Abstract

DNA hypermethylation and mutations are key mechanisms for the downregulation of tumor suppressor genes. NotI-microarrays allowed us to detect hypermethylation and/or deletions in 180 NotI sites associated with 188 genes of human chromosome 3, in 24 paired (tumor/normal) colon samples. The most frequent aberrations (in more than 20% of tumor samples) were detected in the promoter regions of 20 genes. Expression and promoter methylation of these genes were analyzed using the data for paired colon samples from The Cancer Genome Atlas project. Three genes—ALDH1L1, PLCL2, and PPP2R3A—revealed a more than two-fold average decrease in expression and a negative correlation between mRNA level and promoter hypermethylation. The expression of these three genes was then evaluated in 30 paired colon samples by quantitative PCR. Frequent (in more than 60% of cases) and significant (5–9-fold on average) mRNA level decrease was found for each of the genes in the tumor samples. The results indicate a suppressor role of the ALDH1L1, PLCL2, and PPP2R3A genes in colon cancer, as well as functional significance of hypermethylation in the downregulation of these genes.

中文翻译：

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ALDH1L1，PLCL2和PPP2R3A在结肠癌中的功能性超甲基化

摘要

DNA高甲基化和突变是下调肿瘤抑制基因的关键机制。NotI芯片使我们能够在24对配对的（肿瘤/正常）结肠样本中检测与人类3号染色体188个基因相关的180个NotI位点的超甲基化和/或缺失。在20个基因的启动子区域中检测到最频繁的畸变（在超过20％的肿瘤样本中）。使用来自The Cancer Genome Atlas项目的成对结肠样本数据分析了这些基因的表达和启动子甲基化。三个基因— ALDH1L1，PLCL2和PPP2R3A-揭示了平均两倍以上的表达下降，以及mRNA水平与启动子高甲基化之间的负相关。然后通过定量PCR在30对配对的结肠样品中评估这三个基因的表达。发现肿瘤样品中每个基因的mRNA水平都频繁（超过60％的情况）显着下降（平均5-9倍）。结果表明，ALDH1L1，PLCL2和PPP2R3A基因在结肠癌中具有抑制作用，以及在这些基因的下调中高甲基化的功能意义。