Silencing of claudin-11 is associated with increased invasiveness of gastric cancer cells.
BACKGROUND
Claudins are membrane proteins that play critical roles in tight junction (TJ) formation and function. Members of the claudin gene family have been demonstrated to be aberrantly regulated, and to participate in the pathogenesis of various human cancers. In the present study, we report that claudin-11 (CLDN11) is silenced in gastric cancer via hypermethylation of its promoter region.


RESULTS
Levels of CLDN11 methylation and mRNA expression were measured in primary gastric cancer tissues, noncancerous gastric mucosae, and cell lines of gastric origin using quantitative methylation-specific PCR (qMSP) and quantitative reverse transcriptase-PCR (qRT-PCR), respectively. Analyses of paired gastric cancers and adjacent normal gastric tissues revealed hypermethylation of the CLDN11 promoter region in gastric cancers, and this hypermethylation was significantly correlated with downregulation of CLDN11 expression vs. normal tissues. The CLDN11 promoter region was also hypermethylated in all gastric cancer cell lines tested relative to immortalized normal gastric epithelial cells. Moreover, CLDN11 mRNA expression was inversely correlated with its methylation level. Treatment of CLDN11-nonexpressing gastric cancer cells with 5-aza-2'-deoxycytidine restored CLDN11 expression. Moreover, siRNA-mediated knockdown of CLDN11 expression in normal gastric epithelial cells increased their motility and invasiveness.


CONCLUSIONS
These data suggest that hypermethylation of CLDN11, leading to downregulated expression, contributes to gastric carcinogenesis by increasing cellular motility and invasiveness. A further understanding of the mechanisms underlying the role of claudin proteins in gastric carcinogenesis will likely help in the identification of novel approaches for diagnosis and therapy of gastric cancer.
Agarwal
Rachana
R
Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America. ragarwa9@jhmi.edu
Mori
Yuriko
Y
Cheng
Yulan
Y
Jin
Zhe
Z
Olaru
Alexandru V
AV
Hamilton
James P
JP
David
Stefan
S
Selaru
Florin M
FM
Yang
Jian
J
Abraham
John M
JM
Montgomery
Elizabeth
E
Morin
Patrice J
PJ
Meltzer
Stephen J
SJ
D001374:Azacitidine / Q000031:analogs & derivatives / Q000378:metabolism; D014408:Biomarkers, Tumor; D045744:Cell Line, Tumor; D002465:Cell Movement; D057167:Claudins; D019175:DNA Methylation; D000077209:Decitabine; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D009361:Neoplasm Invasiveness; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000378:metabolism*
D014408:Biomarkers, Tumor; C120453:CLDN11 protein, human; D057167:Claudins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D000077209:Decitabine; D001374:Azacitidine