Familial Comparative Study Of Inflammatory Cytokine Gene Polymorphisms And Gastric Cancer Susceptibility

ObjectiveGastric cancer is a common malignant tumor of digestive tract.The mechanism of tumorigenesis is not clear yet.Most of scholars have the consensus that the carcinogenesis of gastric cancer is due to the cooperate effect of biologic factors (helicobacter pylori infection),genetic factors and environmental factors(such as dietetic factors,drinking water factors and intake of vitamins).After H.pylori was recognized as a classⅠcarcinogen by WHO in 1994,many researches about the mechanism of H.pylori to gastric tumorigenesis found that H.pylori infection for chronic gastritis is a key factor to induce the gastric cancer.In recent years,some researches indicate that inflammatory cytokines play an important modulatory role in the continuence and development of inflammation and gastric tumorigenesis,and are associated with genetic factors of gastric cancer.According to El-Omar,in the chronic gastritis due to H.pylori infection,pro-inflammatory cytokines include TNF-α,IL-1β,IL-8,IL-12 and IFN-γ,etc;anti-inflammatory cytokines such as IL-4/IL-13,IL-1ra,TGF-βand IL-10,etc.All of them can regulate the inflammation, and then promote or hold back the tumorigenesis.Since El-Omar reported IL-1 polymorphisms had association with the susceptibility of gastric cancer,there are more and more researches suggested that the association of IL-1 polymorphisms and gastric cancer was not coherent among different race and people.Tumor necrosis factor(TNF)-αpolymorphism has association with susceptibility of many diseases, such as coronary heart disease,occupational strain,rheumatoid diseases,but it is seldom reported about the association with gastric cancer.It is rarely seen about the family aggregation of gastric cancer and the change of gastric cancer susceptibility along with the relativeship decreasing through ancestry study.The association research about IL-1B,TNF-A and the genetic susceptibility of gastric cancer is helpful to discover the mechanism of gastric cancer in high prevalence of Henan province,it can make a exact molecular diagnose,screen on the groups with high risks,further provide prognostic analysis possibly.By the case-control familial comparative study,this topic researched on the distribution of polymorphisms of pro-inflammatory cytokines gene IL-1β,TNF-αand anti- inflammatory cytokines IL-1ra in the case's family groups and control's, and the interactive effect between them and H.pylori infection;and ascertained their genetic effect in gastric neoplasia,then probed into and confirmed the association between inflammatory cytokines and the susceptibility of gastric cancer.MethodsTraditional case-control study of epidemiology was combined with familial comparative study in this study.Four villages were sampled by cluster sampling from two counties,Xinxiang County and Xin'an County,which have high prevalence of gastric cancer in Henan province,and then every inhabitant was interviewed for the occurrence of gastric cancer in their families.296 members from cases' families and 319 from controls' families were obtained,and their venous blood samples were collected and stored in -80℃for use.Genome DNA was extracted from the venous blood of all subjects;the polymorphisms genotype were detected by using the polymerase chain reaction-restriction fragment length polymorphisms(PCR-RFLP) and the polymerase chain reaction(PCR),then the products of IL-1B-511,-31,IL-1RN and TNF-A were electrophoresed on 2.0%agarose gels or 8.0%polyacrylamide gel.The associations about H.pylori infection and polymorphisms of IL-1B at positions-31, -511,TNF-A at -308 locus and IL-1RN VNTR[variable numbers of tandem repeats] polymorphism were tested;and the H.pylori infection through ELISA was examined.Results1.In this study,IL-1B-511C/T and T/T genotype,IL-1RN L/*2 and *2/*2, TNF-A-308G/A and A/A genotype were associated with increased risk of non-cardiac adenocarcinoma of stomach[to IL-1B-511T allele,the odds ratio(OR)=2.84,95% confidence interval(95%CI):2.02～4.00,and to IL-1RN*2,OR=3.08,95%CI: 2.11～4.50,to TNF-A-308A allele,OR=3.15,95%CI:2.23～4.40].In the first degree relatives,comparing the cases family with controls family members,the OR values of IL-1B-511T,IL-1RN*2 and TNF-A-308A were 3.60(95%CI:2.68～5.71), 3.26(95%CI:1.80～5.90) and 3.77(95%CI:2.40～5.91) separately;the association strength reduced along with the relative degree decreasing.The positive H.pylori status could increase the risks of IL-1B to gastric cancer and the risk reduced along with the relative degree decreasing,the OR value was 1.79(95%CI:1.19～2.69) in the first degree and 1.10(95%CI:0.58～2.08) in the second degree.2.The logistic regression analysis about the four polymorphisms and H.pylori infection suggested that the polymorphisms and the H.pylori had a synergic effect to the risk of gastric cancer.The OR value of IL-1B-511T allele carriers was 8.26(95%CI:4.16～15.42),the OR value of IL-1RN *2/*2 carriers was 14.19(95%CI: 3.11～26.34),the OR value of TNF-A-308A/A genotype carriers was 8.38(95%CI: 2.24～13.28),and the OR value of H.pylori positive was 5.57(95%CI:3.39～8.84).3.No difference was found in the frequency distribution of IL-1B-31 genotype between the case and control families.But from the haplotype analysis of IL-1B-511, IL-1B-31 and IL-1RN,the CC*L haplotype was taken as reference,the haplotype of CT*L was a protecting factor,its OR value was 0.59(95%CI:0.40～0.88) and as risk factors,the haplotypes of CC*2,CT*2,TC*2 and TT*2 could enhance the risks of gastric cancer,OR values for CC*2,CT*2,TC*2 and TT*2 were 3.73(95%CI: 1.68～8.25),3.14(95%CI:1.73～5.70),2.58(95%CI:1.42～4.71) and 5.27(95%CI: 2.78～9.97).4.The combination analysis of IL-1B-511 and IL-1B-31 genotypes suggested that combined genotypes of CT/CC,CT/CT,CT/TT,TT/CC,TT/CT and TT/TT had the OR values of 5.64(95%CI:2.87～11.06),4.51(95%CI:1.89～10.78),2.80(95%CI: 1.54～5.09),2.08(95%CI:1.27～3.41),2.08(95%CI:1.08～3.99) and 5.71(95%CI: 2.95～11.02).ConclusionsThe variant genotypes of IL-1B-511T,TNF-A-308A and IL-1RN*2 are the risks of gastric cancer,and they have synergic effects with H.pylori infection;the infection of H.pylori affected by genetic factor is a risk factor to gastric cancer;the association strength reduced along with the relative degree decreasing.The haplotype analysis of IL-1B-511,IL-1B-31 and IL-1RN polymorphisms suggested that the haplotype of CT*L was a protecting factor and the haplotypes of TT*2, CT*2,TC*2 and CC*2 could enhance the risks of gastric cancer could enhance the risks of gastric cancer.The combined genotypes of CT/CC,CT/CT,CT/TT,TT/CC, TT/CT and TT/TT could increase the risk of gastric cancer comparing with the separate genotypes.