Influence Of A Single-nucleotide Polymorphism Of The DNA Mismatch Repair-related Gene Exonuclease-1 (rs9350) With Prostate Cancer Risk Among Chinese People

Background:Prostate cancer is a kind of malignant epithelial tumor which grows in prostate. The pathological pattern contains glandular cancer, ductal adenocarcinoma, urothelium carcinoma, squamous-cell carcinoma and adenosquamous carcinoma and 90% of these pathological types are glandular cancer. Thus, generally we informed about prostate cancer means that it is prostate glandular cancer. In 2012,the prostate cancer morbidity is 9.92/100 000 at the place of cancer registration area in china,takes the sixth place of all male malignant neoplasm. The morbidity of the disease is low under age 55,while it is increasing along with the age after age 55,the peak is age 70-80.An earlier morbidity occurs in heredofamilial prostate cancer patients,43% patients are at age younger than 55.In world wild, prostate cancer is one of the most common malignant tumor which affect male’s health, among all the carcinoma in male, prostate cancer ranks at the second place. There are some significant differences of morbidity when the patient come from different places and different races. It is the highest in Australia/New Zealand, Caribbean while it is lowest in Asia and North Africa. According to the report of American Cancer Society, the number of prostate cancer patients is 238950 in USA in 2013, occupies 50% in all malignant tumor,while the death number is 29720.In Europe, there are 382000 new cases in 2880 while the death number is 90000.Although the morbidity in Asia is lower than Europe and America, the rising rate of the morbidity is on the other side. According to the world census report, it is indentified that the rate of prostate cancer morbidity in China is increasing these years. The rising rate of prostate cancer morbidity is 2.1% in 1998-1974 while it is 13.4% in 1994-2002.The risk factor of prostate cancer is still unclear, a few confirmed factors are age, races and hereditary. If there is 2 or more than 2 patients in your family, the risk is increasing by 5-11 times. It is confirmed that compared with non-SNP male, the risk is 9.46 when there are 5 or more than 5 SNPs exsiting.Single Nucleotide Polymorphisms (SNPs) are DNA sequence polymorphisms caused by a single nucleotide mutation during the procedure of DNA sequence deplication transcription. The difference between mutant and SNPs is the rate of variation, less than 1% is called the mutant and more than 1% is called single nucleotide polymorphism. SNPs is a common heritable variation which exsits human genetic variation in the human gene widely,. Among all the polymorphism, the SNPs occupies over 90%. In the human genome each of about 1000 bp is SNP and the number of all SNPs is about 3× 106.A single mutation, it could be a basic group converted caused by transition or transversion, it also could be caused by insertion or deletion of single nucleotides. Generally speaking, SNPs we talked about are mostly caused by transitions and transversions. Most of SNPs are insignificant (such as non-coding region SNPs) because of there is no effects on protein function or gene expressionThere are several kinds of SNPs. About 95% of the SNPs located in the non-coding region, a little fraction of SNPs are located in the gene regulatory region, were known as gene control region SNPs (rSNPs). which is located in the coding region of the gene coding SNPs called SNPs (cSNPs). Furthermore, if cSNPs does not change the amino acid sequence encoded, it could be called synonymous SNPs (sSNPs). But if it change the amino acid sequence, it could be called non-synonymous SNPs or missense SNPs (nsSNPs).Although cSNPs accounts for less percentage in all variation, it means a lot in the research of hereditary disease.Hence, the research of cSNPs draw more attention. There are about 50% nsSNPs in all cSNPs.SNPs are widely exists in human population, at the same time, SNPs could be relatively stable existing from birth to death as a biological marker. Thus, a genetic analysis in the early diagnosis of disease is reality. Nowadays, it is confirmed that SNPs is able to affect the function of DNA, some prostate cancer related SNPs could affect the occurrence, development and prognosis of prostate cancer "by many methods. Thus, SNPs can be able to affect and provide the tumor occurrence and development as a biological marker, provide an effective method of common cancer screening as well.There are two allelic type which is less than microsatellite variability while as the third generation of SNP genetic markers,. Owe to the gaint number of frequency distribution in all of the genome, compared with microsatellite genetic markers it is more stable.lt is only need to analysis positive or negative (+/-) when generally SNPs in the genomic screening process, so it is not hard to operate genotyping analysis automatically. Compared to the first and second generation of genetic markers, are more suitable for exploring population-based genetic condition and other aspects of the study in complex genetic diseases. It has been replaced microsatellite marker technology in the field of genetic research. SNPs were used to explain the phenotypic differences between individuals, different complex diseases susceptibility of different groups or individuals, drug and environmental factors response. It has been widely used in clinical diagnosis, forensics, pathogen detection, genetic diseases, new drug development and other aspects. Common methods of analysis of SNPs can be divided into three categories. The first category is association analysis based genetic epidemiology method, including the research of SNPs in disease susceptibility, drug reactions and other phenotypic differences.The second category is about the analysis in cellular and biochemical levels including enzyme activity and other aspects in cell signaling pathways to illustrate the impact of SNPs on gene function. The third category focus on SNPs impacting on molecular mechanisms of gene expression. Through the role of SNPs in the gene transcription, translation and protein expression to explore the mechanism of SNPs affecting gene function.The research group in Okayama University had screened 48 missense SNPs (non-synonymous SNPs) in cancer-related genes. They found 12 SNPs in 10 genes and these SNPs have a significant impact on the incidence of prostate cancer. This 10 genes include five tumor suppressor genes, two DNA repair genes, a metabolic enzyme gene, a chromosome segregation gene and an apoptosis-related gene. Nine SNPs which are correlated with prostate cancer were first discovered. This 12 SNPs in prediction of prostate cancer risk also has a cumulative effect. The highest risk group’s OR value can be up to 47.4 comparing with the low-risk group. The highest risk group the incidence of prostate cancer in the next 30 years was 29%, while the low-risk group was 0.6% and the lowest risk group was only about 0.2%. Thus, through the integration of multiple tumor-associated SNPs risk to conduct tumor genetics evaluation, can further improve the accuracy and efficiency of prostate cancer screening in high-risk populations. It also can improve the prevention or early diagnosis of prostate cancer.Because of similar geographic and ethnic origin, Chinese population and Japanese population have great similarity in genetic background. These prostate cancer risk SNPs obtained by large-scale screening of the Japanese population may also apply to the Chinese population. In order to test this hypothesis and further expand this research results from Japan into China and other Asian countries, China, Japan, South Korea and Singapore jointly launched an international multi-center study. This study was designed to test the effectiveness of these prostate cancer risk SNPs in other Asian populations. The selected SNPs in this article is derived from the achievement of Okayama University research group and is consistent with multi-center study.Purpose1. To investigate the association between SNPs and the risk of prostate cancer in Chinese population, positive sites to guidance for prostate cancer prevention and early diagnosis. Using positive SNP for prostate cancer prevention and early diagnosis.2. Try to establish a risk model with number of positive single-nucleotide polymorphisms in predicting the risk of prostate cancer among Chinese Han population.MethodFrom January 2009 to April 2013, recruited 253 cases of prostate cancer (Pca) patients and 214 cases of non-prostate cancer patients and healthy volunteers (control group) from Southern Medical University zhujiang Hospital and the first affiliated hospital of Zhejiang university, Peking University Shougang Hosipitol. Case group included biopsy or pathologic diagnosis of prostate cancer patients, the initial onset or referral. Control group included patients with prostate cancer and other malignancies with age matched patients maintained. The could be in the same patient hospitalization or outpatient medical units during the same period. Recorded clinical data such as age at onset, PSA, Gleason score, TNM stage, treatment, and treatment effects and distributed questionnaires to patients. The questionnaires included smoking history, drinking history, family history, diet habit and so on.A 2 mL blood sample was obtained from each participant, and it remained at room temperature for no more than six hours. Genomic DNA was extracted using a TIANamp Blood DNA Kit (TIANGEN Biotech, Beijing, China) according to the manufacturer’s instructions, and was stored at -20℃. We analyzed the Axin2 SNP (rs2240308) and seven SNPs of the other genes (not shown in this paper) using these samples. The genetic analyses were performed using the ABI SNaPshot multiplex system (Life Technologies Corporation, Carlsbad, CA, USA).Statistical analysisWe compared the proportion (percentage) of the each genotype and allele of the SNP [rs9350:G/A] and other seven SNPs in the controls and prostate cancer cases. The association between the SNP and incidence of prostate cancer was analyzed using a logistic regression model. The odds ratio (OR),95% confidence interval (CI) and corresponding p values for the association between the prostate cancer risk and the genotypes or alleles were calculated. The data for each genotype or allele was compared with that of the common homozygote or allele as the reference group. We also stratified our analyses by the age of the patient at diagnosis (< 72 or> 72 years) and by the aggressiveness of the disease (localized or advanced prostate cancer). Localized prostate cancer inclusion criteria are T1-2, N0, M0, Gleason score 2-7, and PSA levels≤ 50 ng/mL. Advanced prostate cancer inclusion criteria are T3/4 or N+ or M+or Gleason score 8-10 or PSA levels> 50 ng/mL.In these analyses, the data were adjusted for the age, smoking status and drinking status. The data are shown as the means ± standard deviation (SD). The Chi-square test was used to compare the distribution of the control males and prostate cancer patients or of the clinical characteristics. The Mann-Whitney U test was also performed to analyze the statistical significance of differences in the age and PSA level at diagnosis. All statistical analyses were conducted using the SPSS software program, version 20.0. The differences were considered to be significant for values of p< 0.05.Results1,SNP analysis of rs9350 in prostate cancerThe allele and genotype frequencies of rs9350 among cases and control subjects are listed in Table 3. The same proportion of rs9350 CC allele (32.8 vs.45.3%) was observed in prostate cancer patients and control subjects. The proportions of rs9350 CT and TT genotypes in prostate cancer patients versus control subjects were 53.0 versus 44.4% and 14.2 versus 10.3%, respectively. Comparedwith the CC genotype, the CT genotype may increase prostate cancer risk (OR=1.648,95% CI=1.112-2.444, P=0.013 and adjusted OR=1.678,95% CI=1.130-2.494, P=0.010). Further, the CT/TT genotypes were significantly associated with increased prostate cancer risk (OR=1.698,95%CI=1.166-2.473, P=0.006 and adjusted OR=1.714,95% CI=1.176-2.500, P=0.005), and the C allele had a significant statistically compared with Tallele (P=0.009) of EXO1 (rs9350).2, SNP analysis of rs9350 for different ages at diagnosisIn stratified analysis, we selected an age at diagnosis of 72 years as the cutoff, with similar numbers of cases above and below the cutoff age. In the>72 years group, the CT/TT genotypes of rs9350 were statistically significant (P=0.032) as well as the C allele compared with the T allele(adjusted OR=1.464,95% CI=0.998-12.147, P=0.041) for prostate cancer risk.3, SNP analysis of rs9350 in different prostate cancer classesIn another stratified analysis, we classified the prostate cancer patients into localized and advanced disease in terms of the aggressiveness. In the localized disease subgroup (controls:all cancer-free patients or healthy men), the CT/TT genotypes of rs9350 were associated with significantly increased prostate cancer risk (adjusted OR=1.798,95% CI= 1.070-3.022, P=0.027).4, SNP analysis of rs9350 for different patient factorsExcept for PSA levels at diagnosis, no significant association was observed between rs9350 and clinical factors, including aggressiveness, Gleason scores, age at diagnosis, smoking status, or drinking status. Subjects with PSA levels of<10 ng/mL were more likely to have the CTVTT genotype than those with PSA levels of>10 ng/mL (P=0.006).Conclusion:this variation in location could have helped obtain convincing results, although the sample size was small. Other studies have demonstrated a significant association between rs9350 and development of pancreatic cancer in American and Taiwanese populations.To our knowledge, our study provides the first evidence for the association between the EXO1 SNP rs9350 and prostate cancer risk in Chinese people.we provided evidence of independent replication for the EXO1 SNP rs9350 associated with prostate cancer risk in China. Although additional studies with larger and more diverse populations and functional analysis of the SNP are necessary to confirm and extend our findings, we believe that the EXO1 SNP rs9350 could be a useful biomarker for assessing predisposition to prostate cancer and early diagnosis of the disease.