人口腔鳞状细胞癌和口腔白斑的基因甲基化谱分析

Comparative analysis of methylation profiles in tissues of oral leukoplakia and oral squamous cell carcinoma

目的比较人口腔白斑、口腔鳞状细胞癌（oral squamous cell carcinoma，OSCC）与正常口腔黏膜组织中基因的甲基化变化，以明确DNA甲基化在口腔癌发生发展中的作用。 方法从4例正常口腔黏膜、4例口腔白斑以及4例OSCC组织中提取DNA，样本均来自首都医科大学口腔医学院黏膜科。使用Illumina 450K人全基因组甲基化芯片对其进行检测，对CpG位点发生甲基化改变的相关基因进行基因本体分析（gene ontology，GO）和京都基因和基因组百科全书通路富集分析（Kyoto encyclopedia of genes and genomes，KEGG）。 结果口腔白斑及OSCC组织中基因的CpG位点甲基化状态发生了改变。在口腔白斑中，异常CpG位点中的高甲基化改变达86.18%（23 290/27 025）；低甲基化改变占13.82%（3 734/27 025）。与口腔白斑相比，OSCC无论是高甲基化还是低甲基化的CpG位点均显著增加。多数发生甲基化改变的CpG位点位于CpG岛的外围，其中大约有1/4位于CpG岛滩（距CpG岛0~2 kb），该部位对于基因调控以及肿瘤的发生至关重要。通路分析表明口腔白斑和OSCC组织中发生甲基化改变的CpG位点有共同的通路富集，其中大部分通路都与肿瘤的发生和进展有关。 结论口腔白斑和OSCC在通路方面及基因中都有相似的甲基化改变，表明在口腔白斑和OSCC的发病过程中，它们的表观遗传学方面可能有类似的分子基础。

ObjectiveTo compare the methylation profiles in tissues of oral leukoplakia （OLK） and oral squamous cell carcinoma （OSCC） with healthy tissues of oral mucosa, in order to identify the role of DNA methylation played in tumorigenesis. MethodsDNA samples extracted from tissues of 4 healthy oral mucosa, 4 OSCC and 4 OLK collected from patients of the Department of Oral Medicine, Capital Medical University School of Stomatology were examined and compared using Methylation 450 Bead Chip. The genes associated with differentially methylated CpG sites were selected for gene ontology （GO） analysis and Kyoto encyclopedia of genes and genomes （KEGG） pathway enrichment. ResultsMultiple differentially methylated CpG sites were identified by using the above mentioned assay. Hypermethylation constitutes 86.18% （23 290/27 025） of methylation changes in OLK and hypomethylation accounts for 13.82% （3 734/27 025） of methylation changes. Both hypermethylated and hypomethylated CpG sites were markedly increased in OSCC tissue compared with OLK tissue. The majority of differentially methylated CpG sites were located outside CpG islands, with approximately one-fourth in CpG shores flanking the islands, which were considered highly important for gene regulation and tumorigenesis. Pathway analysis revealed that differentially methylated CpG sites in both OLK and OSCC patients shared the same pathway enrichments, most of which were correlated with carcinogenesis and cancer progression （e.g., DNA repair, cell cycle, and apoptosis）. ConclusionsIn the present study, methylation-associated alterations affect almost all pathways in the cellular network in both OLK and OSCC. OLK and OSCC shared similar methylation changes whether in pathways or genes, indicating that epigenetically they might have the same molecular basis for disease progression.