Division of Gastroenterology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taiwan.
J Gastroenterol Hepatol. 2013 Mar;28(3):551-9. doi: 10.1111/jgh.12078.
Except for genetic mutations, epigenetic changes are also involved in the development of human cancers. Recently, we have identified SOX1, SRY (sex determining region Y)-box 1, is hypermethylated in cervical cancer and ovarian cancer. Therefore, we investigated whether promoter hypermethylation of SOX1 is common in hepatocellular carcinoma (HCC).
We used methylation-specific polymerase chain reaction (MS-PCR) and bisulfite sequencing to analyze the methyaltion level of the SOX1 promoter in seven HCC cell lines, 54 clinical HCCs, 42 cirrhotic livers, 21 livers with chronic hepatitis, and 15 control livers. Then, we employed quantitative MS-PCR (QMSP) to validate in an independent set of samples (60 paired HCCs and 30 control livers). Finally, we used luciferase reporter and colony formation assay to check the effect of SOX1 in HCC.
Promoter methylation of SOX1 was significantly frequent in HCC cell lines and clinical HCCs, cirrhotic livers, but not in control livers (P < 0.0001). There is a significant correlation between downregulation of SOX1 expression and promoter methylation. QMSP results confirmed that promoter hypermethylation of SOX1 is significantly more frequent in HCCs than control livers (P < 0.0001). The frequency of SOX1 methylation in patients with secreted frizzled-related proteins (SFRPs) methylation is significantly higher than in patients without SFRPs methylation (P < 0.0001). Furthermore, ectopic expression of SOX1 could suppress T-cell factor-dependent transcriptional activity and colony formation number in HCCs.
Concomitant epigenetic silencing of SOX1 and SFRPs through promoter hypermethylation is frequent in HCCs, and this might contribute to abnormal activation of canonical Wnt signal pathway.
除了基因突变，表观遗传改变也参与了人类癌症的发生。最近，我们发现 SOX1（性别决定区 Y 框 1）在宫颈癌和卵巢癌中发生超甲基化。因此，我们研究了 SOX1 启动子的高甲基化是否在肝细胞癌（HCC）中普遍存在。
我们使用甲基化特异性聚合酶链反应（MS-PCR）和亚硫酸氢盐测序分析了 7 种 HCC 细胞系、54 例临床 HCC、42 例肝硬化肝、21 例慢性肝炎肝和 15 例对照肝中 SOX1 启动子的甲基化水平。然后，我们在另一组独立样本（60 对 HCC 和 30 例对照肝）中使用定量 MS-PCR（QMSP）进行验证。最后，我们使用荧光素酶报告基因和集落形成实验来检查 SOX1 在 HCC 中的作用。
SOX1 启动子甲基化在 HCC 细胞系和临床 HCC、肝硬化肝中显著频繁，但在对照肝中不频繁（P<0.0001）。SOX1 表达下调与启动子甲基化显著相关。QMSP 结果证实 SOX1 启动子的高甲基化在 HCC 中比对照肝中更为频繁（P<0.0001）。SOX1 甲基化的频率在 SFRPs 甲基化的患者中明显高于无 SFRPs 甲基化的患者（P<0.0001）。此外，SOX1 的异位表达可抑制 HCC 中 T 细胞因子依赖性转录活性和集落形成数量。
SOX1 和 SFRPs 通过启动子高甲基化的协同表观遗传沉默在 HCC 中频繁发生，这可能导致经典 Wnt 信号通路的异常激活。
