Department of Histology and Cell Biology, Nagasaki University Graduate School of Biomedical Science, Nagasaki, Japan.
Int J Oncol. 2013 Nov;43(5):1467-80. doi: 10.3892/ijo.2013.2062. Epub 2013 Aug 20.
Epigenetic parameters such as DNA methylation and histone modifications play pivotal roles in carcinogenesis. Global histone modification patterns have been implicated as possible predictors of cancer recurrence and prognoses in a great variety of tumor entities. Our study was designed to evaluate the association among trimethylated histone H3 at lysine 27 (H3K27me3), clinicopathological variables and outcome in early-stage non-small cell lung cancer (NSCLC). The expression of H3K27me3 and its methyl-transferase, enhancer of zeste homolog 2 (EZH2) together with proliferating cell nuclear antigen (PCNA) were evaluated by immunohistochemistry in normal lung tissue (n=5) and resected NSCLC patients (n=42). In addition, the specificity of antibody for H3K27me3 was tested by western blot analysis. The optimal cut-off point of H3K27me3 expression for prognosis was determined by the X-tile program. The prognostic significance was determined by means of Kaplan-Meier survival estimates and log-rank tests. As a result, enhanced trimethylation of H3K27me3 was correlated with longer overall survival (OS) and better prognosis (P<0.05). Moreover, both univariate and multivariate analyses indicated that H3K27me3 level was a significant and independent predictor of better survival (hazard ratio, 0.187; 95% confidence interval, 0.066-0.531, P=0.002). Furthermore, H3K27me3 expression was positively correlated with DNA methylation level at CCGG sites while reversely related to EZH2 expression (P<0.05). In conclusion, H3K27me3 level defines unrecognized subgroups of NSCLC patients with distinct epigenetic phenotype and clinical outcome, and can probably be used as a novel predictor for better prognosis in NSCLC patients.
表观遗传参数，如 DNA 甲基化和组蛋白修饰，在癌症发生中起着关键作用。广泛的组蛋白修饰模式被认为是多种肿瘤实体中癌症复发和预后的可能预测因子。我们的研究旨在评估三甲基化组蛋白 H3 赖氨酸 27（H3K27me3）与早期非小细胞肺癌（NSCLC）的临床病理变量和结果之间的关系。通过免疫组织化学方法在正常肺组织（n=5）和切除的 NSCLC 患者（n=42）中评估 H3K27me3 及其甲基转移酶，EZH2 同源物 2（EZH2）和增殖细胞核抗原（PCNA）的表达。此外，通过 Western blot 分析测试了 H3K27me3 抗体的特异性。通过 X-tile 程序确定 H3K27me3 表达的最佳预后截断点。通过 Kaplan-Meier 生存估计和对数秩检验确定预后的意义。结果表明，H3K27me3 的增强甲基化与更长的总生存期（OS）和更好的预后相关（P<0.05）。此外，单因素和多因素分析均表明 H3K27me3 水平是生存的显著和独立预测因子（危险比，0.187；95%置信区间，0.066-0.531，P=0.002）。此外，H3K27me3 表达与 CCGG 位点的 DNA 甲基化水平呈正相关，而与 EZH2 表达呈负相关（P<0.05）。总之，H3K27me3 水平定义了具有不同表观遗传表型和临床结果的 NSCLC 患者的未识别亚组，并且可能被用作 NSCLC 患者预后更好的新预测因子。
