| BackgroundEndometriosis (EM) is a chronic common gynecological disease characterized by growth of endometrial tissue in sites other than the uterine cavity. In the Chinese population, EM affects10%to15%of women in their reproductive age with a growing trend in recent years. EM is a benign condition, however, the clinical features of EM are varied. Furthermore, EM shows an aggressive clinical course, with a high tendency of recurrence and distant metastasis. There is still no specific method of EM clinical treatment. Although EM is a kind of common gynecologic disease, its pathogenesis is still controversial.In the past years, many hypothesis to the pathogenesis of EM have been developed, such as the theory of menstrual blood reflux, epithelial metaplasia, abnormity of Mullerian tube, immune inflammatory diseases, distant dissemination of lymph and blood vessels, harmful pathogenic substances and genetics factor, etc. However, none of these theories alone can clearly illustrate the pathogenesis of EM. Based on the theories above, it is considered that susceptibility to EM is a consequence of genetic predisposition.One of the most common genetic variations in human is the single nucleotide polymorphism (SNP) which can lead to the diversity of individual susceptibility to a disease. The SNPs of a gene may increase the risk to EM by affecting abnormal expression of the geneEM is treated as a tumor-liked disease clinically, but how far the distance of EM between benign disease and malignant tumor exists is still not clear. At present, many studies have been focused on the role of tumor-associated gene, especially the tumor suppressor gene that may play an important role in the pathogenesis of EM.The tumor suppressor gene P53is one of the most studied genes that found mutated in many human cancers. P53plays an important role in regulation of cell growth, and the expression and function of P53protein has been found closely correlated to mutation of P53gene. The P53gene, which induces cell cycle interruption, apoptosis or DNA damage repair, negatively regulates the cell cycle and loss of function mutations of P53is required for tumor formation. Furthermore, P53gene polymorphism is likely to be relevant to the development of EM. Different results have been reported when studies conducted in different ethnic populations simply because of the different genetic backgrounds. However, in China, especially for Chinese population, there is still no report the association between SNP and EM on P53gene. In this study, in order to investigate the association of single nucleotide polymorphisms (SNP) in tumor suppressor gene P53with the risk of endometriosis in Chinese Han women, the SNP of P53gene (rs1042522,C/G) was genotyped by PCR-Sequence specific primer (PCR-SSP) and sequencing in460endometriosis (EM) patients,113patients with endometrial carcinoma and650matched unrelated controls. A meta-analysis involving7literatures which were eligible for the criteria to investigating the P53(rs1042522) SNP, including968endometriosis patients and1282controls case, were also conducted.ObjectiveThis study is mainly focused on the associations between the polymorphism of tumor related genes (the tumor suppressor gene P53) and the genetic susceptibility to EM in Chinese Han women.Subjects and Methods1. Subj ects of study1.1Subjects All patients in this study were received an abdominal and pelvic surgery in department of Obstetric and Gynecology of Nanfang Hospital, Zhujiang Hospital and Foshan First People’s Hospital from October2008to October2011. In total,460EM patients and650controls who had an operation due to ectopic pregnancy, tubal reversal, tubal ligation, laparoscopic hydrotubation, ovarian simple cyst were collected as control. Another113endometrial carcinoma patients who received D&C (dilation and curettage) or pelvic surgery in department of Obstetric and Gynecology of Nanfang Hospital, Zhujiang Hospital were also recruited. All cases were confirmed by operation and pathology. There is no significant difference among the three groups of subjects with age (P>0.05).1.2Accepting criteria of meta-analysis1) the purpose and statistical method of the literatures were similar, and the data was complete;2) all EM cases were confirmed by operation and pathology, not including other complication;3) all non-EM cases were confirmed by pathology or healthy women;4)the allele frequencies must fit the Hardy-Weinberg equilibrium.2Methods 2.1experimental methods2.1.1DNA extraction Genomic DNAs were extracted from peripheral blood following the instructions of E-Z96TM Blood DNA Kit.2.1.2SNP genotyping The SNP of P53gene (rs1042522) is genotyped by PCR-sequence specific primer (PCR-SSP) and sequencing.2.2Meta-analysis Published case-control studies about the association of P53(rs1042522) polymorphism on endometriosis were searched and screened in PubMed database, EMBase database, database of Wanfang, China National Konwledge Internet(CNKI), and database for Chinese Technical Periodicals(VIP), using the key words:endometriosis、P53(tumor suppressor gene P53)、SNP(s)、 gene、genetic、polymorphism(s). Finally, there were7literatures including968endometriosis patients and1282controls case, which were eligible for the criteria to investigating the P53(rs1042522) SNP. The meta-analysis was conducted using RevMan5.0software.2.3Statistic analysis2.3.1Distributions of allelic and genotypic frequencies in each group were calculated by direct counting. The statistical analysis were conducted by SPSS13.0. Chi-square test is used to determine the fitness of Hardy-Weinberg equilibrium. The association between EM and the polymorphisms were accessed by Chi-square test Statistical differentce of allele and genotype frequencies among three groups were examined using Chi-square test. Relative risk was described by odds ratio (OR) and95%confidence interval (95%CI).2.3.2RevMan5.0software was used for meta-analysis. Firstly, statistical heterogeneity analysis was conducted to examine the effect size with Chi-square test to determine I2. I2measures the share of heterogeneity in the effect size, if I2≤50%, it means that there was no heterogeneity, a fixed effect model should be chosen in following analysis; otherwise, when I2>50%, it means that there is heterogeneity, a random effects model should be chosed. The publication bias is evaluated by funnel plot, relative risk is described by odds ratio (OR) and95%confidence interval (95%CI).Results1. Distribution of age of the three groups The average age is35.6±7.2years in the EM group; the average age is34.8±6.3years in the control group; and the average age is48.8±5.8years in the endometrial carcinoma group. There is no significant different among the three groups of subjects with age(P>0.05).2. Distribution of P53gene (rs1042522) polymorphism in three groups One SNP of P53gene (rs1042522, G/C) was genotyped in Chinese Han women, the allele frequencies of the three groups were fitted with the Hardy-Weinberg equilibrium (P>0.05).3. The single SNP of P53gene (rs1042522, G/C) and the genetic susceptibility to EM3.1Distribution of allelic and genotypic frequencies between EM and control groups The G and C allele frequencies in EM and control groups were47.0%,53.0%and55.0%,45.0%, respectively. The GG, GC and CC genotype frequencies in the two groups were22.0%,50.0%,28.0%and31.7%,46.6%,21.7%, respectively. The alleles and genotypes frequencies were statistical significances between the two groups (x2=13.958, P<0.01and χ2=14.341, P<0.01). C allele increaseed the risk to EM at1.179time (95%CI was1.082-1.284), while allele G reduced the risk of EM0.854time (95%CI was0.785-0.929). Compared to the GG genotype, the GC genotype increased the risk to EM with OR of1.548(95%CI was1.153-2.081), while the CC genotype increased the risk to EM with OR of1.865 (95%CI was1.326-2.625).3.2Distribution of allelic and genotypic frequencies between endometrial carcinoma and control groups The G and C allele frequencies in endometrial carcinoma and control groups were42.5%,57.5%and55.0%,45.0%, respectively. The GG, GC and CC genotype frequencies in the two groups were16.8%,51.3%,31.9%and31.7%,46.6%,21.7%, respectively. The alleles and genotypes frequencies were statistical significances between the two groups (x2=12.124, P<0.01and x2=11.967, P<0.01). Allele G increased the risk to endometrial carcinoma1.278time (95%CI was1.126-1.452), while allele C reduced the risk of endometrial carcinoma0.772time (95%CI was0.658-0.906). Compared to the genotype GG, the GC and CC carries are more likely to be affected by endometrial carcinoma with OR of2.074(95%CI was1.197-3.599), and2.864(95%CI was1.557-5.263), respectively.3.3Distribution of allelic and genotypic frequencies between EM and endometrial carcinoma groups The G and C allele frequencies between EM and endometrial carcinoma groups were47.0%,53.0%and42.5%,57.5%, respectively. The GG, GC and CC genotype frequencies between two groups were22.0%,50.0%,28.0%and16.8%,51.3%,31.9%, respectively. There were no statistical significances in the allele and genotype distributions between the two groups (χ2=1.456, P>0.05and χ2=1.636,P>0.05).4The meta-analysis of the potential association between SNP of P53(rs1042522) with the risk of endometriosis4.1Distribution of allele frequencies Significant differences were found between the frequencies of the G allele (P=0.0002; OR=0.74,95%CI was0.66-0.84) and C allele (P=0.0002; OR=1.34,95%CI was1.18-1.52), respectively.4.2Distribution of genotype Significant differences were found between the frequencies distribution of GG genotype (P=0.0004; OR=0.66,95%CI was 0.45-0.96) and CC genotype (P=0.002; OR=1.19,95%CI was0.74-1.91), respectively. However, there was no evidence for association to GC genotype (P>0.05).Conclusion1. The study suggests that the polymorphism of P53gene (rs1042522) is significant associated with the susceptibility to EM in Chinese Han women.2. The study suggests that the polymorphism of P53gene (rs1042522) is significant associated with the susceptibility to endometrial carcinoma in Chinese Han women.3. The study suggests that allele C of P53gene (rs1042522) could increase the risk to both EM and endometrial carcinoma in Chinese Han women.4. The study suggests that the GC and CC carries are more likely to be affected to both EM and endometrial carcinoma in Chinese Han women.5. The P53gene (rs1042522) SNP may be associated with the risk of endometriosis by meta-analysis.6. The GG genotype or the G allele of the P53gene (rs1042522) SNP may reduce the risk of developing EM, while the C allele could significantly increase the risk to EM.7. The results indicate that the mechanism of endometriosis might be more similar to carcinoma from the hereditism point of view. |
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