Risk prediction of gastric cancer by analysis of aberrant DNA methylation in non-neoplastic gastric epithelium.
BACKGROUND
Aberrant DNA methylation is one of the major events in carcinogenesis. Promoter DNA methylation is also present in various non-neoplastic tissues including gastric epithelium as age-related phenomenon, suggesting that it occurs early in the process of tumorigenesis.


OBJECTIVE
We aimed to clarify the relationship of aberrant DNA methylation in non-neoplastic gastric epithelia with the risk of gastric cancer, Helicobactor pylori infection, and the degree of H. pylori-induced gastritis.


METHODS
89 patients enrolled in this study. The status of aberrant DNA methylation was compared in two groups of patients: 43 cases with gastric cancer (mean age 65.9 years [29-91], F:M = 0.30, intestinal type [n = 25], diffuse type [n = 18]) and 46 age- and sex-matched patients without gastric cancer (peptic ulcer diseases [n = 11], gastritis [n = 35]) as a control group. Genomic DNA was extracted directly from non-neoplastic epithelia of antral biopsies obtained by endoscopy. The promoter methylation status of the p14 and p21 genes was determined by methylation-specific-polymerase chain reaction (MSP). The promoter methylation status of the p16 gene was quantified by digital densitographic analysis following MSP. The degree of gastritis in the antrum was assessed according to the updated Sydney system. The PG I/II ratio was calculated based on the data of serum PG I and PG II levels measured by radioimmunoassay.


RESULTS
In all 89 subjects, CpG island methylation was found in 25.8% for p14, 52.8% for p16, 1.1% for p21. Among non-cancer patients, the methylation frequency of the p14 gene was significantly higher in H. pylori-positive than in H. pylori-negative patients (38.5 vs. 10.0%, p = 0.03). The mean (+/- SD) methylation levels of the p16 gene in non-neoplastic gastric epithelium was significantly higher in gastric cancer cases both in all patients and in H. pylori-positive patients (0.45 +/- 0.31 vs. 0.20 +/- 0.17; p = 0.019, 0.45 +/- 0.31 vs. 0.20 +/- 0.17; p = 0.016, respectively). The methylation level of the p16 gene was also associated with the presence of intestinal-type gastric cancer (p = 0.017). The methylation level of the p16 gene was significantly higher in patients with intestinal metaplasia (IM) than those without (p = 0.04). Furthermore, the methylation level of the p16 gene was correlated with lower PG l/ll ratio (p = 0.04). The methylation of the p21gene was found in only 1 patient with gastric cancer.


CONCLUSIONS
Our data suggest that promoter of the p14 gene may be one of the specific regions whose methylation is closely associated with H. pylori infection. Methylation levels of the p16 gene seem to be accumulated in the progression of gastric mucosal atrophy and IM, and thus may be associated with the presence of gastric cancer especially for intestinal-type histopathology.
Tahara
Tomomitsu
T
Department of Gastroenterology, Fujita Health University School of Medicine, Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, Japan. tomomiccyu@yahoo.co.jp
Arisawa
Tomiyasu
T
Shibata
Tomoyuki
T
Wang
Fang Yu
FY
Nakamura
Masakatsu
M
Sakata
Mikijyu
M
Nagasaka
Mitsuo
M
Takagi
Tamaki
T
Kamiya
Yoshio
Y
Fujita
Hiroshi
H
Nakamura
Masahiko
M
Hasegawa
Shin
S
Iwata
Masami
M
Takahama
Kazuya
K
Watanabe
Makoto
M
Hirata
Ichiro
I
Nakano
Hiroshi
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018899:CpG Islands / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D019175:DNA Methylation; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D005756:Gastritis / Q000235:genetics / Q000382:microbiology / Q000473:pathology; D016147:Genes, Tumor Suppressor; D019942:Genes, p16; D020022:Genetic Predisposition to Disease; D016481:Helicobacter Infections / Q000150:complications; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000235:genetics* / Q000382:microbiology; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics
D050759:Cyclin-Dependent Kinase Inhibitor p21; D025803:Tumor Suppressor Protein p14ARF