Supplementary Material for: Epigenetic Silencing of the MLH1 Promoter in Relation to the Development of Gastric Cancer and its use as a Biomarker for Patients with Microsatellite Instability: a Systematic Analysis

<b><i>Background/Aims:</i></b> Human mutL homolog 1 (<i>MLH1</i>) promoter methylation was reported in gastric cancer (GC). This study determined the clinicopathological, prognostic, and diagnostic effects of <i>MLH1</i> promoter methylation in GC. <b><i>Methods:</i></b> The combined odds ratio (OR) or hazard ratio (HR) and their corresponding 95% confidence intervals (95% CI) were calculated. The pooled sensitivity, specificity, and area under the curve (AUC) were analyzed. <b><i>Results:</i></b> A total of 4654 GC patients and 3669 non-malignant controls were identified in this systematic analysis. <i>MLH1</i> promoter methylation was significantly higher in GC samples than in gastric adenomas, chronic gastritis, adjacent tissues, normal gastric mucosa, and normal healthy blood samples, but it exhibited a similar frequency in GC vs. intestinal metaplasia and dysplasia samples. <i>MLH1</i> promoter methylation correlated with age and microsatellite instability (MSI), but it was not associated with gender, <i>H. pylori</i> infection, smoking, drinking behaviors, pathological histology, tumor differentiation, clinical stage, lymph node status, distant metastasis, or overall survival of GC. <i>MLH1</i> promoter methylation exhibited a poor sensitivity value (&lt; 0.5) in patients with GC compared with adjacent tissues, gastric adenomas, chronic gastritis, normal gastric mucosa, and normal healthy blood samples. The pooled sensitivity, specificity, and AUC of <i>MLH1</i> promoter methylation in GC with MSI vs. GC with microsatellite stability (MSS) samples were 0.64, 0.96, and 0.90, respectively. <b><i>Conclusions:</i></b> Our results suggest that the detection of <i>MLH1</i> promoter methylation may be a potential prognostic biomarker for GC patients with MSI.

背景与目的：已有研究报道胃癌（gastric cancer，GC）中存在人类mutL同源基因1（Human mutL homolog 1，MLH1）启动子甲基化。本研究旨在探讨MLH1启动子甲基化在胃癌中的临床病理特征、预后价值及诊断效能。方法：本研究计算了合并比值比（odds ratio，OR）、风险比（hazard ratio，HR）及其对应的95%置信区间（95% confidence intervals，95% CI），并对合并灵敏度、特异度及受试者工作特征曲线下面积（area under the curve，AUC）进行了分析。结果：本系统分析共纳入4654例胃癌患者及3669例非恶性对照样本。与胃腺瘤、慢性胃炎、癌旁组织、正常胃黏膜及健康人血液样本相比，胃癌样本中MLH1启动子甲基化水平显著升高；但胃癌样本与肠上皮化生、异型增生样本的甲基化频率无显著差异。MLH1启动子甲基化与患者年龄及微卫星不稳定（microsatellite instability，MSI）存在相关性，但与患者性别、幽门螺杆菌（H. pylori）感染、吸烟饮酒行为、病理组织学类型、肿瘤分化程度、临床分期、淋巴结状态、远处转移及胃癌患者总生存期均无关联。与癌旁组织、胃腺瘤、慢性胃炎、正常胃黏膜及健康人血液样本相比，MLH1启动子甲基化对胃癌患者的诊断灵敏度较低（<0.5）。针对微卫星不稳定型与微卫星稳定（microsatellite stability，MSS）型胃癌样本，MLH1启动子甲基化的合并灵敏度、特异度及AUC分别为0.64、0.96及0.90。结论：本研究结果提示，检测MLH1启动子甲基化或可成为微卫星不稳定型胃癌患者的潜在预后生物标志物。