Single Nucleotide Polymorphism In Sex Hormone-binding Globulin And IL-6Genes And The Incidence Of Hepatocellular Carcinoma

BackgroundIn recent years, incidence rate of hepatocellular carcinoma (HCC) is increasing every year. HCC has become one of important disease burden in some regions, especially in Asia and sub-Saharan Africa. The incidence of HCC ranks fifth for cancers worldwide and causes about half a million deaths every year. China is the main high incidence region for primary liver cancer and there are50%of HCC patients from China throughout the whole world. Guangxi is one of the high risk regions of HCC in China. In Guangxi, during the2004-2005interval, liver cancer is first leading cause of cancer related, which accounted for30.70%. HCC’s prevalence can harm people’s health and life seriously. It is most important to prevention and control of HCC. Etiology research is the key for establishing the prevention and control measures.Single nucleotide polymorphism (SNP) is the third generation of genetic marker, which is often used as a genetic susceptibility marker of complex diseases, especially in cancer. We can found out the predisposition genes by the gene-SNP-disease association study, which can provide genetics evidence for molecular mechanism related to tumorigenesis. Gender disparity of HCC indicates the sex hormone may play a key role in the etiology of HCC. Sex hormone regulation involves many factors, including the factors relating to synthesis, metabolism and transport, such as metabolism enzyme, receptor and binding protein. It is vital valuable to investigate the relationship between those regulators and HCC. Previous studies shows that polymorphisms in the genes related to sex hormones metabolic enzymes and receptors may be associated with risk of HCC. However, to the best of our knowledge, the relationship between polymorphism of sex hormone-binding globulin gene (SHBG) and risk of HCC has not been reported. IL-6is a multi-functional cytokines responding to liver virus infection and inflammation. The risen of IL-6expression lever can promote the development of HCC, which may be regulated by gender factor. It was reported that polymorphisms of IL-6may not be associated with HCC susceptibility in previous case-control studies, of which both the two genders were recruited in the case group and the results may be affected by gender confounding.This study preliminary investigated the relationship between the polymorphism of SHBG gene and incidence of HCC through a hospital-based case-control study. In addition, we also detected the association between polymorphism of IL-6and susceptibility of HCC along in men in order to control the effect of gender factor. This study aimed to find the relationship between the two factors and HCC and provide the evidence for the etiology research of HCC in genetics. Part1Association of Single Nucleotide Polymorphism of Sex Hormone-binding Globulin Gene and Incidence of Hepatocellular CarcinomaObjectivesTo investigate the association between polymorphism of sex hormone-binding globulin gene (SHBG) and the incidence of hepatocellular carcinoma (HCC). We also detect the gene interaction with HCC risk factors such as smoking, drinking, and chronic HBV infections and compare the age of onset of different genotypes among the HCC patients. This study aims to provide a new way to clarify the relationship between sex hormone and HCC incidence and new direction for prevention and treatment of HCC.MethodsThe research was designed as a hospital-based case-control study. From June2007to October2008,621newly clinical or pathology diagnosed HCC patients from the First Affiliated Hospital of Guangxi Medical University and the Tumor Hospital of Guangxi were enrolled as the case group. At the same time,621cases of non-cancer patients, from the Spinal Orthopedic Department and Traumatic Department of the First Affiliated Hospital of Guangxi Medical University, were enrolled as the control group, which were frequency matched with the case by ages, sex, and ethnic. All participants agreed to participate in and had signed the study consensus protocol. All subjects were surveyed face to face by the specifically trained investigators. The features of questionaire included demographic data, disease history, personal history, family history, smoking history, drinking history, eating habits and way of life etc.2ml fasting venous blood were collected at the second day morning, and genome DNA were extracted at the same day. A SNP loci of SHBG genes, at rs6259(Asp327Asn), was selected by the SNPinfo platform (http://snpinfo.niehs.nih.gov/) and SNP was measured with high flux TaqMan MGB, a fluorescent quantitative real time PCR method. All data were input and analyzed statistically in SPSS13.0for Windows. Categorical data were compared with the chi-square test or Fisher’s exact text. Shesis software was applied to test Hardy-Weinberg genetic balance. The association of gene-disease and interaction of the related factor were analyzed with the non-conditional logistic regress model. And the relative risk scale was measured by odd ratio and95%confidence interval indicated. The Kaplan-Meier survival analysis was used to detect the relationship between onset age of HCC and genotypes. The onset age of different genotypes was compared by Log-rank text. All statistical tests were two-sided with a=0.05.Results1. There were no statistically differences in the distributions of gender, age and ethnic but smoking history, drinking history, HBV infection, HCC family history and history of eating fish raw between cases and controls.2. In the control group, the distribution of genotypes accorded with Hardy-Weinberg genetic balance law (x2=2.18, P=0.14), which indicated the population representative of the controls. The allele frequencies of Asp and Asn were92.51%and7.49%in the case group while89.69%and10.31%in the control group. The difference was statistically significant (x2=55.15,P<0.01). The genotype frequencies of Asp/Asp, Asp/Asn and Asn/Asn were86.31%, 12.40%and1.29%in the case group while81.00%,17.39%and1.61%in the control group. The difference was statistically significant too (x2=6.465, P=0.04).3. Compared with the individual harboring Asp/Asp genotype, the Asp/Asn and Asn/Asn genotypes were not associated with the risk of HCC. However, the combined genotype Asn/Asn+Asp/Asn was associated with a reduced risk of HCC when compared with the Asp/Asp genotype (OR=0.63,95%CI:0.40～0.92).4. Interaction analysis showed that SHBG gene had interaction with drinking (P<0.05), HBV infection (P<0.05) but not smoking (P=0.22). HCC risk of the Asp/Asp genotype carriers with drinking was increased by3.45folds (95%CI:1.74-6.83) compared with the Asn/Asn+Asp/Asn genotype carriers without drinking. And HCC risk of the Asp/Asp genotype carriers with HBV infection was increased by40.77folds(95%CI:21.60～76.97) compared with the Asn/Asn+Asp/Asn genotype carriers without HBV infection.5. Survival analysis of the onset age of the621HCC patients indicated that the mean age of onset had no statistical difference between Asp/Asp genotype and Asn/Asn+Asp/Asn genotype (x2=2.18, P>0.05). However, stratified analysis showed that the mean age of onset of Asn/Asn+Asp/Asn genotype was almost6years later than that of Asp/Asp genotype(Log-rank test,x2=6.91, P<0.01) among those patients with history of drinking.ConclusionsSHBG-SNP Asp327Asn may be associated with both the HCC risk and age of onset. The polymorphism of the loci had interaction with drinking and HBV infection. Part2Relationship between polymorphisms of-572G/C loci in promoter region of IL-6and Hepatocellular Carcinoma risk in menObjectivesTo investigate the association between SNP of IL-6-572G/C and HCC risk in men.MethodsA hospital-based case-control study was conducted in500male patients with HCC from the First Affiliated Hospital and Affiliated Tumor Hospital of Guangxi Medical University and590cancer-free controls from First Affiliated Hospital of Guangxi Medical University. All the patients were newly clinical or pathology diagnosed with HCC and without tumor history in other organs. The controls were recruited from the Department of Orthopedics and Ophthalmology. SNP of IL-6promoter-572G/C loci were detected by ABI7500real-time fluorescence quantitative PCR. Chi-square test and unconditional logistic regression were applied to analyze risk of HCC among different genotypes carriers and the interaction of gene-environment.ResultsFor frequencies of alleles and genotypes of-572G/C loci, there were no significant differences between cases and controls (p>0.05). However, multivariate logistic regression analysis showed that G allele (CG+GG genotypes) was associated with increase risk of HCC with OR=1.31(95%CI:1.00～1.71) compared with CC genotype. Interaction analysis indicated that polymorphism of IL-6-572G/C loci had interaction with HBV infection (P=0.01) but not smoking (P=0.15) and drinking (P=0.06). HCC risk of the CG+GG genotype carriers with HBV infection was increased by5.95folds (95%CI:3.99-8.87) compared with the CC genotype carriers without HBV infection.ConclusionsPolymorphism of IL-6promoter-572loci may be associated with HCC occurrence in men. There was interaction between the gene polymorphism and HBV infection.