Department of Medicine, Division of Hematology-Oncology, Hillman Cancer Center, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213-1863, USA.
Clin Cancer Res. 2010 Feb 15;16(4):1140-8. doi: 10.1158/1078-0432.CCR-09-2463. Epub 2010 Feb 9.
The X-linked ectodermal dysplasia receptor (XEDAR) is a novel receptor of the tumor necrosis factor receptor family that binds to ectodysplasin-A2 (EDA-A2) and induces cell death. The purpose of this study was to determine the tumor-suppressive potential of XEDAR in the development of breast cancer.
We analyzed the expression of XEDAR in breast cancer cell lines and tumor samples using quantitative real-time PCR analysis and immunoblotting. We analyzed the human XEDAR gene promoter for the presence of any CpG island and examined its methylation status using methylation-specific real-time PCR. We examined the effect of 5-aza-2'-deoxycytidine on the expression of XEDAR and sensitivity to EDA-A2-induced apoptosis in breast cancer cell lines.
Expression of XEDAR, but not EDA-A2, was downregulated in most tumorigenic breast cancer cell lines and tumor samples. Loss of XEDAR expression correlated with the hypermethylation of its promoter. Ectopic expression of XEDAR in MDA-MB-231 cells resulted in significant induction of apoptosis and reduction in colony formation. Treatment with 5-aza-2'-deoxycytidine restored XEDAR expression in breast cancer cell lines with methylated XEDAR promoter and sensitized them to EDA-A2-induced cell death.
Our results suggest that XEDAR expression is downregulated in most breast cancers via promoter methylation, which may contribute to accelerated tumor development by blocking EDA-A2-induced cell death. XEDAR may represent a novel breast tumor suppressor gene, and restoration of its expression by treatment with DNA demethylating agents may represent an attractive approach for the treatment of breast cancer.
X 连锁外胚层发育不良受体（XEDAR）是肿瘤坏死因子受体家族的一种新型受体，它与外胚层发育不良素 A2（EDA-A2）结合并诱导细胞死亡。本研究旨在确定 XEDAR 在乳腺癌发生发展中的肿瘤抑制潜能。
我们使用定量实时 PCR 分析和免疫印迹分析来分析乳腺癌细胞系和肿瘤样本中 XEDAR 的表达。我们分析了人 XEDAR 基因启动子中是否存在 CpG 岛，并使用甲基化特异性实时 PCR 检查其甲基化状态。我们研究了 5-氮杂-2'-脱氧胞苷对 XEDAR 表达的影响以及对乳腺癌细胞系中 EDA-A2 诱导细胞凋亡的敏感性。
大多数致瘤性乳腺癌细胞系和肿瘤样本中 XEDAR 的表达下调，而 EDA-A2 的表达则下调。XEDAR 表达的缺失与启动子的高甲基化有关。在 MDA-MB-231 细胞中异位表达 XEDAR 可显著诱导细胞凋亡并减少集落形成。用 5-氮杂-2'-脱氧胞苷处理可恢复甲基化 XEDAR 启动子的乳腺癌细胞系中的 XEDAR 表达，并使它们对 EDA-A2 诱导的细胞死亡敏感。
我们的研究结果表明，大多数乳腺癌中 XEDAR 的表达通过启动子甲基化下调，这可能通过阻断 EDA-A2 诱导的细胞死亡而促进肿瘤的快速发展。XEDAR 可能代表一种新型的乳腺癌肿瘤抑制基因，通过用 DNA 去甲基化剂治疗恢复其表达可能是治疗乳腺癌的一种有吸引力的方法。
