C terminus of Clostridium perfringens enterotoxin downregulates CLDN4 and sensitizes ovarian cancer cells to Taxol and Carboplatin.
OBJECTIVE
We have previously shown that CLDN4 (encoding claudin-4), a cell tight junction (TJ) protein, is highly expressed in human epithelial ovarian carcinomas (EOC) but undetectable in normal ovaries. CLDN4 has been identified as a specific receptor for C terminus of Clostridium perfringens enterotoxin (C-CPE), a nontoxic molecule that may disrupt TJ barrier function and enhance cellular absorption. The purpose of this study was to determine the potential clinical applications of C-CPE and its effects on CLDN4 expression in EOC.


METHODS
Using a 3-dimensional culture model and monolayer culture of EOC cells, we examined the effects of C-CPE on CLDN4 expression by quantitative real-time PCR, immunofluorescence, and Western blot. The synergistic effect of C-CPE to clinically relevant chemotherapies (Taxol and Carboplatin) was observed in EOC culture and xenograft mice. Furthermore, we determined through oligonucleotide microarray analysis that the transcript profile alterations dysregulated as a consequence of C-CPE treatment.


RESULTS
C-CPE treatment decreased protein expression and relocated CLDN4 from cell-cell contact regions to the cytoplasm. Particularly, C-CPE sensitized EOC cells to chemotherapeutic administration at low dosages and significantly inhibited tumor growth in a nontoxic manner. Furthermore, we provided genome-wide molecular evidence that C-CPE treatment is involved in the stimulation of the ubiquitin-proteasome pathway and the inhibition of cell metabolism in EOC cells.


CONCLUSIONS
The addition of C-CPE can enhance the effectiveness of Taxol or Carboplatin and significantly inhibited EOC cell growth in a CLDN4-dependent manner, suggesting that C-CPE may have promising therapeutic potential for EOC.
Division of Gynecologic Oncology, Department of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA. zhijian_gao@yahoo.com
Zhijian
Z
Gao
Xiaoyin
X
Xu
Bruce
B
McClane
Qing
Q
Zeng
Babak
B
Litkouhi
William R
WR
Welch
Ross S
RS
Berkowitz
Samuel C
SC
Mok
Elizabeth I O
EI
Garner
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D015153:Blotting, Western; D016190:Carboplatin / Q000494:pharmacology / Q000627:therapeutic use*; D000077216:Carcinoma, Ovarian Epithelial; D002478:Cells, Cultured; D062506:Claudin-4; D003016:Clostridium perfringens / Q000378:metabolism; D004768:Enterotoxins / Q000627:therapeutic use*; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D020287:In Situ Nick-End Labeling; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009375:Neoplasms, Glandular and Epithelial / Q000188:drug therapy* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology / Q000627:therapeutic use*; D016133:Polymerase Chain Reaction; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D019108:Tight Junctions; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; C568157:CLDN4 protein, human; D062506:Claudin-4; C568158:Cldn4 protein, mouse; D004768:Enterotoxins; D008565:Membrane Proteins; D012333:RNA, Messenger; C035598:enterotoxin, Clostridium; D016190:Carboplatin; D043743:Ubiquitin-Protein Ligase Complexes; D046988:Proteasome Endopeptidase Complex; D017239:Paclitaxel