Helicobacter pylori causes epigenetic dysregulation of FOXD3 to promote gastric carcinogenesis.
OBJECTIVE
Deregulation of forkhead box (Fox) proteins, an evolutionarily conserved family of transcriptional regulators, leads to tumorigenesis. Little is known about their regulation or functions in the pathogenesis of gastric cancer. Promoter hypermethylation occurs during Helicobacter pylori-induced gastritis. We investigated whether the deregulated genes contribute to gastric tumorigenesis.


METHODS
We used integrative genome-wide scans to identify concomitant hypermethylated genes in mice infected with H pylori and human gastric cancer samples. We also analyzed epigenetic gene silencing in gastric tissues from patients with H pylori infection and gastritis, intestinal metaplasia, gastric tumors, or without disease (controls). Target genes were identified by chromatin immunoprecipitation microarrays and expression and luciferase reporter analyses.


RESULTS
Methylation profile analyses identified the promoter of FOXD3 as the only genomic region with increased methylation in mice and humans during progression of H pylori-associated gastric tumors. FOXD3 methylation also correlated with shorter survival times of patients with gastric cancer. Genome demethylation reactivated FOXD3 expression in gastric cancer cell lines. Transgenic overexpression of FOXD3 significantly inhibited gastric cancer cell proliferation and invasion, and reduced growth of xenograft tumors in mice, at least partially, by promoting tumor cell apoptosis. FOXD3 bound directly to the promoters of, and activated transcription of, genes encoding the cell death regulators CYFIP2 and RARB. Levels of FOXD3, CYFIP2, and RARB messenger RNAs were reduced in human gastric tumor samples, compared with control tissues.


CONCLUSIONS
FOXD3-mediated transcriptional control of tumor suppressors is deregulated by H pylori infection-induced hypermethylation; this could perturb the balance between cell death and survival. These findings identify a pathway by which epigenetic changes affect gastric tumor suppression.
Institute of Digestive Disease, The Chinese University of Hong Kong, Hong Kong SAR, China. alfredcheng@cuhk.edu.hk
Alfred S L
AS
Cheng
May S
MS
Li
Wei
W
Kang
Victoria Y
VY
Cheng
Jian-Liang
JL
Chou
Suki S
SS
Lau
Minnie Y
MY
Go
Ching C
CC
Lee
Thomas K
TK
Ling
Enders K
EK
Ng
Jun
J
Yu
Tim H
TH
Huang
Ka F
KF
To
Michael W
MW
Chan
Joseph J Y
JJ
Sung
Francis K L
FK
Chan
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D051858:Forkhead Transcription Factors / Q000235:genetics*; D005756:Gastritis / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D016481:Helicobacter Infections / Q000235:genetics*; D016480:Helicobacter pylori; D006801:Humans; D007422:Intestines / Q000473:pathology; D053208:Kaplan-Meier Estimate; D008297:Male; D008679:Metaplasia / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D011379:Prognosis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics* / Q000382:microbiology
D048868:Adaptor Proteins, Signal Transducing; C518673:CYFIP2 protein, human; C503514:FOXD3 protein, human; D051858:Forkhead Transcription Factors; C101757:Foxd3 protein, mouse; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; C082925:retinoic acid receptor beta