Aspirin, UGT1A6 Genotype, and Colon Gene Expression

描述(申请人提供)：结直肠癌被认为是 一系列分子变化的结果，改变了正常的上皮细胞 细胞转化为结直肠癌，以腺瘤性息肉为中介 在这个过程中迈出一步。降低这种癌症死亡率的一种方法是 使用口服药物以防止肿瘤在大肠中发展。 定期使用阿司匹林和其他非类固醇抗炎药(NSAIDs) 将结肠腺瘤和癌症的发病率降低约 50%。与阿司匹林代谢密切相关的酶有 UDP-葡萄糖醛酸基转移酶(UGT)。UGT1A6是一种多态的UGT及其变体 等位基因代谢阿司匹林的效率较低。我们发现，在非甾体抗炎药的使用者中， 尤其是服用阿司匹林的人，患结肠癌的风险只会降低 在UGT1A6杂合和纯合子变异但不是 纯合子野生型。阿司匹林及其代谢物水杨酸可以抑制 通过抑制环氧合酶(前列腺素的催化剂)生长 合成)，促进细胞凋亡，以及其他尚未确定的途径。 该项目的目标是确定UGT1A6基因对 阿司匹林代谢及阿司匹林诱导的结肠基因表达变化 细胞凋亡的蛋白标记物(Bax和Bcl2)。我们建议研究：1) 380例正常人尿阿司匹林代谢物排泄量的研究 一项横断面研究中的不同UGT1A6基因型别和2)结肠的变化 阿司匹林补充剂诱导的基因表达 40名野生型纯合子个体的安慰剂对照试验 或UGT1A6的纯合子变体。我们假设在缓慢的代谢物中 葡萄糖醛酸化代谢物的比例较小， 阿司匹林剂量的比例是在特定时间内排出的。改建 将使用基因芯片分析确定在结肠中的基因表达 乙状结肠和直肠组织活检RNA及Bax、Bcl2的表达 结肠隐窝将用免疫组织化学方法测量。我们假设 例如，促进生长基因的表达将会减少，并导致细胞凋亡 在使用阿司匹林期间基因增加，这种减少可能在 慢代谢剂比快代谢剂。该项目还将允许 阿司匹林影响表达的其他基因的鉴定 补充。最终，从这个项目中获得的信息将是 有助于开发专门针对通路的化学预防药物 与结肠肿瘤有关。通过针对相关途径、副作用 可以避免使用非甾体抗炎药或特定的COX-2抑制剂。

DESCRIPTION (provided by applicant): Colorectal cancers are thought to arise as the result of a series of molecular changes that transform normal epithelial cells into a colorectal carcinoma, with an adenomatous polyp as an intermediate step in this process. One way to reduce mortality from this cancer involves the use of oral agents that prevent neoplasms from developing in the large bowel. Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) reduces the incidence of colon adenomas as well as carcinomas by approximately 50 percent. Enzymes prominently involved in metabolizing aspirin are UDP-glucuronosyltransferases (UGT). UGT1A6 is a polymorphic UGT and its variant alleles metabolize aspirin less efficiently. We showed that in NSAIDs users, and aspirin users in particular, the risk for colon neoplasia is reduced only in individuals who are UGT1A6 heterozygous and homozygous variant, but not homozygous wild-type. Aspirin and its metabolite, salicylic acid, can inhibit growth through the inhibition of cyclooxygenases (catalysts of prostaglandin synthesis), the promotion of apoptosis, and other as yet unidentified pathways. The goal of this project is to determine the effect of UGT1A6 genotype on aspirin metabolism and on aspirin-induced changes in colonic gene expression and protein markers of apoptosis (Bax and Bcl-2). We propose to study: 1) urinary excretion of aspirin metabolites in 380 healthy individuals with different UGT1A6 genotypes in a cross-sectional study and 2) changes in colon gene expression induced by aspirin supplementation in a randomized, placebo-controlled trial of 40 individuals who are either homozygous wild-type or homozygous variant for UGT1A6. We hypothesize that in slow metabolizers the proportion of glucuronidated metabolites is smaller and that a smaller proportion of the aspirin dose is excreted within a specific time. Alterations in colonic gene expression will be determined using cDNA microarray analysis of biopsy RNA from the sigmoid colon and rectum and Bax and Bcl-2 expression in the colonic crypts will be measured by immunohistochemistry. We hypothesize that expression of e.g. growth-promoting genes will be reduced and apoptotic genes increased during aspirin use and that this reduction may be stronger in slow metabolizers than fast metabolizers. This project will also allow the identification of other genes whose expression is affected by aspirin supplementation. Ultimately, information obtained from this project will be useful in developing chemopreventive drugs that specifically target pathways involved in colon neoplasia. By targeting relevant pathways, side effects caused by the use of NSAIDs or specific Cox-2 inhibitors may be avoided.