A Study On The Association Between Polymorphisms Of UGT1A7 And Susceptibility Of Hepatocellular Carcinoma In Northeast China

IntroductionHepatocellular carcinoma (HCC) is one of the most common malignancies and the third cause of death from cancer in the world. The situation in China is even worse, for about 55% of the world new HCC cases come from China and the incidence rate of HCC in China is increasing.Chronic infection with either hepatitis B virus (HBV) or hepatitis C virus (HCV), dietary aflatoxin exposure and alcohol consumption are important risk factors for HCC. However, only a minority of people at risk eventually develops HCC and it is likely that there may be some modified mechanisms involved during the development of HCC.The human uridine 5'-diphosphate (UDP)-glucuronosyltransferases (UGTs) are an enzyme superfamily that catalyzes the glucuronidation of both endogenous compounds such as bilirubin and steroid hormones, as well as exogenous compounds such as environmental carcinogens (including polycyclic aromatic hydrocarbons and heterocyclic amines) and dietary constituents. The UGT1A7 is one of the products by alternative splicing of exon one to the four common exons(exon2-exon5) of UGT1A gene and it metabolizes a variety of clinically and toxicologically important compounds such as benzo(a)pyrene. So far, several missense variants of UGT1A7 have been discovered and polymorphisms of UGT1A7 could alter the enzymatic activity of the encoded protein and have been reported to be involved in colorectal cancer, lung cancer, breast cancer and pancreatic cancer. Several studies have suggest a link between polymorphisms of UGT1A7 and HCC susceptivity. However, the role of the UGT1A7 still need further study as other studies gained controversial conclusions.In this study, we detected the genetic polymorphisms of UGT1A7 gene in a group of hospital-derived HCC patients and their age and gender frequency-matched controls, which all came from Northeast China.Materials and methodsThis study was a hospital-based, case-control study under an established protocolBlood samples were collected from consecutive HCC patients hospitalizing for the first time in a hospital from October,2007 to April,2008. Once recruiting HCC patients, we selected a group of age(±5) and sex frequency-matched controls without cancer and liver diseases in the same hospital who attended the physical examination center. All subjects were investigated with a questionnaire including demographic characteristics, history of disease, consumption of tobacco and alcohol, family history of HCC and other tumors by trained investigators. Blood samples were collected in EDTA tubes and stored at-20℃until DNA extraction. Genome DNA was isolated by potassium iodide technique.For UGT1A7, we screened the mutations in codons 129,131 and 208 using polymerase chain reaction (PCR)-based genotyping techniques including allele-specific PCR (AS-PCR) and PCR-restriction fragment length polymorphism (RFLP). Firstly, sequences of UGT1A7 containing codons 129/131 and 208 were amplified. Secondly, allele-specific PCR were applied to determine the sequence variants at codons 129 and 131. Two independent parallel amplifications were performed with different forward primers but the same reverse primer using the 2000-fold-diluted product of the fist PCR as template. Finally, the second PCR products were digested with the restriction enzyme Rsa I to detect polymorphism of codon 208. ResultThe UGT1A7*1/*2 and *3/*3 genotypes were associated with higher HCC risk (OR 2.1,95%CI 1.10-3.97; OR 5.7,95%CI 1.76-18.30, respectively). The proportion of UGT1A7 low enzymatic allele (UGT1A7*2 or UGT1A7*3) was higher in HCC patients than those in controls, and there was an linear trend between the number of mutation site and risk of HCC. Interaction analysis indicated that individuals with both risk categotied genotype and infection of HBV or HCV had higher risk of HCC than those with only one of them. In addition to polymorphisms of UGT1A7, multivariate logistic regression analysis demonstrated other significant independent factors associated with HCC were HBV infection, HCV infection,history of cirrhosis and family history of HCC.ConclusionOur study showed that the polymorphisms of UGT1A7 are associated with higher HCC risk.There were synergism effect of polymorphisms of UGT1A7 and infection with HBV or HCV on risk of hepatocellular carcinoma.