Epigenetic silencing of CDX2 is a feature of squamous esophageal cancer.
CDX2, a mammalian homologue of the homeobox gene 'caudal,' is expressed in gut epithelia and plays an important role in establishing the intestinal phenotype during development. Mice heterozygously disrupted for CDX2 develop disorganized polypoid hamartomas with glandular epithelium and stratified squamous metaplasia resembling foregut mucosa. Since no genetic disruptions of CDX2 have been reported to explain loss of gene function, we examined whether epigenetic mechanisms altered CDX2 expression. Eleven of 17 squamous esophageal cancer cell lines lacked expression of CDX2 that was restored following treatment with 5-aza-2'-deoxycytidine, while all colorectal cancer cell lines expressed CDX2. Loss of expression was associated with DNA methylation in the 5' region of CDX2 determined by methylation specific PCR and bisulfite sequencing. Methylation of CDX2 was rare in primary colorectal (1 of 44 tumors, 2%) and esophageal adenocarcinoma neoplasms (2 of 43 tumors, 5%), but was common in esophageal squamous carcinoma (24 of 45 tumors, 49%). No CDX2 methylation was found in normal tissues. Using semi-quantitative RT-PCR, expression of CDX2 was found in low level in normal esophagus, at higher levels in primary adenocarcinoma of the esophagus, but not in primary squamous cancers of the esophagus. Restoration of CDX2 in silenced cell lines resulted in expression of the CDX2 target gene MUC2, a gene important in glandular differentiation. Our results suggest that the inactivation of CDX2 in esophageal cancer associated with DNA methylation may be an important determinant of the squamous or non-adenomatous phenotype.
Guo
MingZhou
M
Department of Oncology, Cancer Biology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231-1000, USA.
House
Michael G
MG
Suzuki
Hiromu
H
Ye
Ying
Y
Brock
Malcolm V
MV
Lu
Fengmin
F
Liu
Zhihua
Z
Rustgi
Anil K
AK
Herman
James G
JG
D000230:Adenocarcinoma / Q000235:genetics*; D000071616:CDX2 Transcription Factor; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D003110:Colonic Neoplasms / Q000235:genetics; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics; D004938:Esophageal Neoplasms / Q000235:genetics*; D015870:Gene Expression; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D055262:Mucin-2; D009077:Mucins / Q000096:biosynthesis; D018307:Neoplasms, Squamous Cell / Q000235:genetics*; D010641:Phenotype; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D004273:DNA, Neoplasm; D018398:Homeodomain Proteins; C524625:MUC2 protein, human; C524626:Muc2 protein, mouse; D055262:Mucin-2; D009077:Mucins; D034741:RNA, Small Interfering