Vitamin D3 Metabolism and Colorectal Cancer: Correlating Phenotype to Genotype

描述(由申请人提供)： 代谢在人类结直肠癌维生素D3缺乏和对维生素D3治疗的不同反应的发病机制中的作用尚不确定。维生素D3是通过CYP-P450催化的羟基化反应代谢的。维生素D3羟基化酶的三个可能的定量指标是：25-D3/D3比率‘一种衡量CYP27A1和CYP2R1催化的D3到25-D3的羟化的指标；1，25-D3/25-D3的比率’一种衡量CYP27B1催化的25-D3到1，25-D3的羟基化的指标；和24，25-D3/25-D3的比率‘一种主要由CYP24A1催化的25-D3到24，25-D3的羟基化的指标。我们的初步研究显示，在30例维生素D3缺乏的结直肠癌患者中，第90天与基线25-D3/D3比率(p&lt；0.0001)和1，25-D3/25-D3比率(p=0.0241)之间有显著变化。此外，对维生素D3代谢关键基因(DBP、VDR、细胞色素P27A1、细胞色素P27B1和细胞色素P24A1)的74个标签SNP进行的基因分型研究表明，DBP基因中非同义编码SNP的rs4588多态与血清25-D3水平显著相关(1=0.0001)。因此，我们假设维生素D3生物转化相关基因中的功能相关多态(SNPs)可能在个体的维生素D3状态中起作用，这些SNPs可能解释了对补充维生素D3的不同反应。这一假设将在下面的两个特定目标中进行验证，使用来自两个结直肠癌患者队列的血液样本(结直肠癌患者的非干预和胆钙化醇干预)。目的1a)：测定282例非干预者和50例干预者的维生素D3基础状态(激活和失活酶羟化)1b)：测定干预对50例患者3个月时维生素D3状态和羟化表型的影响。这一特定目的的终点指标是：(I)总血清25-D3；24，25-D3和1，25-D3水平；(Ii)血清25-D3/D3；1，25-D3/25-D3和24，25-D3/25-D3比率，与仅血清25-D3的标准指标相比。(Iii)25-D3、24、25-D3和1，25-D3水平的自由血清指数(作为每种维生素D3代谢物的自由指数-定义为血清总代谢物/DBP的摩尔比)。目的：利用282例非干预性结直肠癌患者和50例补充胆钙素的结直肠癌患者外周血中提取的基因组DNA，对调节维生素D3代谢的5个关键基因(DBP、VDR、CYP27A1、CYP27B1和CYP24A1)中74个TagSNPs进行基因分型。基因分型数据将被用来评估Tag SNPs、基线维生素D3状态/羟化表型和人口统计学协变量之间的相关性，这些变量包括：(A)282名CRC患者的非干预队列和(B)50名CRC患者的干预队列(补充胆钙素前后)。如果成功，这项提议可能有助于部分解释导致维生素D3缺乏的变异。这项研究也可以作为预测以维生素D3为基础的干预措施效果的范例。 公共卫生相关性： 维生素D缺乏及其与癌症和其他慢性疾病的关系是一个重要的、日益严重的公共卫生问题。在这项建议中，我们试图找到血液中维生素D代谢产物的模式和与维生素D缺乏相关的维生素D代谢基因的遗传变化。从这项研究中获得的信息可以用来识别与维生素D3缺乏相关的疾病的高危人群，并预测对维生素D治疗的反应。

DESCRIPTION (provided by applicant): The role of metabolism in the pathogenesis of vitamin D3 deficiency and variable responses to vitamin D3 treatment in human colorectal cancer is yet uncertain. Vitamin D3 is metabolized via CYP-P450 catalyzed hydroxylation reactions. The three potential quantitative measures of vitamin D3 hydroxylating enzymes are: 25-D3/D3 ratio ` a measure of CYP27A1 and CYP2R1 catalyzed hydroxylation of D3 to 25-D3; 1,25-D3/25-D3 ratio `a measure of CYP27B1 catalyzed hydroxylation of 25-D3 to 1,25-D3; and 24,25-D3/25-D3 ratio ` a measure of the predominantly CYP24A1 catalyzed hydroxylation of 25-D3 to 24,25-D3. Our preliminary studies showed significant changes between day 90 and baseline 25-D3/D3 ratio (p<0.0001) and 1,25-D3 /25-D3 ratio (p= 0.0241) in 30 vitamin D3 deficient colorectal cancer (CRC) patients. Furthermore, genotyping studies of the 74 tagSNPs in the key vitamin D3 metabolism genes (DBP, VDR, CYP27A1, CYP27B1 and CYP24A1) revealed a significant association between rs4588 polymorphism, a non-synonymous coding SNP in the DBP gene and serum 25-D3 levels (1 =0.0001). Therefore, we hypothesize that functionally relevant polymorphisms (SNPs) in genes involved in Vitamin D3 biotransformation may play a role in an individual's vitamin D3 status and that these SNPs may explain variable response to Vitamin D3 supplementation. This hypothesis will be tested in the two specific aims below using blood samples from two CRC patient cohorts (non intervention and cholecalciferol intervention of colorectal cancer patients). Aim 1a): determine the baseline vitamin D3 status (activating and inactivating enzyme hydroxylation) in 282 non- intervention and 50 intervention patients 1b): determine the effect of intervention with 2000 IU daily oral cholecalciferol supplementation on vitamin D3 status and hydroxylation phenotypes at the 3 month time point for the 50 patients. The endpoint measures for this specific aim are: (i) Total serum 25-D3; 24,25-D3 and 1,25- D3 levels (ii) serum 25-D3/D3; 1,25-D3/25-D3 and 24,25-D3/25-D3 ratios, compared to the standard measure of serum 25-D3 only. (iii) Free serum index of 25-D3, 24,25-D3 and 1,25-D3 levels (measured as free index of each vitamin D3 metabolite---defined as the molar ratio of the total serum metabolite/DBP). Aim 2: Genotype for 74 tagSNPs identified in the five key genes (DBP, VDR, CYP27A1, CYP27B1 and CYP24A1) that regulate vitamin D3 metabolism, using genomic DNA isolated from blood samples of all 282 non- intervention and 50 cholecalciferol supplemented CRC patients. The genotyping data will be used to evaluate the correlation between the tagSNPs, baseline vitamin D3 status/hydroxylation phenotypes and demographic covariates for (a) non-intervention cohort of 282 CRC patients and (b) an intervention cohort of 50 CRC patients (before and after cholecalciferol supplementation). If successful, this proposal may help to explain in part the variations that lead to vitamin D3 deficiency. The study may also serve as a paradigm to predict the efficacy of vitamin D3-based interventions. PUBLIC HEALTH RELEVANCE: Vitamin D deficiency and its relationship to cancer and other chronic diseases is an important and growing public health problem. In this proposal we seek to find blood vitamin Dmetabolite patterns and inherited changes in the vitamin D metabolism genes related to vitamin D deficiency. The information derived from this study could be used to identify individuals at high risk of developing diseases associated with vitamin D3 deficiency and to also predict responses to vitamin D treatment.