Hypermethylation-associated inactivation of retinoic acid receptor beta in human esophageal squamous cell carcinoma.
OBJECTIVE
The purpose of this study was to investigate the mechanism of altered retinoic acid receptor beta (RARbeta) expression during esophageal squamous carcinogenesis.


METHODS
Samples were collected from Linzhou, China. The hypermethylation of CpG islands in the promoter region of the RARbeta gene was examined by methylation-specific PCR in human esophageal squamous cell carcinoma (ESCC) samples, as well as in neighboring tissues with normal epithelium, basal cell hyperplasia, and dysplasia. RARbeta mRNA expression was determined by in situ hybridization. The DNA methyltransferase inhibitor 2'-deoxy-5-azacytidine was used to treat the ESCC cell line, and the DNA hypermethylation status and mRNA expression level were examined.


RESULTS
Two of 17 (12%) normal, 9 of 21 basal cell hyperplasia (43%), 7 of 12 dysplasia (58%), and 14 of 20 ESCC (70%) samples had hypermethylation of the RARbeta promoter region. The loss of RARbeta mRNA expression was highly concordant with RARbeta promoter CpG island hypermethylation when individual samples were considered in the correlation analysis. Good statistical correlation between hypermethylation and loss of RARbeta expression was revealed. Frequencies of hypermethylation appeared to increase with the progression of carcinogenesis. In samples from the same patients, if hypermethylation was detected in earlier lesions, it was usually observed in more severe lesions. In the ESCC cell line KYSE 510, 2'-deoxy-5-azacytidine partially reversed CpG island hypermethylation and restored RARbeta mRNA expression.


CONCLUSIONS
The results suggest that hypermethylation of RARbeta promoter region is an important mechanism for RARbeta gene silencing in esophageal squamous carcinogenesis.
Wang
Yimin
Y
Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8020, USA.
Fang
Ming Zhu
MZ
Liao
Jie
J
Yang
Guang-Yu
GY
Nie
Yan
Y
Song
Yunlong
Y
So
Chi
C
Xu
Xiaochun
X
Wang
Li-Dong
LD
Yang
Chung S
CS
D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism; D018899:CpG Islands; D019175:DNA Methylation; D017931:DNA Primers; D015536:Down-Regulation; D004848:Epithelium / Q000378:metabolism; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D017403:In Situ Hybridization; D011230:Precancerous Conditions / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; C082925:retinoic acid receptor beta