Genetic Polymorphisms Of FADD And Susceptibility To Cervical Cancer

Background and Objective:Cervical cancer is the second most common malignancy in women worldwide.Human papillomavirus are the major cause of cervical cancer and one of the underlying mechanisms is the interaction of their oncoproteins E6 and E7 with cellular proteins P53 and RB1,which interferes with normal cellular apoptosis and cell cycle.FAS-associated via death domain(FADD) is an important player both in apoptosis pathways and in cell cycle regulation,and implicated in the development of various human cancers.The present study examined the association between polymorphisms in FADD and susceptibility to cervical cancer and its underlying mechanism.Methods:Coding regions,5'UTR,3'UTR and 5' flanking region of FADD were resequenced in 30 Chinese adults to detect polymorphisms.The associations between the identified polymorphisms in FADD and risk of cervical cancer were examined in a case-control analysis consisted of 463 patients with cervical cancer and 876 controls. PCR-RFLP was used to identify genotypes and unconditional logistic regression model was used to compute the odds ratio(OR) and its corresponding 95%confidence interval (CI).Electrophoretic mobility shift assays and dual-luciferase reporter gene assays were used to examine the functions of the polymorphisms.Results:Three genetic variations,i.e.-16C/T,255A/G and 3859TGT/-(3N ins/del,3N I/D) were detected,which are in some extent of linkage disequilibrium.We showed that heterozygotes of these polymorphisms were all associated with significantly increased risk for cervical cancer,with the ORs(95%CI) being 1.41(1.06-1.88),1.48(1.16-1.89) and 1.34(1.05-1.72),for-16CT,255AG and 3859 3N ins/del genotypes,respectively, while homozygotes of each variant seemed not to be associated with risk of the cancer. Stratification analyses revealed that the risk seemed to restrain in squamous cell carcinoma developed in women more than 35-year old.The frequency of the -16CC genotype was significantly higher in advanced cervical cancer(stageâ…¡to stageâ…£) than in early stage cancer(stage 0 andâ… ),while 255A/G and 3859 3N ins/del polymorphisms appeared not to be associated with cancer progression.Subjects carrying the -16TT/255AG/3859ID(OR=2.52,95%CI=1.49-4.27) or-16CT/255AG/3859ID(OR =1.71,95%CI=1.23-2.38) genotype had significantly increased risk compared with the -16CC/255GG/3859â…¡genotype.Reporter gene assay showed that the region between -304 bp and 297 bp had the highest promoter activity,while the regions between -1070 bp and -780 bp and -780 bp and -304 bp displayed activities of positive and negative regulation,respectively.The 5' untranslated region also exhibited transcriptional activity. For the 3859 3N ins/del polymorphism in the 3' untranslated region,the deletion allele had decreased reporter gene expression compared with the insertion allele.Haplotypes C_-16G₂₅₅,T_-16G₂₅₅ and C_-16A₂₅₅ had higher promoter activity than haplotype T_-16A₂₅₅, suggesting that both -16C and 255G alleles have higher transcription activity than their counterparts,but it seemed that epistasis existed between these two polymorphisms. Electrophoretic mobility shift assay showed that the -16C allele binds to potential Sp1 transcription factor more robustly than the -16T allele does.However,the 255G and 255A alleles did not show any difference in binding to nuclear proteins.Conclusion:FADD polymorphisms are associated with increased risk for developing cervical cancer,especially cervical squamous cell carcinoma,which might be caused by their impact on transcription and/or translation regulation of the gene.