title: Claudin-4 overexpression in epithelial ovarian cancer is associated with hypomethylation and is a potential target for modulation of tight junction barrier function using a C-terminal fragment of Clostridium perfringens enterotoxin.
abstract: BACKGROUND
  Claudin-4, a tight junction (TJ) protein and receptor for the C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE), is overexpressed in epithelial ovarian cancer (EOC). Previous research suggests DNA methylation is a mechanism for claudin-4 overexpression in cancer and that C-CPE acts as an absorption-enhancing agent in claudin-4-expressing cells. We sought to correlate claudin-4 overexpression in EOC with clinical outcomes and TJ barrier function, investigate DNA methylation as a mechanism for overexpression, and evaluate the effect of C-CPE on the TJ.
  
  
  METHODS
  Claudin-4 expression in EOC was quantified and correlated with clinical outcomes. Claudin-4 methylation status was determined, and claudin-4-negative cell lines were treated with a demethylating agent. Electric cell-substrate impedance sensing was used to calculate junctional (paracellular) resistance (Rb) in EOC cells after claudin-4 silencing and after C-CPE treatment.
  
  
  RESULTS
  Claudin-4 overexpression in EOC does not correlate with survival or other clinical endpoints and is associated with hypomethylation. Claudin-4 overexpression correlates with Rb and C-CPE treatment of EOC cells significantly decreased Rb in a dose- and claudin-4-dependent noncytotoxic manner.
  
  
  CONCLUSIONS
  C-CPE treatment of EOC cells leads to altered TJ function. Further research is needed to determine the potential clinical applications of C-CPE in EOC drug delivery strategies.
authors: Department of Obstetrics, Gynecology and Reproductive Biology, Division of Gynecologic Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. blitkouhi@partners.org
authors: Babak
authors: B
authors: Litkouhi
authors: Joseph
authors: J
authors: Kwong
authors: Chun-Min
authors: CM
authors: Lo
authors: James G
authors: JG
authors: Smedley
authors: Bruce A
authors: BA
authors: McClane
authors: Margarita
authors: M
authors: Aponte
authors: Zhijian
authors: Z
authors: Gao
authors: Jennifer L
authors: JL
authors: Sarno
authors: Jennifer
authors: J
authors: Hinners
authors: William R
authors: WR
authors: Welch
authors: Ross S
authors: RS
authors: Berkowitz
authors: Samuel C
authors: SC
authors: Mok
authors: Elizabeth I O
authors: EI
authors: Garner
mesh_terms: D045744:Cell Line, Tumor; D062506:Claudin-4; D003016:Clostridium perfringens / Q000502:physiology*; D019175:DNA Methylation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D016503:Drug Delivery Systems / Q000379:methods; D004768:Enterotoxins / Q000008:administration & dosage* / Q000633:toxicity; D005260:Female; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D009375:Neoplasms, Glandular and Epithelial / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000633:toxicity; D019108:Tight Junctions / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*
chemical_list: C568157:CLDN4 protein, human; D062506:Claudin-4; D004768:Enterotoxins; D008565:Membrane Proteins; D010446:Peptide Fragments; C035598:enterotoxin, Clostridium