Vitamin D3 Metabolism and Colorectal Cancer: Correlating Phenotype to Genotype

描述（由申请人提供）： 代谢在维生素D3缺乏的发病机制中的作用以及对人类结直肠癌中维生素D3治疗的可变反应尚不确定。维生素D3通过CYP-P450催化的羟基化反应代谢。维生素D3羟化酶的三种潜在定量指标是：25-D3/D3比率"衡量CYP 27 A1和CYP 2 R1催化的D3羟化为25-D3; 1，25-D3/25-D3比率“衡量CYP 27 B1催化的25-D3羟化为1，25-D3;和24，25-D3/25-D3比率“是主要由CYP 24 A1催化的25-D3羟基化为24，25-D3的量度。我们的初步研究显示，在30名维生素D3缺乏的结直肠癌（CRC）患者中，第90天与基线25-D3/D3比值（p<0.0001）和1，25-D3 /25-D3比值（p= 0.0241）之间存在显著变化。此外，对关键维生素D3代谢基因（DBP、VDR、CYP 27 A1、CYP 27 B1和CYP 24 A1）中的74个tagSNPs进行的基因分型研究显示，DBP基因中的非同义编码SNP rs 4588多态性与血清25-D3水平之间存在显著相关性（1 =0.0001）。因此，我们假设参与维生素D3生物转化的基因中的功能相关多态性（SNPs）可能在个体的维生素D3状态中发挥作用，并且这些SNPs可能解释对维生素D3补充剂的可变反应。将使用来自两个CRC患者队列（结直肠癌患者的非干预和胆钙化醇干预）的血液样本在以下两个特定目的中检验该假设。目标1a）：确定282名非干预患者和50名干预患者的基线维生素D3状态（激活和失活酶羟基化）1b）：确定在3个月时间点，50名患者每日口服补充2000 IU胆钙化醇干预对维生素D3状态和羟基化表型的影响。该特定目标的终点测量是：（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的标准测量相比。(iii)25-D3、24，25-D3和1，25-D3水平的游离血清指数（测量为每种维生素D3代谢物的游离指数-定义为总血清代谢物/DBP的摩尔比）。目标二：使用从所有282名非干预和50名补充胆钙化醇的CRC患者的血液样本中分离的基因组DNA，在调节维生素D3代谢的5个关键基因（DBP、VDR、CYP 27 A1、CYP 27 B1和CYP 24 A1）中鉴定74个tagSNP的基因型。基因分型数据将用于评价（a）282例CRC患者的非干预队列和（B）50例CRC患者的干预队列（补充胆钙化醇前后）的tagSNP、基线维生素D3状态/羟基化表型和人口统计学协变量之间的相关性。如果成功的话，这一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一个范例，预测基于维生素D3的干预措施的疗效。 公共卫生相关性： 维生素D缺乏症及其与癌症和其他慢性疾病的关系是一个重要的和日益严重的公共卫生问题。在这个建议中，我们试图找到血液维生素D代谢模式和维生素D代谢基因的遗传变化与维生素D缺乏症。从这项研究中获得的信息可用于识别患有与维生素D3缺乏相关疾病的高风险个体，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.