Promoter methylation of CDKN2A and lack of p16 expression characterize patients with hepatocellular carcinoma.
BACKGROUND
The product of CDKN2A, p16 is an essential regulator of the cell cycle controlling the entry into the S-phase. Herein, we evaluated CDKN2A promoter methylation and p16 protein expression for the differentiation of hepatocellular carcinoma (HCC) from other liver tumors.


METHODS
Tumor and corresponding non-tumor liver tissue samples were obtained from 85 patients with liver tumors. CDKN2A promoter methylation was studied using MethyLight technique and methylation-specific PCR (MSP). In the MethyLight analysis, samples with > or = 4% of PMR (percentage of methylated reference) were regarded as hypermethylated. p16 expression was evaluated by immunohistochemistry in tissue sections (n = 148) obtained from 81 patients using an immunoreactivity score (IRS) ranging from 0 (no expression) to 6 (strong expression).


RESULTS
Hypermethylation of the CDKN2A promoter was found in 23 HCCs (69.7%; mean PMR = 42.34 +/- 27.8%), six (20.7%; mean PMR = 31.85 +/- 18%) liver metastases and in the extralesional tissue of only one patient. Using MSP, 32% of the non-tumor (n = 85), 70% of the HCCs, 40% of the CCCs and 24% of the liver metastases were hypermethylated. Correspondingly, nuclear p16 expression was found immunohistochemically in five (10.9%, mean IRS = 0.5) HCCs, 23 (92%; mean IRS = 4.9) metastases and only occasionally in hepatocytes of non-lesional liver tissues (mean IRS = 1.2). The difference of CDKN2A-methylation and p16 protein expression between HCCs and liver metastases was statistically significant (p < 0.01, respectively).


CONCLUSIONS
Promoter methylation of CDKN2A gene and lack of p16 expression characterize patients with HCC.
Csepregi
Antal
A
Department of Gastroenterology, Hepatology, and Infectious Diseases, Otto-von-Guericke University, 39120 Magdeburg, Germany. csepregia@yahoo.de
Ebert
Matthias Pa
MP
Röcken
Christoph
C
Schneider-Stock
Regine
R
Hoffmann
Juliane
J
Schulz
Hans-Ulrich
HU
Roessner
Albert
A
Malfertheiner
Peter
P
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000737:chemistry* / Q000235:genetics* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000235:genetics; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000737:chemistry* / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16