Novel epigenetic paradigm in endometrial cancer recurrence

描述（由申请人提供）：已知启动子CpG岛的DNA超甲基化与子宫内膜癌中的转录沉默相关。我们最近鉴定了一组独特的CpG岛基因座，其在非复发性肿瘤中高甲基化，但在随后复发的原发性肿瘤中协调地低甲基化（或较少甲基化）。所述基因座可能对从头DNA甲基化高度敏感（即，默认状态）部分归因于DNA甲基转移酶1（DNMT 1）和多梳阻遏复合物2（PRC 2）的高表达。虽然这些基因座与上皮-间充质转化（EMT）有关，但通常不在正常细胞中表达，但它们的染色质可能保持在与干细胞和祖细胞中观察到的类似的二价状态。将这些位点与表皮生长因子受体（EGFR）信号联系起来的基于网络的分析表明，低DNA甲基化特征和允许的染色质状态可以允许通过该途径进行转录激活。我们的功能研究证实了这一点，表明EGF通过上皮粘附标记物（EpCAM）细胞内结构域（EpICD）诱导候选基因的表达。我们假设EpICD转录复合物在靶启动子处的结合限制了DNMT1/PRC2进入这些位点，并招募组蛋白甲基转移酶将染色质修饰为复发性肿瘤中的活性状态。这种默认状态的表观遗传学改变对于EMT介导的子宫内膜癌细胞的进展是必要的。在目标1中，我们将在一个独立的子宫内膜癌队列中验证这些候选基因座的甲基化状态。这些位点的DNA低甲基化和过表达可作为预测患者子宫内膜癌复发风险的生物标志物。在目标2中，我们将评估EGF诱导的EMT是否导致鉴定描绘新的候选低甲基化因子的EpICD靶基因。EGF诱导的细胞的相关间充质特征将通过分子手段和指示增加的侵袭性的细胞纳米力学特征来检查。在目标3中，我们将确定EpICD转录复合物是否是这种表观遗传重编程的关键因素。预期EpICD与靶启动子的结合会减少DNMT1/PRC2的结合，并改变组蛋白标记的组合模式，从而为EMT介导的转录指定活性染色质状态。

DESCRIPTION (provided by applicant): DNA hypermethylation of promoter CpG islands is known to be associated with transcriptional silencing in endometrial cancer. We recently identified a unique set of CpG island loci that are hypermethylated in non- recurrent tumors but coordinately hypomethylated (or less methylated) in primary tumors that subsequently recurred. The loci can be highly susceptible to de novo DNA methylation (i.e., a default state) partly attributed to the high expression of DNA methyltransferase 1 (DNMT1) and Polycomb Repressor Complex 2 (PRC2). While these loci, which are implicated in epithelial-mesenchymal transition (EMT), are not usually expressed in normal cells, their chromatin may remain in a bivalent state similar to those observed in stem and progenitor cells. Network-based analysis linking these loci to epidermal growth factor receptor (EGFR) signaling suggests that a low DNA methylation signature and a permissive chromatin state can permit transcriptional activation by this pathway. This was confirmed by our functional studies showing that EGF induced the expression of candidate genes via the epithelial adhesion marker (EpCAM) intracellular domain (EpICD). We hypothesize that the binding of EpICD transcriptional complex at target promoters limits the access of DNMT1/PRC2 to these loci and recruits histone methyltransferases to modify the chromatin into an active state in recurrent tumors. This epigenetic overwriting of the default state is necessary for EMT-mediated progression of endometrial cancer cells. In Aim 1, we will validate the methylation status of these candidate loci in an independent cohort of endometrial cancer. DNA hypomethylation and over-expression of these loci can be used as biomarkers for predicting risk of endometrial cancer recurrence in patients. In Aim 2, we will assess whether EGF-induced EMT leads to identification of EpICD target genes delineating novel candidate hypomethylators. Associated mesenchymal characteristics of EGF-induced cells will be examined by molecular means and cellular nanomechanical features indicative of increased invasiveness. In Aim 3, we will determine whether the EpICD transcription complex is a key factor of this epigenetic reprogramming. EpICD binding to target promoters is expected to diminish the binding of DNMT1/PRC2 and alter combinatorial patterns of histone marks specifying an active chromatin state for EMT-mediate transcription.