Veeck J, Niederacher D, An H, Klopocki E, Wiesmann F, Betz B, Galm O, Camara O, Dürst M, Kristiansen G, Huszka C, Knüchel R, Dahl E
Institute of Pathology, University Hospital of the RWTH Aachen, Aachen, Germany.
Oncogene. 2006 Jun 8;25(24):3479-88. doi: 10.1038/sj.onc.1209386. Epub 2006 Jan 30.
The canonical Wnt signalling pathway plays a key role during embryogenesis and defects in this pathway have been implicated in the pathogenesis of various types of tumours, including breast cancer. The gene for secreted frizzled-related protein 1 (SFRP1) encodes a soluble Wnt antagonist and is located in a chromosomal region (8p22-p12) that is often deleted in breast cancer. In colon, lung, bladder and ovarian cancer SFRP1 expression is frequently inactivated by promoter methylation. We have previously shown that loss of SFRP1 protein expression is a common event in breast tumours that is associated with poor overall survival in patients with early breast cancer. To investigate the cause of SFRP1 loss in breast cancer, we performed mutation, methylation and expression analysis in human primary breast tumours and breast cell lines. No SFRP1 gene mutations were detected. However, promoter methylation of SFRP1 was frequently observed in both primary breast cancer (61%, n=130) and cell lines analysed by methylation-specific polymerase chain reaction (MSP). We found a tight correlation (P<0.001) between methylation and loss of SFRP1 expression in primary breast cancer tissue. SFRP1 expression was restored after treatment of tumour cell lines with the demethylating agent 5-aza-2'-deoxycytidine. Most interestingly, SFRP1 promoter methylation was an independent factor for adverse patient survival in Kaplan-Meier analysis. Our results indicate that promoter hypermethylation is the predominant mechanism of SFRP1 gene silencing in human breast cancer and that SFRP1 gene inactivation in breast cancer is associated with unfavourable prognosis.
经典Wnt信号通路在胚胎发育过程中起关键作用，该通路的缺陷与包括乳腺癌在内的多种肿瘤的发病机制有关。分泌型卷曲相关蛋白1（SFRP1）基因编码一种可溶性Wnt拮抗剂，位于染色体区域（8p22 - p12），该区域在乳腺癌中常发生缺失。在结肠癌、肺癌、膀胱癌和卵巢癌中，SFRP1表达常因启动子甲基化而失活。我们之前已经表明，SFRP1蛋白表达缺失在乳腺肿瘤中是常见事件，与早期乳腺癌患者的总体生存率低相关。为了研究乳腺癌中SFRP1缺失的原因，我们对人原发性乳腺肿瘤和乳腺细胞系进行了突变、甲基化和表达分析。未检测到SFRP1基因突变。然而，通过甲基化特异性聚合酶链反应（MSP）分析发现，原发性乳腺癌（61%，n = 130）和细胞系中均频繁观察到SFRP1启动子甲基化。我们发现原发性乳腺癌组织中甲基化与SFRP1表达缺失之间存在紧密相关性（P < 0.001）。用去甲基化剂5 - 氮杂 - 2'-脱氧胞苷处理肿瘤细胞系后，SFRP1表达得以恢复。最有趣的是，在Kaplan - Meier分析中，SFRP1启动子甲基化是患者不良生存的独立因素。我们的结果表明，启动子高甲基化是人类乳腺癌中SFRP1基因沉默的主要机制，并且乳腺癌中SFRP1基因失活与不良预后相关。
