Methylation framework of cell cycle gene inhibitors in cirrhosis and associated hepatocellular carcinoma.
One of the main regulatory pathways reported to be altered in hepatocellular carcinoma (HCC) is that of cell cycle control involving RB1 gene-related cell inhibitors. We investigated p14(ARF), p15(INK4B), p16(INK4A), p18(INK4C), and RB1 genes in a series of HCCs and associated cirrhosis with the goal of ascertaining their pattern of inactivation by gene methylation. Thirty-three HCCs, adjacent nonneoplastic cirrhotic tissues, and 6 HCC cell lines were studied. Cirrhoses (25 of 33, 76%), HCCs (31 of 33, 94%), and 3 of 6 (50%) cell lines showed 1 or more methylated genes. Cirrhoses (17 of 33, 51%) had more frequently than HCCs (11 of 33, 33%, P =.01) only 1 methylated gene. With the exception of p18(INK4C) the genes under study showed promoter methylation with frequency ranging from 82% (p16(INK4A) in HCC) to 33% and 39% (p15(INK4B) and p16(INK4A) in cirrhoses). In cases with only 1 methylated gene, p15(INK4B) in cirrhosis (8 of 17, 47%) and p16(INK4A) in HCC (10 of 11, 91%) were the more frequently altered. An optimal correlation was found between p15 and p16 gene methylation and complete protein loss in HCC detected by immunocytochemistry, whereas a partial loss of the same proteins was a feature of methylated cirrhoses. Inactivation by DNA methylation of several genes of the RB1 pathway is common to cirrhosis and HCC. An early pattern of methylatory events (1 methylated gene) is a feature of cirrhosis rather than HCC, whereas an advanced one (> or = 3 methylated genes) is characteristic of malignancy. Early methylation changes seem to involve p15(INK4B) and p16(INK4A) in cirrhosis and p16(INK4A) in HCC. In conclusion, a stepwise progression of methylating events is a feature of the sequence cirrhosis-HCC and contributes to the process of hepatic carcinogenesis with potential clinical implications.
Roncalli
Massimo
M
Department of Pathology and Research Laboratory, Humanitas Clinical Institute of Rozzano and University of Milan, Italy. massimo.roncalli@humaitas.it
Bianchi
Paolo
P
Bruni
Barbara
B
Laghi
Luigi
L
Destro
Annarita
A
Di Gioia
Sonia
S
Gennari
Leandro
L
Tommasini
Maurizio
M
Malesci
Alberto
A
Coggi
Guido
G
D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000503:physiopathology*; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D050763:Cyclin-Dependent Kinase Inhibitor p18; D019175:DNA Methylation; D004791:Enzyme Inhibitors; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018816:Genes, cdc / Q000502:physiology*; D006801:Humans; D008103:Liver Cirrhosis / Q000235:genetics / Q000503:physiopathology*; D008113:Liver Neoplasms / Q000235:genetics / Q000503:physiopathology*; D008297:Male; D011401:Promoter Regions, Genetic / Q000502:physiology; D016160:Retinoblastoma Protein / Q000235:genetics; D014407:Tumor Cells, Cultured; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics
C493971:CDKN2C protein, human; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050763:Cyclin-Dependent Kinase Inhibitor p18; D004791:Enzyme Inhibitors; D016160:Retinoblastoma Protein; D025803:Tumor Suppressor Protein p14ARF; D025521:Tumor Suppressor Proteins