Novel epigenetic paradigm in endometrial cancer recurrence

描述(申请人提供)：已知在子宫内膜癌中，启动子CpG岛的DNA高甲基化与转录沉默有关。我们最近发现了一组独特的CpG岛基因座，它们在未复发的肿瘤中高甲基化，但在随后复发的原发肿瘤中协调低甲基化(或较低甲基化)。这些基因座可能对从头DNA甲基化(即默认状态)高度敏感，部分原因是DNA甲基转移酶1(DNMT1)和多梳抑制物复合体2(PRC2)的高表达。虽然这些与上皮-间充质转化(EMT)有关的基因座在正常细胞中通常不表达，但它们的染色质可能保持与在干细胞和祖细胞中观察到的类似的二价态。将这些基因座与表皮生长因子受体(EGFR)信号联系起来的网络分析表明，低DNA甲基化信号和允许的染色质状态可以允许通过这一途径进行转录激活。我们的功能研究证实了这一点，研究表明EGF通过上皮黏附标记(EpCAM)胞内域(EpICD)诱导候选基因的表达。我们假设，EpICD转录复合体与靶启动子的结合限制了DNMT1/PRC2对这些基因座的访问，并招募了组蛋白甲基转移酶来将复发性肿瘤中的染色质修饰为活性状态。这种对默认状态的表观遗传重写对于EMT介导的子宫内膜癌细胞的进展是必要的。在目标1中，我们将验证这些候选基因在一个独立的子宫内膜癌队列中的甲基化状态。这些基因的DNA低甲基化和高表达可作为预测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是否导致识别描绘新的候选低甲基化的EpICD靶基因。EGF诱导细胞的相关间质特征将通过分子手段和细胞纳米力学特征来检测，这些特征表明侵袭性增加。在目标3中，我们将确定EpICD转录复合体是否是这种表观遗传重新编程的关键因素。EpICD与靶启动子的结合有望减少DNMT1/PRC2的结合，并改变组蛋白标记的组合模式，为EMT介导的转录指定活跃的染色质状态。

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.