The presence of aberrant DNA methylation in noncancerous esophageal mucosae in association with smoking history: a target for risk diagnosis and prevention of esophageal cancers.
BACKGROUND
Esophageal squamous cell carcinomas (ESCCs) tend to have multiple primary lesions, and it is believed that they arise from background mucosae with accumulation of genetic/epigenetic alterations. In this study, the objective was to elucidate the effects of smoking and drinking on the accumulation of epigenetic alterations in background mucosae.


METHODS
Genes that are silenced in human ESCCs were searched for by treating 3 ESCC cell lines with the demethylating agent, 5-aza-2'-deoxycytidine and performing oligonucleotide microarrays. Methylation levels were analyzed by quantitative methylation-specific polymerase chain reaction analysis of 60 ESCCs and their corresponding background mucosae.


RESULTS
Forty-seven genes were identified as methylation-silenced in at least 1 of the 3 ESCC cell lines, and 14 of those genes (claudin 6 [CLDN6]; G protein-coupled receptor 158 [GPR158]; homeobox A9 [HOXA9]; metallothionein 1M [MT1M]; neurofilament, heavy polypeptide 200 kDa [NEFH]; plakophilin 1 [PKP1]; protein phosphatase 1, regulatory [inhibitor] subunit 14A [PPP1R14A]; pyrin domain and caspase recruitment domain containing [PYCARD]; R-spondin family, member 4 [RSPO4]; testis-specific protein, Y-encoded-like 5 [TSPYL5]; ubiquitin carboxyl-terminal esterase L1 [UCHL1]; zinc-finger protein 42 homolog [ZFP42]; zinc-finger protein interacting with K protein 1 homolog [ZIK1]; and zinc-finger and SCAN domain containing 18 [ZSCAN18]) were used as markers. In the background mucosae, methylation levels of 5 genes (HOXA9, MT1M, NEFH, RSPO4, and UCHL1) had significant correlations with smoking duration (rho=.268; P=.044; rho=.405; P=.002; rho=.285; P=.032; rho=.300; P=.024; and rho=.437; P=.001, respectively). In contrast, an inverse correlation between PYCARD methylation levels and alcohol intake was observed (rho=-.334, P=.025) among individuals with the inactive aldehyde dehydrogenase 2 (ALDH2) genotype.


CONCLUSIONS
The current results suggested that ESCCs developed from an epigenetic field for cancerization, which was induced by exposure to carcinogenic factors, such as tobacco smoking. The epigenetic field defect will be a novel target for risk diagnosis and prevention of ESCCs.
Oka
Daiji
D
Carcinogenesis Division, National Cancer Center Research Institute, Tokyo, Japan.
Yamashita
Satoshi
S
Tomioka
Tadashi
T
Nakanishi
Yukihiro
Y
Kato
Hoichi
H
Kaminishi
Michio
M
Ushijima
Toshikazu
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking / Q000009:adverse effects*; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D002460:Cell Line; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D004938:Esophageal Neoplasms / Q000235:genetics*; D004947:Esophagus; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009092:Mucous Membrane; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*