Expression of mRNA for DNA methyltransferases and methyl-CpG-binding proteins and DNA methylation status on CpG islands and pericentromeric satellite regions during human hepatocarcinogenesis.
To evaluate the significance of alterations in DNA methylation during human hepatocarcinogenesis, we examined levels of mRNA for DNA methyltransferases and methyl-CpG-binding proteins and the DNA methylation status in 67 hepatocellular carcinomas (HCCs). The average level of mRNA for DNMT1 and DNMT3a was significantly higher in noncancerous liver tissues showing chronic hepatitis or cirrhosis than in histologically normal liver tissues, and was even higher in HCCs. Significant overexpression of DNMT3b and reduced expression of DNMT2 were observed in HCCs compared with the corresponding noncancerous liver tissues. DNA hypermethylation on CpG islands of the p16 (8% and 66%) and hMLH1 (0% and 0%) genes and methylated in tumor (MINT) 1 (6% and 34%), 2 (24% and 58%), 12 (21% and 33%), 25 (0% and 5%), and 31 (0% and 23%) clones, and DNA hypomethylation on satellites 2 and 3 (18% and 67%), were detected in noncancerous liver tissues and HCCs, respectively. There was no significant correlation between the expression level of any DNA methyltransferase and DNA methylation status. Reduced expression of DNA repair protein, MBD4, was significantly correlated with poorer tumor differentiation and involvement of portal vein. Slightly reduced expression of MBD2 was detected in HCCs, and the expression of MeCP2 was particularly reduced in HCCs with portal vein involvement. These data suggest that overexpression of DNMT1 and DNMT3a, DNA hypermethylation on CpG islands, and DNA hypomethylation on pericentromeric satellite regions are early events during hepatocarcinogenesis, and that reduced expression of MBD4 may play a role in malignant progression of HCC.
Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Y
Y
Saito
Y
Y
Kanai
M
M
Sakamoto
H
H
Saito
H
H
Ishii
S
S
Hirohashi
D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D002503:Centromere / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone; D018899:CpG Islands / Q000235:genetics*; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics*; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D004276:DNA, Satellite / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D008297:Male; D051783:Methyl-CpG-Binding Protein 2; D008875:Middle Aged; D012333:RNA, Messenger / Q000378:metabolism*; D012097:Repressor Proteins; D000097584:DNA Methyltransferase 3B
D002352:Carrier Proteins; D002868:Chromosomal Proteins, Non-Histone; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D004276:DNA, Satellite; D004268:DNA-Binding Proteins; D051783:Methyl-CpG-Binding Protein 2; D012333:RNA, Messenger; D012097:Repressor Proteins; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C000715535:Dnmt3a protein, mouse; C497392:MECP2 protein, human; C491786:Dnmt2 protein, mouse; C000619380:DNMT1 protein, human; C000619381:Dnmt1 protein, mouse; C112218:TRDMT1 protein, human