Methylation-related silencing of p14ARF gene correlates with telomerase activity and mRNA expression of human telomerase reverse transcriptase in hepatocellular carcinoma.
Since loss of p16 is closely related to functional inactivation of p27 in HCC, investigating both p16 and p27 may be useful for precise prognostic predictions in individuals with HCC.
However, p16 methylation was associated with a poor survival after surgery for recurrent stage I to II hepatocellular carcinomas (hazard ratio, 4.05; 95% confidence interval, 1.15-14.20; P = 0.03).
The frequency of RASSF1A hypermethylation was much higher than that of p16INK4a and HAI2 in both HCC and neighboring tissues, indicating that deregulation of RASSF1A may precede the other two genes.
Generally, these results indicate that persistent HBV infection may be associated with high rate of p16 methylation, and involved in development of HCC through this way.
In order to clarify the significance of methylation of p16 gene promoter, we examined the methylation status of p16 gene in association with phosphorylation of retinoblastoma gene product (pRb) and cell growth in human HCC cell lines.
The status of p16INK4A was evaluated in 117 HCC tumoral nodules and 110 corresponding peritumoral tissues by loss of heterozigosity (LOH) at the 9p21-22 region, homozygous deletions, single-strand conformation polymorphism-polymerase chain reaction (PCR) mutational analysis and methylation specific PCR.
HCC samples showing low Id-1 protein expression had a lower Id-1 mRNA level (340.2 versus 1467%, P = 0.039) and higher p16INK4a expression (195 versus -78.6%, P = 0.039) than samples with high Id-1 protein expression.
Inactivation of p14(ARF) was always associated with the concomitant inactivation of p16(INK4a) and occurred more frequently in hepatitis C virus (HCV)-associated HCC (p=0.042).