Global DNA methylation and genetic factors associated with folate metabolism on carcinogenesis in pancreatic cancer.

本研究旨在阐明癌症整体DNA低甲基化特征与叶酸代谢途径中最明显的MTRR和MTHFR遗传多态性之间的关系。为了确定与氨基酸变化相关的遗传多态性的功能活性，我们构建了含有MTHFR和MTRR变异的cDNA。通过测量3H- SAM中甲基的掺入来测定总DNA甲基化。我们发现外源MTHFR蛋白在携带Val222或Ala429的MTHFR转染物中产生的水平低于野生型。相比之下，外源MTRR蛋白在Met22变异体和野生型之间没有明显差异。转染MTHFR后，培养液中的Hcy和DNA甲基化水平均明显低于对照组。结果表明，与叶酸代谢相关的多态性基因通过调节甲基化状态参与致癌。

The study aimed to elucidate the relationship between global DNA hypomethylation characteristics of cancer and genetic polymorphisms of MTRR and MTHFR which are most evident in the folate metabolic pathway. To determine the functional activities in genetic polymorphisms associated with an amino acid change, we constructed cDNA with variation of MTHFR and MTRR. Total DNA methylation was determined by measuring the incorporation of methyl groups from 3H- SAM. We found that the exogenous MTHFR protein was produced at lower levels in the MTHFR transfectants harboring Val222 or Ala429 than in the wild-type. In contrast, exogenous MTRR protein showed no obvious differences between the Met22 variants and wild-type. MTHFR transfectants showed markedly decreased Hcy in culture media and a lower level of DNA methylation than did the control. The results indicate that polymorphic genes related to folate metabolism are involved in carcinogenesis through modulation of the methylation status.