[The role of secreted Wnt-antagonist genes hypermethylation in early detection of colorectal tumor].
OBJECTIVE
To investigate the functions of promoter hypermethylation of secreted Wnt-antagonist genes in colorectal tumorigenesis and progression.


METHODS
Two colorectal cancer cell lines, HCT116 and SW480, were treated by 5-aza-2'-deoxycytidine (DAC) and trichostatin A (TSA) for demethylation. The promoter hypermethylation and expression of sFRP and WIF-1 genes in different stages of colorectal tumor and colorectal cancer cell lines were detected by methylation-specific PCR and reverse transcription PCR, respectively.


RESULTS
None of the normal colorectal mucosa samples showed methylated bands of any sFRP and WIF-1genes. Hypermethylation of sFRP1, 2, 4, 5 and WIF-1 was detected in 93.1% (67/72), 83.3% (60/72), 36.1% (26/72), 52.8% (38/72) and 84.7% (61/72) of adenocarcinomas, 87.9% (29/33), 81.8% (27/33), 24.2% (8/33), 57.6% (19/33) and 72.7% (24/33) of adenomas, 52.6%, 28.9%, 2.6%, 18.4%, 23.7% of the adjacent normal mucosa. Methylation was more frequently found in colorectal tumors than in normal mucosa and adjacent normal mucosa from patients with tumor (P < 0.05). No significant association between Wnt-antagonist genes hypermethylation and clinicopathological characteristics was found (P > 0.05). SFRP1, 2, 4, 5 and WIF-1 genes were methylated in HCT116 cell line. SFRP1, 2 and WIF-1 were methylated in SW480 cell line. The mRNA expression of sFRPs and WIF-1 genes was absent or significantly downregulated (P < 0.01) when they were methylated in two colorectal cancer cell lines. SFRP3 was expressed in two colorectal carcinoma cell lines. DAC/TSA combination treatment re-expressed the silenced sFRPs and WIF-1 genes mRNA expressions effectively. A single application of TSA could not re-express sFRPs and WIF-1 genes mRNA expressions. The influence of demethylation treatment on sFRP3 expression was minimal.


CONCLUSIONS
Hypermethylation of Wnt-antagonist genes is a common early event in the evolution of colorectal tumor. Methylation of sFRP1, 2, 5 and WIF-1 genes might serve as biomarkers for the early detection of colorectal tumor.
Qi
Jian
J
The Zhongnan Hospital of Wuhan University, Wuhan 430071, China.
Zhu
You-qing
YQ
Luo
Jun
J
Tao
Wen-hui
WH
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000230:Adenocarcinoma / Q000175:diagnosis / Q000235:genetics; D000236:Adenoma / Q000175:diagnosis / Q000235:genetics; D000328:Adult; D000368:Aged; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics; D019175:DNA Methylation; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006023:Glycoproteins / Q000235:genetics*; D045325:HCT116 Cells; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099274:Frizzled-Related Proteins
D048868:Adaptor Proteins, Signal Transducing; D001374:Azacitidine; D000077209:Decitabine; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D006877:Hydroxamic Acids; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D000099274:Frizzled-Related Proteins; C485569:WIF1 protein, human; C012589:trichostatin A