Institute of Pathology and Pathophysiology, Shandong University School of Medicine, Jinan, 250012, China.
J Gastroenterol. 2013 Jan;48(1):132-43. doi: 10.1007/s00535-012-0621-0. Epub 2012 Jul 6.
Genetic and epigenetic alterations are the two key mechanisms in the development of hepatocellular carcinoma (HCC). However, how they contribute to hepatocarcinogenesis and the correlation between them has not been fully elucidated.
A total of 48 paired HCCs and noncancerous tissues were used to detect loss of heterozygosity (LOH) and the methylation profiles of five tumor suppressor genes (RASSF1A, BLU, FHIT, CRBP1, and HLTF) on chromosome 3 by using polymerase chain reaction (PCR) and methylation-specific PCR. Gene expression was analyzed by immunohistochemistry and reverse transcription (RT)-PCR.
Sixteen of 48 (33.3 %) HCCs had LOH on at least one locus on chromosome 3, and two smallest common deleted regions (3p22.3-24.3 and 3p12.3-14.2) were identified. RASSF1A, BLU, and FHIT showed very high frequencies of methylation in HCCs (100, 81.3, and 64.6 %, respectively) and noncancerous tissues, but not in liver tissues from control patients. Well-differentiated HCCs showed high methylation frequencies of these genes but very low frequencies of LOH. Furthermore, BLU methylation was associated with an increased level of alpha-fetoprotein, and FHIT methylation was inversely correlated with HCC recurrence. In comparison, CRBP1 showed moderate frequencies of methylation, while HLTF showed low frequencies of methylation, and CRBP1 methylation occurred mainly in elderly patients. Treatment with 5-aza-2'-deoxycytidine demethylated at least one of these genes and restored their expression in a DNA methylation-dependent or -independent manner.
Hypermethylation of RASSF1A, BLU, and FHIT is a common and very early event in hepatocarcinogenesis; CRBP1 methylation may also be involved in the later stage. Although LOH was not too frequent on chromosome 3, it may play a role as another mechanism in hepatocarcinogenesis.
遗传和表观遗传改变是肝细胞癌（HCC）发生的两个关键机制。然而，它们如何促进肝癌的发生以及它们之间的相关性尚未完全阐明。
使用聚合酶链反应（PCR）和甲基化特异性 PCR 检测 48 对 HCC 和非癌组织中 5 个肿瘤抑制基因（RASSF1A、BLU、FHIT、CRBP1 和 HLTF）的杂合性丢失（LOH）和甲基化谱。通过免疫组织化学和逆转录（RT）-PCR 分析基因表达。
48 例 HCC 中有 16 例（33.3%）在染色体 3 上至少有一个位点发生 LOH，鉴定出两个最小共同缺失区域（3p22.3-24.3 和 3p12.3-14.2）。RASSF1A、BLU 和 FHIT 在 HCC 和非癌组织中均显示出非常高的甲基化频率（分别为 100%、81.3%和 64.6%），但在对照患者的肝组织中未发现。高分化 HCC 显示这些基因的高甲基化频率，但 LOH 频率非常低。此外，BLU 甲基化与甲胎蛋白水平升高有关，FHIT 甲基化与 HCC 复发呈负相关。相比之下，CRBP1 显示出中等频率的甲基化，HLTF 显示出低频率的甲基化，CRBP1 甲基化主要发生在老年患者中。用 5-氮杂-2'-脱氧胞苷处理可使至少一个基因去甲基化，并以 DNA 甲基化依赖或非依赖的方式恢复其表达。
RASSF1A、BLU 和 FHIT 的高甲基化是肝癌发生过程中的一个常见且非常早期的事件；CRBP1 甲基化也可能参与晚期阶段。虽然染色体 3 上的 LOH 并不太频繁，但它可能作为另一种机制在肝癌发生中发挥作用。
