Methylation and mutations in RB1 and variants of synthetic folic acid metabolism

RB1 的甲基化和突变以及合成叶酸代谢的变异

基本信息

批准号：
9139422
负责人：
Manuela A Orjuela
金额：
$ 51.51万
依托单位：
COLUMBIA UNIVERSITY HEALTH SCIENCES
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-09-07 至 2018-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9139422
关键词：
Adult Affect Age Alleles Biological Biological Assay Case Series Cells Child Childhood Colon Carcinoma Colonic Adenoma CpG Islands Cytosine DNA Data Deamination Defect Development Diet Dietary intake Dihydrofolate Reductase Disease Environmental Exposure Epidemiologic Studies Evaluation Fetal Development First Pregnancy Trimester Folic Acid Food Supplements Fortified Food Frequencies Genes Genetic Polymorphism Genetic Variation Genotype Glioblastoma Handedness Health Health Policy Hereditary Retinoblastoma Homozygote Human Hypermethylation Incidence Ingestion Intake Lead Leukocytes Lung Malignant - descriptor Malignant Childhood Neoplasm Malignant Neoplasms Malignant neoplasm of lung Measures Methylation Mexico Modeling Mothers Mutation Newly Diagnosed Nonsense Codon Nutrient Persons Plasma Predisposition Pregnancy Pregnancy Trimesters Promoter Regions Prospective Studies Prostate Public Health RB1 gene Retina Retinal Retinoblastoma Retinoblastoma Protein Risk Sampling Site Testing Variant Woman Work base carcinogenesis cohort disease-causing mutation early childhood epigenome folic acid metabolism folic acid supplementation high risk in utero lung small cell carcinoma malignant breast neoplasm mouse model neurodevelopment outcome forecast prenatal promoter pyrosequencing response tumor tumor DNA tumor progression

项目摘要

DESCRIPTION (provided by applicant): Synthetic folic acid supplements are consumed by 50% of US adults. High folic acid intake can result in CpG island hypermethylation. Recent studies suggest high intake may contribute to carcinogenesis particularly in those persons unable to metabolize folic acid efficiently such as persons homozygous for the 19bp deletion polymorphism in the dihydrofolate reductase(DHFR) gene (rs70991108). Homozygotes (19% of US adults) have less efficient conversion of synthetic folic acid into biological folate. Women homozygous for the DHFR19bp deletion (DHFR19bpdel) are at increased risk for having a child with retinoblastoma, a neuro-ectodermally derived early childhood cancer that has served as a model for understanding carcinogenesis. This risk appears elevated among women homozygous for DHFR19bpdel who consumed folic acid containing prenatal supplements in the first trimester. In retinoblastoma, 37% of disease-causing mutations in the CpG-rich gene, RB1, are due to deamination of methylated cytosines in RB1, while an additional 12% are caused by methylation of the RB1 promoter. We hypothesize that these methylation related RB1-inactivating changes may be induced by less functional genetic variations in folate metabolism and excess exposure in early retinal development. Murine models suggest particular sensitivity to folic acid exposure in early neural development. In humans, periods of dietary inadequacy in early gestation are associated with hyper-methylation at meta- stable epialleles. Pilot data from mutation assays and methylation arrays from our ongoing case-series study of newly diagnosed retinoblastoma (mean age 23 months) in Central Mexico, EpiRbMx, suggest that women who have the less efficient DHFR 19bpdel and high folic acid prenatally have higher risk of a child with a methylation related RB1-inactivating mutation or differentially hyper-methylated RB1 promoter directly resulting in tumor formation. Maternal DHFR19bpdel homozygosity combined with high prenatal folic acid intake may lead to RB1 hyper-methylation in developmentally susceptible cells, thereby contributing to carcinogenesis. Based on the results of our pilot data, we propose to use existing samples and data from 337 cases in our ongoing EpiRbMx study (founded in 2003) including pre-treatment measures of mother and child plasma nutrients, diet intake, genotype, and tumors, to test our hypothesis of an association between maternal DHFR 19bpdel and prenatal folic acid exposure (using plasma and intake measures) and 1) methylation related RB1 mutations, specifically in somatic (non-germline) RB1 mutations, and 2) methylation of the RB1 promoter. We will further examine the impact of DHFR and prenatal folic acid exposure on differential methylation in metastable epialleles to document their effect on the developing epigenome. Given the high frequency of RB1 mutations among poor prognosis adult tumors such as small cell lung cancer(54%) or glioblastoma(11%) and the high proportion (19%) of adults with less efficient folic acid metabolism, the potential translational impact of our study is high, as our results can inform public health policy and evaluation of synthetic folic acid exposure.

描述（由申请人提供）：50% 的美国成年人食用合成叶酸补充剂。高叶酸摄入量可能导致 CpG 岛过度甲基化，特别是对于那些无法有效代谢叶酸的人。例如二氢叶酸还原酶（DHFR）基因（rs70991108）中19bp缺失多态性纯合的人。纯合子（19% 的美国成年人）将合成叶酸转化为生物叶酸的效率较低。DHFR19bp 缺失 (DHFR19bpdel) 纯合子的女性患视网膜母细胞瘤的风险增加，视网膜母细胞瘤是一种神经外胚层衍生的早期儿童癌症。作为了解致癌作用的模型，在首次食用含叶酸的产前补充剂的 DHFR19bpdel 纯合子女性中，这种风险似乎升高。在视网膜母细胞瘤中，富含 CpG 的基因 RB1 中 37% 的致病突变是由于 RB1 中甲基化胞嘧啶的脱氨基作用造成的，而另外 12% 则是由 RB1 启动子的甲基化引起的。相关的 RB1 失活变化可能是由叶酸代谢功能性遗传变异较少和早期视网膜发育中的过量暴露引起的，这表明对叶酸特别敏感。在人类中，妊娠早期饮食不足与亚稳定表观等位基因的过度甲基化有关，这些数据来自我们正在进行的新诊断视网膜母细胞瘤病例系列研究的突变测定和甲基化阵列。墨西哥中部的 EpiRbMx（23 个月大）表明，产前 DHFR 19bpdel 效率较低且叶酸含量较高的女性生下患有以下疾病的孩子的风险较高：甲基化相关的RB1失活突变或差异性高甲基化RB1启动子直接导致母体DHFR19bpdel纯合性加上产前高叶酸摄入可能导致发育易感细胞中的RB1高甲基化，从而促进致癌。根据我们的试点数据，我们建议在我们正在进行的 EpiRbMx 研究（成立于 2003 年）中使用来自 337 个病例的现有样本和数据，包括母亲和儿童血浆营养素、饮食摄入量、基因型和肿瘤的治疗前测量，以检验我们关于母体 DHFR 19bpdel 与产前叶酸暴露（使用血浆和摄入量测量）之间关联的假设，以及 1) 甲基化相关的 RB1 突变，特别是在体细胞（非种系）RB1 突变中，以及 2) RB1 启动子的甲基化中，我们将进一步研究 DHFR 和产前叶酸暴露对差异甲基化的影响。亚稳态表观等位基因来记录它们鉴于小细胞肺癌 (54%) 或胶质母细胞瘤 (11%) 等预后不良的成人肿瘤中 RB1 突变的频率较高，以及叶酸代谢效率较低的成人比例较高 (19%)。，我们研究的潜在转化影响很高，因为我们的结果可以为公共卫生政策和合成叶酸暴露的评估提供信息。