Transcriptional silencing of Dickkopf gene family by CpG island hypermethylation in human gastrointestinal cancer.
OBJECTIVE
To clarify alterations of Dickkopfs (Dkks) and Kremen2 (Krm2) in gastrointestinal cancer.


METHODS
We investigated the expression profiles and epigenetic alterations of Dkks and Krm2 genes in gastrointestinal cancer using RT-PCR, tissue microarray analysis, and methylation specific PCR (MSP). Cancer cells were treated with the demethylating agent and/or histone deacetylase inhibitor. WST-8 assays and in vitro invasion assays after treatment with specific siRNA for those genes were performed.


RESULTS
Dkks and Krm2 expression levels were reduced in a certain subset of the gastrointestinal cancer cell lines and cancer tissues. This was correlated with promoter hypermethylation. There were significant correlations between Dkks over-expression levels and beta-catenin over-expression in colorectal cancer. In colorectal cancers with beta-catenin over-expression, Dkk-1 expression levels were significantly lower in those with lymph node metastases than in those without. Down-regulation of Dkks expression by siRNA resulted in a significant increase in cancer cell growth and invasiveness in vitro.


CONCLUSIONS
Down-regulation of the Dkks associated to promoter hypermethylation appears to be frequently involved in gastrointestinal tumorigenesis.
Maehata
Tadateru
T
Department of Gastroenterology and Hepatology, St. Marianna University School of Medicine, Kanagawa, Japan
Taniguchi
Hiroaki
H
Yamamoto
Hiroyuki
H
Nosho
Katsuhiko
K
Adachi
Yasushi
Y
Miyamoto
Nobuki
N
Miyamoto
Chie
C
Akutsu
Noriyuki
N
Yamaoka
Satoshi
S
Itoh
Fumio
F
D048868:Adaptor Proteins, Signal Transducing; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D018925:Chemokines; D018899:CpG Islands; D019175:DNA Methylation; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics; D009361:Neoplasm Invasiveness; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011956:Receptors, Cell Surface; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D046888:Tissue Array Analysis; D014158:Transcription, Genetic; D014162:Transfection; D051176:beta Catenin / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; C495270:CTNNB1 protein, human; D018925:Chemokines; C501126:DKK1 protein, human; C498622:DKK2 protein, human; C498624:DKK3 protein, human; C442333:DKK4 protein, human; D036341:Intercellular Signaling Peptides and Proteins; C486076:KREMEN2 protein, human; D008565:Membrane Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D051176:beta Catenin