Department of Hepatobiliary and Pancreatic Surgery, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
Neoplasma. 2012;59(3):326-32. doi: 10.4149/neo_2012_042.
Secreted Frizzled-related protein 1 (sFRP1), as one of most important Wnt antagonists, is frequently silenced by promoter hypermethylation in many types of tumor, including hepatocellular carcinoma (HCC). In this study, we aimed to investigate whether restoration of sFRP1 affected HCC metastatic behavior. sFRP1 mRNA expression and promoter methylation in HCC tissues and cell lines were examined using RT-PCR and methylation-specific PCR (MS-PCR), respectively. sFRP1 protein expression was assessed by Western Blot. We generated stable HCC cell line restoration of sFRP1 in HepG2 cells, which naturally do not express detectable sFRP1 mRNA. The effects of exogenous sFRP1 on HepG2 cell invasion were investigated using trans-well assay. Also the effects of sFRP1 re-expression on the β-catenin/T-cell factor-dependent transcription activity was measured by luciferase assay.sFRP1 promoter methylation was frequently observed in HCC tissues (60%) and cell lines (75%). All samples with sFRP1 methylation showed down-regulation of sFRP1 expression in HCC cell lines. Demethylation treatment with 5-aza-20-deoxycytidine in HCC cells restored sFRP1 expression. Restoration of sFRP1 substantially impaired the invasive potentials of HepG2 cells. Moreover, exogenous sFRP1 caused significant decrease of β-catenin/T-cell factor-dependent transcription activity.These findings demonstrate that sFRP1 silencing due to promoter hypermethylation is a major event during tumorigenesis. sFRP1 is also a negative modulator of canonical Wnt signaling, which could contribute to metastasis in HCC progression, thus providing a possible therapeutic strategy against HCC.
分泌型卷曲相关蛋白 1(sFRP1)作为最重要的 Wnt 拮抗剂之一,在许多类型的肿瘤中,包括肝细胞癌(HCC),其启动子经常因高甲基化而沉默。在这项研究中,我们旨在研究 sFRP1 的恢复是否会影响 HCC 的转移行为。使用 RT-PCR 和甲基化特异性 PCR(MS-PCR)分别检测 HCC 组织和细胞系中的 sFRP1 mRNA 表达和启动子甲基化。通过 Western Blot 评估 sFRP1 蛋白表达。我们在 HepG2 细胞中生成了稳定的 HCC 细胞系 sFRP1 恢复,HepG2 细胞天然不表达可检测到的 sFRP1 mRNA。使用 Transwell 测定法研究外源性 sFRP1 对 HepG2 细胞侵袭的影响。还通过荧光素酶测定法测量 sFRP1 再表达对 β-连环蛋白/T 细胞因子依赖性转录活性的影响。sFRP1 启动子甲基化在 HCC 组织(60%)和细胞系(75%)中频繁观察到。所有 sFRP1 甲基化的样本在 HCC 细胞系中均显示 sFRP1 表达下调。用 5-氮杂-2-脱氧胞苷对 HCC 细胞进行去甲基化处理可恢复 sFRP1 表达。sFRP1 的恢复大大削弱了 HepG2 细胞的侵袭潜能。此外,外源性 sFRP1 导致 β-连环蛋白/T 细胞因子依赖性转录活性显著降低。这些发现表明,由于启动子高甲基化导致 sFRP1 沉默是肿瘤发生过程中的一个主要事件。sFRP1 也是经典 Wnt 信号的负调节剂,它可能有助于 HCC 进展中的转移,从而为 HCC 提供了一种可能的治疗策略。
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