Promoter hypomethylation of a novel cancer/testis antigen gene CAGE is correlated with its aberrant expression and is seen in premalignant stage of gastric carcinoma.
Previously, we reported the identification and characterization of a novel cancer/testis antigen gene, CAGE(4), that was expressed in various histological types of tumors, but not in normal tissues, with the exception of the testis. To date, molecular mechanisms for the expression of CAGE have never been studied. In our expression analysis, we found that some cancer cell lines did not express CAGE. The expression of CAGE could be restored in these cell lines by treatment with 5(')-aza-2(')-deoxycytidine, suggesting that the expression of CAGE is mainly suppressed by hypermethylation. Bisulfite sequencing analysis of the 16 CpG sites of the CAGE promoter in various cancer cell lines and tissues revealed a close relationship between the methylation status of the CAGE promoter and the expression of CAGE. The transient transfection experiments displayed that the methylation of CpG sites inhibited the CAGE promoter activity in luciferase reporter assays. The methylation of the CpG sites inhibited the binding of transcription factors, shown by a mobility shift assay. A methylation-specific PCR analysis revealed that hypomethylation of the CAGE promoter was present at frequencies of more than 60% in breast, gastric, and lung cancers, and hepatocellular carcinomas, and at frequencies of less than 40% in prostate, uterine cervical, and laryngeal cancers. Promoter hypomethylation was found in chronic gastritis (19/55, 34.5%) and liver cirrhosis (13/22, 59%), but not in normal prostate, normal colon, or chronic hepatitis. These results suggest that the methylation status of the CpG sites of CAGE determines its expression, that the hypomethylation of CAGE precedes the development of gastric cancer and hepatocellular carcinoma, and that the high frequencies of hypomethylation of CAGE, in various cancers would be valuable as a cancer diagnostic marker.
Cho
Bomsoo
B
Cancer Genomics Division, In2Gen Company, 110-799, Seoul, Republic of Korea.
Lee
Hansoo
H
Jeong
ShinWu
S
Bang
Yung-Jue
YJ
Lee
Hyun Joo
HJ
Hwang
Kyu Sang
KS
Kim
Hae-Yeong
HY
Lee
Yun-Sil
YS
Kang
Gyeong Hoon
GH
Jeoung
Doo-Il
DI
D034961:Antigens, Nuclear; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000378:metabolism; D001483:Base Sequence; D014408:Biomarkers, Tumor; D018899:CpG Islands; D053487:DEAD-box RNA Helicases; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006877:Hydroxamic Acids / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D009367:Neoplasm Staging; D009687:Nuclear Proteins / Q000235:genetics*; D015345:Oligonucleotide Probes / Q000378:metabolism; D011230:Precancerous Conditions; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics / Q000473:pathology*; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
D034961:Antigens, Nuclear; D000964:Antimetabolites, Antineoplastic; D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D009687:Nuclear Proteins; D015345:Oligonucleotide Probes; D014157:Transcription Factors; C012589:trichostatin A; D000077209:Decitabine; C454199:DDX53 protein, human; D053487:DEAD-box RNA Helicases; D001374:Azacitidine