Araújo Oscar C, Rosa Agatha S, Fernandes Arlete, Niel Christian, Villela-Nogueira Cristiane A, Pannain Vera, Araujo Natalia M
Laboratory of Molecular Virology, Oswaldo Cruz Institute, FIOCRUZ, Rio de Janeiro, Brazil.
Department of Pathology, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
PLoS One. 2016 Apr 14;11(4):e0153796. doi: 10.1371/journal.pone.0153796. eCollection 2016.
Hepatocellular carcinoma (HCC) is the second most common cause of cancer mortality worldwide. Most cases of HCC are associated with cirrhosis related to chronic hepatitis B virus or hepatitis C virus infections. Hypermethylation of promoter regions is the main epigenetic mechanism of gene silencing and has been involved in HCC development. The aim of this study was to determine whether aberrant methylation of RASSF1A and DOK1 gene promoters is associated with the progression of liver disease in Brazilian patients. Methylation levels were measured by pyrosequencing in 41 (20 HCC, 9 cirrhotic, and 12 non-cirrhotic) liver tissue samples. Mean rates of methylation in RASSF1A and DOK1 were 16.2% and 12.0% in non-cirrhotic, 26.1% and 19.6% in cirrhotic, and 59.1% and 56.0% in HCC tissues, respectively, showing a gradual increase according to the progression of the disease, with significantly higher levels in tumor tissues. In addition, hypermethylation of RASSF1A and DOK1 was found in the vast majority (88%) of the HCC cases. Interestingly, DOK1 methylation levels in HCC samples were significantly higher in the group of younger (<40 years) patients, and higher in moderately differentiated than in poorly differentiated tumors (p < 0.05). Our results reinforce the hypothesis that hypermethylation of RASSF1A and DOK1 contributes to hepatocarcinogenesis and is associated to clinicopathological characteristics. RASSF1A and DOK1 promoter hypermethylation may be a valuable biomarker for early diagnosis of HCC and a potential molecular target for epigenetic-based therapy.
肝细胞癌（HCC）是全球癌症死亡的第二大常见原因。大多数HCC病例与慢性乙型肝炎病毒或丙型肝炎病毒感染相关的肝硬化有关。启动子区域的高甲基化是基因沉默的主要表观遗传机制，并参与了HCC的发生发展。本研究的目的是确定RASSF1A和DOK1基因启动子的异常甲基化是否与巴西患者的肝病进展相关。通过焦磷酸测序法测量了41份（20份HCC、9份肝硬化和12份非肝硬化）肝组织样本中的甲基化水平。RASSF1A和DOK1在非肝硬化组织中的平均甲基化率分别为16.2%和12.0%，在肝硬化组织中分别为26.1%和19.6%，在HCC组织中分别为59.1%和56.0%，显示随着疾病进展逐渐升高，肿瘤组织中的水平显著更高。此外，在绝大多数（88%）HCC病例中发现了RASSF1A和DOK1的高甲基化。有趣的是，在年龄较小（<40岁）的HCC患者组中，HCC样本中DOK1的甲基化水平显著更高，且在中度分化肿瘤中高于低分化肿瘤（p<0.05）。我们的结果强化了这样的假设，即RASSF1A和DOK1的高甲基化促成肝癌发生，并与临床病理特征相关。RASSF1A和DOK1启动子高甲基化可能是HCC早期诊断的有价值生物标志物以及基于表观遗传学治疗的潜在分子靶点。
