This work was partly supported by a grand-in-aid of the Ministry of Education, Sports and Science in Japan.
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C.E. and M.K. contributed equally to this work.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.093351.
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ABBREVIATIONS: TJ, tight junction; CPE, C. perfringens enterotoxin; C-CPE, C-terminal fragment of C. perfringens enterotoxin; PSIF, protein synthesis inhibitory factor derived from Pseudomonas exotoxin; PE, Pseudomonas exotoxin; C-CPE-PSIF, C-terminal fragment of C. perfringens enterotoxin fused to a protein synthesis inhibitory factor; BSA, bovine serum albumin; PCR, polymerase chain reaction; PBS, phosphate-buffered saline; PAGE, polyacrylamide gel electrophoresis; LDH, l-lactate dehydrogenase.
- Received July 26, 2005.
- Accepted September 2, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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