Promoter hypermethylation contributes to frequent inactivation of a putative conditional tumor suppressor gene connective tissue growth factor in ovarian cancer
Promoter hypermethylation contributes to frequent inactivation of a putative conditional tumor suppressor gene connective tissue growth factor in ovarian cancer
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DOI：
10.1158/0008-5472.can-06-4567
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发表时间：
2007-08-01
期刊：
影响因子：
11.2
通讯作者：
Imoto, Issei
中科院分区：
文献类型：
--
作者：
Kikuchi, Ryoko;Tsuda, Hitoshi;Imoto, Issei
结缔组织生长因子（CTGF）是一种属于CCN家族的分泌蛋白，其成员参与多种生物过程。在使用内部阵列比较基因组杂交技术筛选卵巢癌细胞系基因组拷贝数畸变的过程中，我们发现了CTGF （6q23.2）的纯合缺失。在正常卵巢组织和永生化卵巢上皮细胞中观察到CTGF mRNA的表达，但在许多未纯合缺失的卵巢癌细胞系中（23个细胞系中的12个），CTGF mRNA表达减少，并在5-aza 2 '-脱氧胞苷处理后恢复。CTGF CpG岛周围的甲基化状态与表达呈负相关，甲基化的假设靶区显示启动子活性。CTGF甲基化在原发性卵巢癌组织中很常见（66,59 %），且与CTGF mRNA表达呈负相关。在原发性卵巢癌的免疫组织化学分析中，CTGF蛋白表达经常降低（103例中84例，82%）。卵巢癌在早期阶段（I期和II期）比晚期阶段（III期和IV期）更容易缺乏CTGF表达。CTGF蛋白在不同组织学亚型间的表达也存在差异。外源性恢复CTGF表达或用重组CTGF处理可抑制缺乏CTGF表达的卵巢癌细胞的生长，而敲低内源性CTGF可加速表达该基因的卵巢癌细胞的生长。这些结果表明，CTGF启动子的高甲基化导致表观遗传沉默导致CTGF功能丧失，这可能是以阶段依赖和/或组织学亚型依赖的方式参与卵巢癌癌变的一个因素。
Connective tissue growth factor (CTGF) is a secreted protein belonging to the CCN family, members of which are implicated in various biological processes. We identified a homozygous loss of CTGF (6q23.2) in the course of screening a panel of ovarian cancer cell lines for genomic copy number aberrations using in-house array-based comparative genomic hybridization. CTGF mRNA expression was observed in normal ovarian tissue and immortalized ovarian epithelial cells but was reduced in many ovarian cancer cell lines without its homozygous deletion (12 of 23 lines) and restored after treatment with 5-aza 2 '-deoxycytidine. The methylation status around the CTGF CpG island correlated inversely with the expression, and a putative target region for methylation showed promoter activity. CTGF methylation was frequently observed in primary ovarian cancer tissues (39 of 66, 59%) and inversely correlated with CTGF mRNA expression. In an immunohistochemical analysis of primary ovarian cancers, CTGF protein expression was frequently reduced (84 of 103 cases, 82%). Ovarian cancer tended to lack CTGF expression more frequently in the earlier stages (stages I and II) than the advanced stages (stages III and IV). CTGF protein was also differentially expressed among histologic subtypes. Exogenous restoration of CTGF expression or treatment with recombinant CTGF inhibited the growth of ovarian cancer cells lacking its expression, whereas knockdown of endogenous CTGF accelerated growth of ovarian cancer cells with expression of this gene. These results suggest that epigenetic silencing by hypermethylation of the CTGF promoter leads to a loss of CTGF function, which may be a factor in the carcinogenesis of ovarian cancer in a stage-dependent and/or histologic subtype-dependent manner.