The Study Of Aberrant P～(16) Methylation And α-Fetoprotein MRNA In Hepatocellular Carcinoma

Background and aim: Hepatocarcinogenesis is considered to be a long-term process that comprise multiple cumulative genetic alteration, consistent with multistage nature of all late onset cancer. Loss of tumor suppressor genes function has been found in hepatocellular carcinoma (HCC). P16 is reported tumor suppressor gene, which expresses 16 KD protein, the P16 protein inhibits the binding of cyclin Dl to cyclin dependent kinases (CDK4) , preventing the phosphorylation of the retinoblastoma (Rb) protein, the underphosphorylated Rb inhibits the E2F-mediated transcriptional activation of S phase genes, which is necessary for cell proliferation. P16 is one of the central regulators that controls cell proliferation. Different inactivated mechanism of P16 gene exacts in different tumor. The mechnism of P16 gene is hypermethylation and homozygous deletion in HCC. P16 abnormalities were reported in 60% of HCC. Loss of P16 protein expression is related to the differentiation and metastasis of HCC. Recently showed that free tumor DNA is found in the plasma of cancer patients. And the presence of related oncogene or tumor suppressor gene mutation that characterized DNA in tumor cells were detected in plasma DNA. Which showed a new minitranmatized methods to diagnose or mornitor tumor, high recurrence rate in HCC mainly affected HCC prognose.monitoring early HCC recurrence helped to choise best procedure to treat HCC.our paper aimed to detect expression of P16 methylation in the plasma in HCC and evaluated P16 methylation in the plasma as molecular maker in HCC.Methods: methylation-specific-PCR(MSP) is one of best manner to display methylated tumor suppressive gene. Our paper studyed the expression of P16 gene in 35 cases HCC in the plasma,monouncleic cell,tumoral and paratumoral tissue using MSP method ,In situ hybridization and immunohistochemistry manners.Result:1. P16 methylation positive rate was detected in tumor tissue 34% and in liver cirrhosis or chronic hepatitis tissue of paratumor 11%(P<0.01). Methylation was detected in HCC with microscopic invasion to hepatic vein or lymph tube (MVT)54% and without MVT 23%(P=0.05).2. P16 methylation positive in the plasma had the same positive in HCC tumoral tissue, P16 methylation positive rate of 50% HCC tumoral tissues could be detected in the plasmas, on the contrary, P16 methylation negative in HCC tumoral tissues showed the same negative in their plasmas.3. P16 methylation positive rate of tumoral tissues and plasmas in HCC patients with early recurrence (64%,36%) showed higher than its with later recurrence (14%,5%).4. The results of P16 mRNA and P16 protein using in situ hybridization and immunohistochemistry methods were closely related to the results of P16 methylation in HCC patients,HCC patients with positive P16 methylation showed negative expression of P16 mRNA and P16 protein.5. P16 methylation positive rate in plasma was 21% in HCC patients with normal serum AFP (AFP<200ug/l) . Conclusion:1. P16 methylation could be detected in the plasmas of HCC patients, which related to HCC recurrence after surgical resection and may be useful molecular marker to monitor HCC recurrence.2. P16 methylation were closely related to P16 mRNA and P16 protein expression in HCC patients.3. P16 methylation might be related to the invasion and metastasis of HCC.4. P16 methylation in plasma might help to diagnose HCC patients with normal serum AFP(serum AFP<200ug/l) .