Genome-wide analysis of epigenetic silencing identifies BEX1 and BEX2 as candidate tumor suppressor genes in malignant glioma
Genome-wide analysis of epigenetic silencing identifies BEX1 and BEX2 as candidate tumor suppressor genes in malignant glioma
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DOI：
10.1158/0008-5472.can-05-4453
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发表时间：
2006-07-01
期刊：
影响因子：
11.2
通讯作者：
Madan, Anup
中科院分区：
文献类型：
--
作者：
Foltz, Greg;Ryu, Gi-Yung;Madan, Anup
启动子超甲基化和组蛋白去乙酰化是人类癌症中肿瘤抑制基因转录沉默的常见表观遗传机制。我们用组蛋白去乙酰化酶抑制剂trichostatin A （TSA）或DNA甲基转移酶抑制剂5-aza-2′-脱氧胞苷（5-AzaC）处理了两种永生化胶质瘤细胞系T98和U87，以及10种患者来源的原发性胶质瘤细胞系，以全面确定通过这些不同但相关的表观遗传过程的药理学逆转而重新激活的基因队列。全基因组微阵列分析鉴定了TSA（653）或5-AzaC处理（170）诱导的基因。我们选择了一组再激活基因，这些基因在大多数胶质瘤细胞系中经TSA或5-AzaC处理后被显著诱导（大于两倍），而在培养的正常星形胶质细胞中则没有。然后，我们在组织学证实的人类肿瘤和非肿瘤脑标本中表征了启动子甲基化程度和选定基因的转录沉默。我们发现了两个新的脑表达基因，BEX1和BEX2，它们在所有肿瘤标本中沉默，并表现出广泛的启动子超甲基化。在体外和异种移植小鼠模型中，病毒介导的BEX1或BEX2的再表达导致对化疗诱导的细胞凋亡的敏感性增加和有效的肿瘤抑制作用。利用综合方法，我们建立了一个新的平台，用于恶性胶质瘤中表观遗传沉默基因的全基因组筛选。这一实验模式为鉴定表观遗传沉默基因提供了一种强有力的新方法，这些基因具有肿瘤抑制、疾病诊断和检测的生物标志物以及在胶质瘤发病过程中重要的关键调控途径的治疗可逆调节剂的潜在功能。
Promoter hypermethylation and histone deacetylation are common epigenetic mechanisms implicated in the transcriptional silencing of tumor suppressor genes in human cancer. We treated two immortalized glioma cell lines, T98 and U87, and 10 patient-derived primary glioma cell lines with trichostatin A (TSA), a histone deacetylase inhibitor, or 5-aza-2'-deoxycytidine (5-AzaC), a DNA methyltransferase inhibitor, to comprehensively identify the cohort of genes reactivated through the pharmacologic reversal of these distinct but related epigenetic processes. Whole-genome microarray analysis identified genes induced by TSA (653) or 5-AzaC treatment (170). We selected a subset of reactivated genes that were markedly induced (greater than two-fold) after treatment with either TSA or 5-AzaC in a majority of glioma cell lines but not in cultured normal astrocytes. We then characterized the degree of promoter methylation and transcriptional silencing of selected genes in histologically confirmed human tumor and nontumor brain specimens. We identified two novel brain expressed genes, BEX1 and BEX2, which were silenced in all tumor specimens and exhibited extensive promoter hypermethylation. Viral-mediated reexpression of either BEX1 or BEX2 led to increased sensitivity to chemotherapy-induced apoptosis and potent tumor suppressor effects in vitro and in a xenograft mouse model. Using an integrated approach, we have established a novel platform for the genome-wide screening of epigenetically silenced genes in malignant glioma. This experimental paradigm provides a powerful new method for the identification of epigenetically silenced genes with potential function as tumor suppressors, biomarkers for disease diagnosis and detection, and therapeutically reversible modulators of critical regulatory pathways important in glioma pathogenesis.