Quantitative analysis of tumor-derived methylated p16INK4a sequences in plasma, serum, and blood cells of hepatocellular carcinoma patients.
OBJECTIVE
Using real-time quantitative methylation-specific PCR (RTQ-MSP), we quantified methylated p16INK4a sequences and determined the fractional concentrations of circulating tumor DNA in plasma, serum, and peripheral blood cells collected preoperatively, intraoperatively, and postoperatively from 49 patients with hepatocellular carcinoma (HCC).


RESULTS
RTQ-MSP was sufficiently sensitive to detect down to 10 genome-equivalents of methylated p16INK4a sequences. Quantitative MSP data were expressed in terms of the methylation index, which was the percentage of bisulfite converted unmethylated and methylated p16INK4a sequences that consisted of methylated p16INK4a sequences. Quantities of methylated p16INK4a sequences were detected in peripheral circulation of 80% (23 of 29) of HCC patients. No significant difference was seen in the detectability and concentrations of methylated p16INK4a sequences (range: 10-4046 genome-equivalents/ml) between preoperative plasma and serum samples from HCC patients. Preoperatively, the p16INK4a methylation indices ranged from 0.2 to 100% and from 0.012 to 0.075% in the patients' plasma and buffy coat samples, respectively. After surgical resection, the median p16INK4a methylation indices in plasma and buffy coat concordantly decreased 12- and 15-fold, respectively. These results demonstrated the clinical usefulness and effectiveness of peripheral blood RTQ-MSP for detecting and monitoring HCC after treatment. Furthermore, none of the intraoperative plasma samples and only two of the intraoperative buffy coat samples were p16INK4a methylation positive.


CONCLUSIONS
Quantification of epigenetic changes in peripheral blood by RTQ-MSP is useful for the detection and monitoring of HCC.
Wong
Ivy H N
IH
Department of Biochemistry, Faculty of Medicine Building, Laboratory Block, The University of Hong Kong, Hong Kong, People's Republic of China.
Zhang
Jun
J
Lai
Paul B S
PB
Lau
Wan Y
WY
Lo
Y M Dennis
YM
D017209:Apoptosis; D014408:Biomarkers, Tumor; D006528:Carcinoma, Hepatocellular / Q000097:blood* / Q000378:metabolism*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis* / Q000235:genetics*; D019175:DNA Methylation; D006801:Humans; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000097:blood* / Q000378:metabolism*; D009362:Neoplasm Metastasis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D013447:Sulfites / Q000494:pharmacology; D013997:Time Factors
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D013447:Sulfites