| BackgroundEpithelial ovarian cancer is not only very common among gynecological carcinomas,but also the most lethal malignant. The main reason is owing to a lack of symptoms inearly stage and effective measures for early diagnosis. Though the pathogenesis ofepithelial ovarian cancer is still fully unknown, it has been reported in previous study thatchanging of some genes were observed in epithelial ovarian cancer patients, such as p53,PTEN, BRCA1/BRCA2, HER2, KRAS and PI3K gene, which suggested that genomicalterations play an important role in modulating susceptibility to epithelial ovarian cancer.Single nucleotide polymorphism (SNP) is the most common and simplest sequencevariation, but is related with phenotypic difference, susceptibility to disease andresponding to drugs. Therefore, it is very likely a good way to identifying SNPs of predisposing genes for establishing high-risk groups and achieving early diagnosis forepithelial ovarian cancer, realizing the concept of personalized medicine and gene targettherapy.Apurinic/apyrimidinic endonuclease1(APE1) is an important multifunctionalprotein, which plays an essential role in the base excision repair (BER) pathway,regulates transcription and participates in cell apoptosis. Some studies suggested thatAPE1expressed differently in normal ovarian tissue and epithelial ovarian cancer tissue,and between ovarian sensitive cells and resident cells to platinum. Furthermore, manyepidemiological studies suggested that SNPs in APE1may confer individuals’susceptibility to cancers. Based on the previous studies, we speculate that polymorphismsof APE1may be associated with individual susceptibility to epithelial ovarian cancer.Firstly, in order to choose significant SNPs for the further experimentation, SNPs ofAPE1in epithelial epithelial ovarian cancer cell lines were examined. Secondly, therelationship between SNPs of APE1and risk to epithelial ovarian cancer wasinvestigated through hospital-based, case-control study about84epithelial ovariancancers and126healthy women who were all northwestern Han Chinese.Purpose1. To lay the foundation for the case-control study by screening SNPs of APE1inepithelial epithelial ovarian cancer cell lines.2. To investigate the associations between SNPs of APE1and epithelial ovarian cancersusceptibility through a case-control study.Contents1. Chose relevant SNPs on the basis of HapMap database and dpSNP database.2. Extracted DNA from the cells of A2780, SKOV3, HO-8910, A2780/DDP andSKOV3/DDP, then amplified the aim gene fragment by PCR, and detected the genetypes of each polymorphism among all the cells by sequencing. The results wereanalyzed by Chromas2software. And then, according to HapMap database anddpSNP database chose the significant SNPs. 3. Collected blood samples from84epithelial ovarian cancer patients and126healthywomen who were all Han in northwestern of China. Extracted DNA from the everysample, and detected Genotypes of rs1760944and rs1130409by PCR andsequencing. The sequencing results were analyzed by Chromas2software andcompared with sequence alignment of APE1in GenBank by DNAMAN V6software.The distribution characters of genotypes, and relationship between SNPs and risk toepithelial ovarian cancer were analyzed by SPSS16.0. Demographic characteristicsbetween cases and controls used student-t test and chi-squared test to compare. Foreach SNP in the case and control subjects, the chi-squared test was used to test forHardy-Weinberg equilibrium (HWE). Distribution analyses of rs1130409andrs1760944genotypes between the cases and controls used multiple logisticregression analysis. Stratified analysis was used to study relationships between thegenotypes and characteristic variables of cases and controls. Association betweengenotype distributions and clinicopathological characteristics of the cases wereanalyzed by chi-squared test. To further explore associations between the two SNPsand epithelial ovarian cancer susceptibility, haplotypes and their frequencies wereestimated by PHASE2.1. P value of＜0.05was considered significant in allstatistical tests, and all P values were based on two-way tests.Results1. Referring to HapMap database and dpSNP database, a total of10SNPs in APE1havebeen identified in CHB, rs1760944, and according to their distribution characters,rs1760944, rs1130409and rs2307486were chose as the screening SNPs.2. Genotypes of rs1760944in A2780, A2780/DDP, SKOV3and HO-8910cells were allGG, and in SKOV3/DDP cell was TT. Genotypes of rs1130409in A2780andA2780/DDP cells were all TG, and in HO-8910, SKOV3and SKOV3/DDP cellswere all TT. Genotypes of rs2307486in A2780, SKOV3, HO-8910, A2780/DDP andSKOV3/DDP cells were all homozygous AA. The results suggested that in the fivecell lines polymorphisms of rs1760944and rs1130409were observed, but rs2307486 was not. So, rs1760944and rs1130409were elected into the clinical case-controlstudy.3. No statistical differences were found for the age, menarche age, gravidity, parity andmenopausal status between the cases and controls (P>0.05). Genotype frequencies ofthe two SNPs in case and control groups conformed by Hardy-Weinberg equilibrium(Prs1760944=0.074, Prs1130409=0.371for cases; Prs1760944=0.386, Prs1130409=0.241forcontrols).4. For rs1130409polymorphism, TG/GG genotype and G allele were associated with adecreased risk (aOR=0.468,95%CI:0.235-0.934for the TG versus TT;aOR=0.229,95%CI:0.105-0.500for the GG versus TT; aOR=0.678,95%CI:0.348-0.741for the G allele verus T allele) to epithelial ovarian cancer.However, the rs1760944polymorphism was not found be associated with risk toepithelial ovarian cancer,5. In the stratified analyses, it was found that when TG/GG genotype versus TTgenotype the lower risk was more evident in subgroups of age≥50years (aOR=0.756,95%CI:0.611-0.935), menarche age≥15years (aOR=0.893,95%CI:0.713-1.119),grabidity≥3times (aOR=0.629,95%CI:0.466-0.848), parity≥3times (aOR=0.655,95%CI:0.464-0.925) and postmenopausal women (aOR=0.769,95%CI:0.618-0.957).However, the distributive differences of genotypes in the stratified analyses aboutclinicopathologic charaterristics were not found. In stratified analyses aboutcharateristic variables and clinicopathologic charaterristics for rs1760944, nodistributive differences of genotypes were found.6. In the haplotype analysis, a decreased the risk to epithelial ovarian cancer were foundfor T-G and G-G heplotypes, but the G-T heplotype was not found.Conclusion1. This study suggested that in Chinese Han population the APE1rs1130409polymorphism may be relevant with epithelial ovarian cancer susceptibility. However,rs1760944polymorphism was not found be associated with epithelial ovarian cancer suscepibility, neither were the distributive differences of genotypes in the stratifiedanalyses.2. For analysis of rs1130409polymorphism, TG/GG genotype and G allele wereassociated with a decreased risk to epithelial ovarian cancer, moreover, thisprotective effect was more evident in subgroups of age≥50years, menarche age≥15years, grabidity≥3times, parity≥3times and postmenopausal women. Distributiondifference for genotypes of rs1130409was not found in stratified analyses aboutclinicopathologic charaterristics.3. In stratified analyses about charateristic variables, no association were found betweenrs1760944polymorphism and epithelial ovarian cancer suspebility. Distributiondifference for genotypes of rs1760944was not found in stratified analyses aboutclinicopathologic charaterristics.4. The four heplotypes distributed differently in northwestern Chinese Han women,Furthermore, T-G and G-G heplotypes decreasing the risk to epithelial ovarian cancerbut nothing on the G-T heplotype verusing T-T heplotype, which suggested thatrs1130409polymorphism may turn out to be more contributing than rs1760944polymorphism to epithelial ovarian cancer suscepibility, and inernal correlationbetween rs1760944and rs1130409may be not obvious. |
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