Laboratory of Cellular and Molecular Engineering 'S. Cavalcanti', University of Bologna, Cesena, Italy.
Oncol Rep. 2012 Dec;28(6):2271-7. doi: 10.3892/or.2012.2047. Epub 2012 Sep 20.
We previously described a cohort of grade II oligodendroglioma (OII) patients, in whom the loss of heterozygosity (LOH) 19q was present in the subgroup at a higher risk of relapse. In this study, we evaluated the CpG methylation of the putative tumor suppressor epithelial membrane protein 3 (EMP3, 19q13.3) gene promoter in the same OII cohort, to investigate whether a correlation could be found between EMP3 cytogenetic and epigenetic loss and higher risk of relapse. Twenty-three tumor samples from OII patients were collected over a period of 10 years. Seventeen glioblastoma (GBM) samples (2 of which were relapses) were collected from 15 patients. The EMP3, O6-methylguanine methyltransferase (MGMT) and cyclooxygenase 2 (COX2) promoter methylation, evaluated by methylation-specific PCR, and the isocitrate dehydrogenase 1 (IDH1) mutation, identified by sequencing, were compared between the OII and GBM histotypes. The EMP3 promoter methylation was correlated with the analysis of LOH 19q, performed by microsatellite amplification, in OII patients. Disease progression-free interval was evaluated in the OII patients with the EMP3 methylation with either LOH 19q or conserved chromosome 19 arms. The EMP3 and MGMT promoter methylation was more frequent in OII than in GBM patients, and the IDH1 mutation was absent in GBM. The COX2 promoter was unmethylated in both histotypes. Both LOH+/- 19q OII patients showed EMP3 hypermethylation. Concomitant LOH 19q and EMP3 gene promoter methylation was observed in the OII patients at a higher risk of relapse. Our results suggest that a total (cytogenetic and epigenetic) functional loss of both EMP3 alleles accounts for the reduced disease progression-free interval in OII patients. Although the small sample size limits the strength of this study, our results support testing this hypothesis in larger cohorts of patients, considering the methylation of the EMP3 gene promoter together with LOH 19q as an indication for treatment with adjuvant therapy ab initio in order to improve the overall survival of OII patients.
我们之前描述了一组二级少突胶质细胞瘤 (OII) 患者，其中亚组存在杂合性缺失 (LOH) 19q 的患者复发风险较高。在这项研究中，我们评估了同一 OII 队列中假定的肿瘤抑制因子上皮膜蛋白 3 (EMP3，19q13.3) 基因启动子的 CpG 甲基化，以研究 EMP3 细胞遗传学和表观遗传学缺失与更高的复发风险之间是否存在相关性。在 10 年的时间内收集了来自 23 名 OII 患者的肿瘤样本。从 15 名患者中收集了 17 例胶质母细胞瘤 (GBM) 样本 (其中 2 例为复发)。通过甲基化特异性 PCR 评估 EMP3、O6-甲基鸟嘌呤甲基转移酶 (MGMT) 和环氧化酶 2 (COX2) 启动子甲基化，通过测序鉴定异柠檬酸脱氢酶 1 (IDH1) 突变，并比较 OII 和 GBM 组织型之间的差异。在 OII 患者中，通过微卫星扩增分析 LOH 19q 与 EMP3 启动子甲基化相关。在 OII 患者中，通过 EMP3 甲基化与 LOH 19q 或保守的 19 号染色体臂评估疾病无进展生存期。与 GBM 患者相比，OII 患者的 EMP3 和 MGMT 启动子甲基化更为常见，而 GBM 患者中不存在 IDH1 突变。两种组织型的 COX2 启动子均未甲基化。LOH+/-19q 的 OII 患者均表现出 EMP3 过度甲基化。在复发风险较高的 OII 患者中，观察到 LOH 19q 和 EMP3 基因启动子甲基化的同时发生。我们的结果表明，EMP3 等位基因的总（细胞遗传学和表观遗传学）功能丧失导致 OII 患者的疾病无进展生存期缩短。尽管小样本量限制了本研究的强度，但我们的结果支持在更大的患者队列中检验这一假设，考虑到 EMP3 基因启动子的甲基化以及 LOH 19q 作为辅助治疗起始时的治疗指征，以提高 OII 患者的总体生存率。
