UGT1A8基因多态与结直肠癌的相关性

Polymorphism of UDP-glucuronosyltransferase UGT1A8 gene in human colorectal cancer

目的:探讨葡萄糖醛酸转移酶UGT1A8基因多态与结直肠癌的相关性.方法:结直肠癌病例组与正常对照组各109例,取静脉血5mL,提取DNA,PCR扩增获得UGT1A8第一外显子,对扩增产物检测、纯化及测序.每个基因型样本克隆至TOPOTA质粒,通过DNA序列分析其特性.经双尾Fisher精确检验,确定各等位基因及基因型在病例组与对照组中的分布差异.计算OR值及95%CI,评价研究因素与结直肠癌的相关强度.采用Logistic回归分析UGT1A8各基因型及性别因素对结直肠癌的易感性.结果:UGT1A8基因第一外显子区域存在3个突变位点.野生型UGT1A8*1等位基因频率在对照组高于病例组(P=0.047),两组差异有统计学意义,OR值为0.51(95%CI0.28-0.79),此等位基因为保护性因素.突变型等位基因UGT1A8*3频率在正常对照组稀有,明显低于病例组(P=0.003),OR值为9.63(95%CI2.12-7.79),此等位基因为结直肠癌的危险因子.纯合基因型UGT1A8*1/*1在正常对照组比例高于病例组(P=0.045),OR值为0.28(95%CI0.16-0.88),此基因型的危险度减少.UGT1A8*1/*3杂合基因型(P=0.028)、UGT1A8*2/*3杂合基因型(P=0.003)在病例组高于对照组,OR值分别为5.03(95%CI2.25-5.99)及12.90(95%CI2.68-6.15),这两种基因型为结直肠癌的易感性因素.Logistic回归分析,UGT1A8等位基因多态性是结直肠癌发生的主要影响因素(P=0.029),性别因素影响不明显(P=0.25).结论:结直肠癌UGT1A8呈现明显的基因多态性,野生型UGT1A8*1等位基因为保护性因素,突变型UGT1A8*3为结直肠癌的危险因子.UGT1A8*1/*3、UGT1A8*2/*3杂合基因型为结直肠癌的易感性因素.

AIM： To explore the relationship between the polymorphism of UDP-glucuronosyitransferase UGT1A8 gene and human colorectal cancer （CRC）. METHODS： One hundred and nine cases of colorectal cancer and normal controls （NC）, respectively, were collected for analysis. Genomic DNA was prepared from full blood samples. The amplification of UGT1A8 exon-1 sequences was performed using exon-1 specific primer. And the products were visualized by gel electrophoresis and the fragments were purified. The extracted DNA was subcloned into TOPO TA plasmid and the insert was sequenced for the allelic specificity. Two-tailed Fisher＇s exact test was used to determine the differences of allelic genotypes between CRC and NC group. Odds ratios （ORs） and confidence interval （CI） were calculated to evaluate the relationship between the gene polymorphism and the grades of CRC. The predisposition factors of CRC were analyzed by Logistics. RESULTS： Three mutations were identified in UGT1A8 exon-1. The allele frequency of wild UGT1A8^＊1 was higher in controls when compared with that in CRC （P = 0.047, OR = 0.51,95% CI： 0.28-0.79）, suggesting that this allele was a protective factor. The frequency of mutant UGT1A8^＊3 was significantly lower in controls than that in CRC （P= 0.003, OR= 9.63, 95% CI： 2.12-7.79）, indicating UGT1A8^＊3 as a risk factor of CRC. The expression of homozygous UGTIA8^＊1 was markedly higher in controls than that in CRC （P = 0.045）. Both heterozygous UGT1 A8^＊1/^＊3 and UGT1 A8^＊2/^＊3 were more significantly expressed in CRC as compared with that in controls （P〈0.05, OR= 5.03, 95% CI： 2.25-5.99; P= 0.003, OR= 12.90, 95% CI： 2.68-6.15）. Logistic regression analysis demonstrated that the occurrence of CRC was mainly related to the presence of polymorphic UGT1A8 alleles （P= 0.029）, but not the sex of the patients （P = 0.25）. CONCLUSION： The high incidence of UGT1A8 polymorphism exists in the patients with colorectal cancer. UGT1A8^＊1 allele is a protective factor and UGT1A8^＊3 allele is a risk factor for CRC. Homozygous UGT1A8^＊1/^＊3 and UGT1A8^＊2/^＊3 are also associated with the high occurrence of CRC.