Association Between MTORC1Genes Polymorphisms And Genetic Susceptibility Of Hepatocellular Carcinoma

ObjectivesMammalian Target of Rapamycin (mTOR) is a vital signal conductingmolecule that is centrally involved in the regulation of cell growth, proliferation,differentiation and apoptosis by integrating extracellular signals and affectinggene transcription and protein translation. mTORC1is particularly important inthe above aspects of the regulation as one kind of the main complexes of mTOR.mTORC1is composed of mTOR、mLST8、RPTOR. It has been found that theabnormal activity mTOR signaling pathway plays an important role in theformation, development and transfer process of cancer. Some single nucleotidepolymorphisms（SNPs) in mTOR may influence the formation and progressionof tumor by affecting the activity of mTOR pathway. In the current study, weassess the association between the potentially functional8SNPs (rs2536(T>C)and rs1883965(G>A) in mTOR gene, rs3160(T>C) and rs26865(A>G) inmLST8gene, rs1062935(T>C), rs3751932(T>C), rs3751934(C>A) andrs12602885(G>A) in RPTOR gene), alone and combined, and its interaction with environmental factors and the risk of hepatocellular carcinoma（HCC). Ourstudy will help to understand molecular genetic mechanisms for HCC and toscreen the high-risk population of HCC.MethodsThe hospital-based case–control study was conducted in our study. Thisstudy included1048HCC patients for case. All cases were recruited from thefirst Affiliated Hospital of Guangxi Medical University and Affiliated TumorHospital of Guangxi Medical University during June2007to April2011. Allcases were HCC patients with newly diagnosed by clinical symptom, serumtumor biomarker and histology. All cases should had no previous medicalhistory of malignant tumor of other organ and liver metastasis and did notreceive radiation therapy and/or anticancer drugs. We included1052cance-freecontrols who were recruited from above-mentioned hospitals during the sameperiod and frequency matched by the cases by sex, race, age (±5years). Allcases and controls were residents in Guangxi. The general demographicinformation and related environmental exposure factors of all the objects werecollected by using questionnaire. Each subject donated3ml venous bloodsample. Genomic DNA was isolated from peripheral blood lymphocytes usingthe Phenol-Chloroform method. All these eight selected SNPs were genotypedby the TaqMan MGB assay.The t test and χ2test were used to test the difference of the continuousvariable and the categorieal variable，respectively. Hardy-Weinberg equilibrium(HWE) for evaluation of genotype distributions of the controls was performedby a goodness-of fit χ2test. Odds ratios (ORs) and95%confidence intervals (CIs) were analysed by univariate logistic regression models. And we exploredthe association between the above eight potentially functional SNPs and itsinteraction with environmental factors and the combined effect of all SNPs andthe genetic susceptibility of HCC. All statistical analyses were performed withSAS software(version9.1.3).Results(1) The general characteristics of the subjectsNo statistical differences in the distributions of age, sex, race werefound between cases and controls (P>0.05), respectively. However, the caseswere more likely to be smokers, drinkers, and HBV infection indivuals thanthe controls (P＜0.001).(2)Associations between mTOR, mLST8and RPTOR SNPs and risk ofHCCWe performed Unconditional Logistic Regression model (adjusted by age,sex, race, smoking, drinking status and HBV infection). Compared with the TTgenotype of rs2536(T>C), no statistical association was found between TC orCC genotype and the risk of HCC(TC vs.TT: OR=1.02,95%CI:0.74-1.42; CCvs.TT:OR=0.44,95%CI:0.15-1.42). Compared with the GG genotype ofrs1883965(G>A), no statistical association was found between GA or AAgenotype and the risk of HCC(GA vs.GG: OR=1.10,95%CI:0.78-1.56; AAvs.GG: OR=0.35,95%CI:0.04-2.90). Compared with the TT genotype ofrs3160(T>C), no statistical association was found between TC or CC genotypeand the risk of HCC(TC vs.TT: OR=0.95,95%CI:0.71-1.27；CC vs.TT: OR=0.77,95%CI:0.53-1.12). Compared with the AA genotype of rs26865(A>G), no statistical association was found between AG or GG genotype and the risk ofHCC(AG vs.AA: OR=0.97,95%CI:0.73-1.29； GG vs.AA: OR=1.37,95%CI:0.94-1.99). Compared with the CC genotype of rs3751934(C>A), CA orAA genotype was not associated with HCC risk (CA vs.CC: OR=0.97,95%CI:0.74-1.26；AA vs.CC: OR=0.77,95%CI:0.53-1.16). Compared with theTT genotype of rs1062935(T>C) and rs3751932（T>C）, no statisticalassociation was found between TC or CC genotype and the risk of HCC,respectively (TC vs.TT: OR=1.14,95%CI:0.85-1.52；CC vs.TT: OR=0.99,95%CI:0.69-1.41for rs1062935；TC vs.TT: OR=1.12,95%CI:0.84-1.50；CCvs.TT: OR=0.89,95%CI:0.38-2.09for rs3751932). Compared with the GGgenotype of rs12602885(G>A), GA or AA genotype was not associated with therisk of HCC(GA vs.AA: OR=0.83,95%CI:0.63-1.08；AA vs.GG: OR=0.86,95%CI:0.49-1.50). There were no statistical significance in the above8SNPs inboth dominance model and recessive model.(3)Combine analysisWe found that individuals with two or more risk genotypes exhibitedincreased risk for HCC (OR=1.53,95%CI=1.12-2.10), compared with thosewith less than two unfavorable genotypes.(4) Stratification analysis of HCC risk and combination of eigth selectedSNPsThe increased risk of HCC associated with two or more unfavorablegenotypes was more pronounced among Han race subjects (OR=1.49,95%CI=1.03–2.17), never-smoker (OR=1.76,95%CI：1.20–2.58), never-drinker (OR=1.53,95%CI：1.02–2.22), HBV positive subjects(OR=1.87,95%CI：1.23–2.85). There were no significant gene–environment interactions on the risk of HCC between the combined effects of the risk genotypes and environmentalfactors such asage, sex, race, drinking, smoking statusand HBV infection (P>0.05).ConclusionIn the single-locus analyses, no association between the polymorphism inmTO,,mLST8and RPTOR and the risk of HCC. When combine the riskgenotypeS of the above eight selected SNPs, the combined effect of the aboveeight selected SNPs may increased the risk of HCC.