Synergistic effect of interleukin-6 promoter (IL6 -634C/G) and intercellular adhesion molecule-1 (ICAM-1 469K/E) gene polymorphisms on the risk of endometriosis in Japanese women

Association between polymorphisms of cytokine genes and endometriosis: A comprehensive systematic review and meta-analysis

INTRODUCTION

There is abundant evidence to suggest that cytokines play a part in the mechanisms responsible for the formation of endometrium heterotopy. Cytokine synthesis is not only determined by the body's immunological reactivity but also by polymorphisms in the immune regulatory genes. The study of these polymorphisms in the immune regulatory genes offers up new possibilities in terms of prognosticating the risk of endometriosis and susceptibility to its treatment. The purpose of this comprehensive systematic review and meta-analysis was to investigate whether or not cytokine gene polymorphisms were linked to an increased chance of endometriosis.

METHODS

By searching MEDLINE, Scopus, and Web of Science databases, the relevant studies were identified. The odds ratio (OR) with 95% confidence interval (CI) was used to assess the association between TNF-α/IL-10/IL-6/TGF-β/IFN-γ/IL-1β gene polymorphisms and endometriosis risk.

RESULTS

A total of 5128 cases and 5334 controls in 32 eligible studies were included in the meta-analysis. Overall, results indicated the negative association between the cytokine gene polymorphisms and endometriosis in the dominant model of TNF-α (rs1799964): [OR] = 0.64, [CI]: 0.46-0.89) and a positive association in IFN-γ a13 allele: OR= 1.45, [CI]: 1.07-1.98; and IL-10 (rs1800872): [OR]= 1.60, [CI]: 1.21-2.12).

CONCLUSION

The present study suggests that IL-10 (rs1800872) and IFN-γ a13 allele may be a risk factors for endometriosis. Also, TNF-α (rs1799964) is associated with decreased susceptibility to endometriosis.

Polymorphisms and endometriosis: a systematic review and meta-analyses

BACKGROUND

Endometriosis is an estrogen-dependent gynecological disorder that affects at least 10% of women of reproductive age. It may lead to infertility and non-specific symptoms such as chronic pelvic pain. Endometriosis screening and diagnosis are difficult and time-consuming. Late diagnosis (with a delay ranging from 3.3 to 10.7 years) is a major problem and may contribute to disease progression and a worse response to treatment once initiated. Efficient screening tests might reduce this diagnostic delay. As endometriosis is presumed to be a complex disease with several genetic and non-genetic pathogenic factors, many researchers have sought to identify polymorphisms that predispose to this condition.

OBJECTIVE AND RATIONALE

We performed a systematic review and meta-analysis of the most regularly reported polymorphisms in order to identify those that might predispose to endometriosis and might thus be of value in screening.

SEARCH METHODS

The MEDLINE database was searched for English-language publications on DNA polymorphisms in endometriosis, with no date restriction. The PubTator text mining tool was used to extract gene names from the selected publications' abstracts. We only selected polymorphisms reported by at least three studies, having applied strict inclusion and exclusion criteria to their control populations. No stratification based on ethnicity was performed. All steps were carried out according to PRISMA guidelines.

OUTCOMES

The initial selection of 395 publications cited 242 different genes. Sixty-two genes (corresponding to 265 different polymorphisms) were cited at least in three publications. After the application of our other selection criteria (an original case-control study of endometriosis, a reported association between endometriosis and at least one polymorphism, data on women of reproductive age and a diagnosis of endometriosis in the cases established by surgery and/or MRI and confirmed by histology), 28 polymorphisms were eligible for meta-analysis. Only five of the 28 polymorphisms were found to be significantly associated with endometriosis: interferon gamma (IFNG) (CA) repeat, glutathione S-transferase mu 1 (GSTM1) null genotype, glutathione S-transferase pi 1 (GSTP1) rs1695 and wingless-type MMTV integration site family member 4 (WNT4) rs16826658 and rs2235529. Six others showed a significant trend towards an association: progesterone receptor (PGR) PROGINS, interCellular adhesion molecule 1 (ICAM1) rs1799969, aryl-hydrocarbon receptor repressor (AHRR) rs2292596, cytochrome family 17 subfamily A polypeptide 1 (CYP17A1) rs743572, CYP2C19 rs4244285 and peroxisome proliferator-activated receptor gamma (PPARG) rs1801282), and 12 showed a significant trend towards the lack of an association: tumor necrosis factor (TNF) rs1799964, interleukin 6 (IL6) rs1800796, transforming growth factor beta 1 (TGFB1) rs1800469, estrogen receptor 1 (ESR1) rs2234693, PGR rs10895068, FSH receptor (FSHR) rs6166, ICAM1 rs5498, CYP1A1 rs4646903, CYP19A1 rs10046, tumor protein 53 (TP53) rs1042522, X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1) rs25487 and serpin peptidase inhibitor clade E member 1 (SERPINE1) rs1799889; however, for the 18 polymorphisms identified in the latter two groups, further studies of the potential association with the endometriosis risk are needed. The remaining five of the 28 polymorphisms were not associated with endometriosis: glutathione S-transferase theta 1 (GSTT1) null genotype, vascular endothelial growth factor alpha (VEGFA) rs699947, rs833061, rs2010963 and rs3025039.

WIDER IMPLICATIONS

By carefully taking account of how the control populations were defined, we identified polymorphisms that might be candidates for use in endometriosis screening and polymorphisms not associated with endometriosis. This might constitute the first step towards identifying polymorphism combinations that predispose to endometriosis (IFNG (CA) repeat, GSTM1 null genotype, GSTP1 rs1695, WNT4 rs16826658 and WNT4 rs2235529) in a large cohort of patients with well-defined inclusion criteria. In turn, these results might improve the diagnosis of endometriosis in primary care. Lastly, our present findings may enable a better understanding of endometriosis and improve the management of patients with this disease.

Defining the genetic profile of endometriosis

Endometriosis is a pathological condition which has been extensively studied, since its pathophysiology stems from a broad spectrum of environmental influences and genetic factors. Familial studies aim at defining inheritance trends, while linkage analysis studies focus on the identification of genetic sites related to endometriosis susceptibility. Genetic association studies take into account candidate genes and single nucleotide polymorphisms, and hence target at unraveling the association between disease severity and genetic variation. The common goal of various types of studies is, through genetic mapping methods, the timely identification of therapeutic strategies for disease symptoms, including pelvic pain and infertility, as well as efficient counselling. While genome-wide association studies (GWAS) play a primary role in depicting genetic contributions to disease development, they entail a certain bias as regards the case-control nature of their design and the reproducibility of the results. Nevertheless, genetic-oriented studies and the implementation of the results through clinical tests, hold a considerable advantage in proper disease management. In this review article, we present information about gene-gene and gene-environment interactions involved in endometriosis and discuss the effectiveness of GWAS in identitying novel potential therapeutic targets in an attempt to develop novel therapeutic strategies for a better management and treatment of patients with endometriosis.

Epidemiologic Factors Associated with Endometriosis in East Asia

Aim

With a perplexing pathogenesis and an incidence rate of approximately 10% among women of reproductive age, endometriosis affects more women in Asia than in any other continent in the world. This paper reviews the available data on the epidemiology and risk factors associated with endometriosis in East Asia.

Methods

Included studies were published between January 2000 and December 2016. Articles were required to include East Asian patients with a diagnosis of endometriosis and to study epidemiology, such as the prevalence and/or incidence, associated with inherited, environmental, and/or lifestyle factors. A total of 65 candidate articles were retrieved and 22 were included in the final review.

Results

Only one study provided an estimate of prevalence (6.8%). Short menstrual cycle, family history of endometriosis, and some genetic polymorphisms are associated with the risk of developing endometriosis. Smoking, lower body mass index, and lower parity associated with increased risk of endometriosis were suggested as modifiable factors. Limitations of this study include the poor quality of data identified, and the language barriers behind the study retrieval.

Conclusions

Data on the epidemiology of endometriosis in the East Asian populations are limited. The available data that examine potential genetic factors do not unveil whether such factors directly contribute to the increased risk of endometriosis. Further extensive studies on endometriosis in Asian women are required to improve the management of this disease.

Polymorphisms of ICAM-1 and IL-6 genes related to endometriosis in a sample of Brazilian women

PURPOSE

This study investigated the possibility of K469E (rs5498) and G241R (rs1799969) polymorphisms, in ICAM-1 gene, and G634C (rs1800796), in IL-6 gene, being associated with the occurrence of endometriosis in a sample of Brazilian women.

METHODS

We genotyped 200 women (100 in control group and 100 in endometriosis group) by PCR-RFLP technique for G634C, K469E, and G241R polymorphisms.

RESULTS

No significant difference was observed in genotypic frequency between control and endometriosis groups for G634C and K469E polymorphisms (p = 0.61 and p = 0.22, respectively). In addition, no significant difference between stages I-II and III-IV of the disease was found for both SNPs (p = 0.63 and p = 0.24, respectively). All individuals were wild homozygotes for G241R polymorphism.

CONCLUSION

This study suggests that polymorphisms K469E, G241R, and G634C are not associated with increased susceptibility to endometriosis in Brazilian women.

Association of the intercellular adhesion molecule-1 (ICAM-1) gene polymorphisms with endometriosis: a systematic review and meta-analysis

BACKGROUND

Reported associations of the G241R and K469E polymorphisms of the intercellular adhesion molecule-1 gene (ICAM-1) gene with endometriosis have differed in magnitude.

MATERIALS AND METHODS

In a meta-analysis of six published case-control studies (from five articles), we estimated risk [odds ratio (OR) 95 % confidence intervals (CI)] of associations with these polymorphisms using the Review Manager 5.3 software.

RESULTS

Based on 1213 cases and 1103 controls, overall analysis showed significant increased risk in the homozygous (OR 2.83, 95 % CI 0.99-8.10, p = 0.05), dominant (OR 1.86, 95 % CI 1.00-3.46, p = 0.05) and codominant (OR 2.15, 95 % CI 1.06-4.35, p = 0.03) models. Confined to the studies in Hardy-Weinberg Equilibrium erased the significance (OR 1.59-2.59, 95 % CI 0.81-8.22, p = 0.10-0.15). Asian effects were variable (OR 0.93-1.09, p = 0.50-0.57), but Caucasian effects were not (OR 4.09-13.60, p < 0.0001). Independent data for the late stages of endometriosis suggest protection of the ICAM-1 K469E polymorphism among the Asians (OR 0.91-0.95, p = 0.35-0.71). These effects were weak but non-heterogeneous (P heterogeneity = 0.17-0.57, I (2) = 0-40 %).

CONCLUSION

In summary, strengths of the overall effects were consistency, significance and robustness but limited by their high heterogeneity. These strengths and limitations were also observed in the Caucasian subgroup which when tested for interaction against the contrasting Asian effects, highlighted Caucasian susceptibility (p = 0.004-0.01). The findings are an interplay of strengths and limitations, which warrant awareness of their interpretation as susceptibility markers for this disorder.

Association of intercellular adhesion molecular-1 gene polymorphism in ischemic stroke patients

BACKGROUND

Ischemic stroke (IS) is a prevalent disease causing a body disability, the third leading cause of death in Taiwan. It shows that the level of intercellular adhesion molecular-1 (ICAM-1) in IS patients is higher than control subjects.

OBJECTIVE

This study is to investigate the possible association of ICAM-1 (G1548A) polymorphism in IS patients.

MATERIALS AND METHODS

A total of 646 subjects were enrolled in this study, including 312 IS patients, and 334 controls without a history of symptomatic IS. The ICAM-1 (G1548A) polymorphism was analyzed by polymerase chain reaction and restriction fragment length polymorphism. Clinical factors were also determined.

RESULTS

The frequencies of the ICAM-1 (G1548A) polymorphism for G/G, G/A, and A/A were 74.8%, 23.9%, and 0.3%, respectively, in healthy controls, and 62.8%, 32.1%, and 5.1%, respectively, in patients. The frequency of the ICAM-1 (G1548A) A allele (21.2% versus 13.2%, respectively; P = 0.007) and the carriers of the ICAM-1 (G1548A) A allele (37.2% versus 25.2%; P = 0.019, OR 1.76, 95% CI 1.1-2.83) are great in IS patients compared with healthy controls. There is a higher risk of IS associated with homozygosity for the ICAM-1 (G1548A) A allele (AA genotype) compared with the control population (5.1% vs. 0.3%, respectively, P = 0.04; OR 5.1, 95% CI 1.19-21.66). We also observed both hypertension and diabetes has shown a positive association with IS.

CONCLUSIONS

The ICAM-1 (G1548A) polymorphism was associated with independent risk factor for the development of IS.

Interleukin-6 polymorphism and bronchopulmonary dysplasia risk in very low-birthweight infants

BACKGROUND

The aim of the present study was to evaluate the role of interleukin (IL)-6-634 polymorphism in neonatal disorders such as bronchopulmonary dysplasia (BPD) and periventricular leukomalacia (PVL) in very low-birthweight (VLBW) infants.

METHODS

This prospective cohort study included 202 infants (gestational age at birth, 23-34 weeks; birthweight, 500-1499 g). Genotypic analysis (polymerase chain reaction-restriction fragment length polymorphism) was performed with DNA extracted from whole-blood samples.

RESULTS

Genotype distribution (66.8% CC, 28.2% CG, 5.0% GG) was similar to that in the adult Japanese population. BPD occurred in 85 infants (42.1%) among 202 VLBW infants. The duration of O(2) therapy in infants with CG/GG genotypes was significantly longer than that in infants with the CC genotype (CG/GG vs CC: 40.3 ± 52.2 days vs 28.4 ± 32.6 days, P < 0.05), but the prevalence of BPD was not associated with the CG/GG genotype (CG/GG, 40.0%; CC, 46.3%, P= 0.24). Infants with CG/GG genotypes were more likely to have received postnatal corticosteroid therapy for BPD than those with the CC genotype (CG/GG vs CC: 20.9% vs 11.1%, P = 0.05). PVL occurred in six infants (3.0%). There was no significant difference in the prevalence of PVL among IL-6-634 polymorphisms (CG/GG, 3.0%; CC, 3.0%, P = 0.65).

CONCLUSIONS

IL-6-634 polymorphism is associated with duration of oxygen therapy in VLBW infants. This suggests that the IL-6-634 polymorphism G allele is an aggravating factor of BPD. IL-6-634 polymorphism is not associated with PVL.

DNA hypomethylation of the COX-2 gene promoter is associated with up-regulation of its mRNA expression in eutopic endometrium of endometriosis

Background

Accumulated evidence reveals that cyclooxygenase-2 (COX-2) was overexpressed in eutopic endometrium of endometriosis, which may play a critical role in the pathogenesis of endometriosis. However, few studies have been performed to explore the molecular mechanisms underlying the abnormal high expression of COX-2 in endometriosis. Considering the fact that a number of recent studies have shown DNA methylation affecting some genes in endometriosis, the present study was therefore aimed to determine whether the observed high expression COX-2 in endometriosis is caused by the hypomethylation of CpG island within the promoter of this gene.

Methods

The endometrial tissues were collected from 60 women with endometriosis (endometriosis group) and 20 women without endometriosis (control group). The methylation status of COX-2 was examined by methylation specific PCR. Quantitative real-time RT-PCR was performed to measure COX-2 mRNA level in endometrial tissues.

Results

The frequency of promoter hypermethylation of COX-2 was lower in eutopic endometrium of the endometriosis group (41.7%) than that in the control group (75.0%), P < 0.05. COX-2 mRNA level in the eutopic endometrium of the endometriosis group was 2.61-fold higher than that in the control group (P < 0.01). COX-2 mRNA level in unmethylated endometrium of the endometriosis group or the control group was 2.39-fold and 2.66-fold, respectively, higher than that in the methylated endometrium of the same group (P < 0.01).

Conclusions

The hypomethylation within the promoter of COX-2 may be responsible for the elevated gene expression in eutopic endometrium of endometriosis.

Combined effect of cytokine gene polymorphisms on end-stage knee osteoarthritis from Chinese Han population

The mechanism of osteoarthritis (OA) is not well understood. Cytokines have been implicated in the episode, and there is increasing evidence that the host's cytokine response is genetically determined. We determined the predictive value of IL-634G./C, ICAM-1 469 K/E and IL-10-1082A/G, -819T/C and -592A/C gene polymorphisms on knee OA. The study included 1007 patients with end-stage knee OA and 910 healthy controls. Genomic DNA was prepared from peripheral blood leukocytes. Genotypes and allele frequencies were determined using restriction fragment length polymorphism analysis of polymerase chain reaction products. No significant difference in the IL-10 promoter allele or haplotype frequencies between end-stage knee OA and controls was found. Patients with end-stage knee OA showed a significantly higher prevalence of IL-6-634G/ICAM-1 469E carrier than that in controls (P = 0.017). Results indicate that IL-6-634G/ICAM-1 469E carrier could be associated with increased susceptibility to end-stage knee OA.

Association of interleukin 1beta gene (+3953) polymorphism and severity of endometriosis in Turkish women

Endometriosis is regarded as a complex trait, in which genetic and environmental factors contribute to the disease phenotype. We investigated whether the interleukin (IL) 1beta (+3953) polymorphism is associated with the severity of endometriosis. Diagnosis of endometriosis was made on the basis of laparoscopic findings. Stage of endometriosis was determined according to the Revised American Fertility Society classification. 118 women were enrolled in the study. 78 women did not have endometriosis, 6 women had stage I, 3 had stage II, 13 had stage III and 18 had stage IV endometriosis. Polymerase Chain Reaction (PCR), Restriction Fragment Length Polymorphism (RFLP), and agarose gel electrophoresis techniques were used to determine the IL 1beta (+3953) genotype. Frequencies of the IL-1beta (+3953) genotypes in the control group were: CC, 0.397; TT, 0.115; CT, 0.487. Frequencies of the IL-1beta (+3953) genotypes in cases were: CC, 0.375; TT, 0.225; CT, 0.400. We found a 2.22 fold increase in TT genotype in the endometriosis group. However, the difference was not statistically significant (P > 0.05). We also observed an increase in the frequency of IL-1beta (+3953) T allele in the endometriosis group. However, the difference was not statistically significant. We also investigated the association between IL-1beta (+3953) polymorphism and the severity of endometriosis. The frequencies of CC+CT genotypes in stage I, III and IV endometriosis patients were 83.3, 84/6 and 72.2%, respectively; and TT genotypes were 16.7, 15.4 and 27.8%, respectively. We observed a statistically insignificant increase in TT genotype in stage IV endometriosis (P > 0.05). We suggest that IL-1beta (+3953) polymorphism is not associated with endometriosis in Turkish women.

Functional genetic polymorphisms and female reproductive disorders: part II--endometriosis

BACKGROUND

Endometriosis has a strong genetic component, and numerous genetic studies have been reported.

METHODS

We have systematically reviewed these studies and included 114 in our final selection.

RESULTS

We found no consistent evidence linking endometriosis with specific polymorphisms in genes encoding inflammatory mediators, proteins involved in sex steroid metabolism, vascular function and tissue remodelling. Although a number of polymorphisms have been associated with endometriosis in selected populations, the associations have not been independently confirmed, either because only single studies were carried out on these markers/genes or because other studies reported no association. The most solid evidence linking specific polymorphisms to endometriosis came from studies investigating glutathione-S-transferase, a phase II detoxification enzyme. Carriage of the GSTT1 null deletion variant showed consistent association with endometriosis with a 29% increased risk; however, it cannot be excluded that this result was due to publication bias, and this association should be independently confirmed in large-scale, well-designed case–control studies.

CONCLUSIONS

The evidence of an association between genetic polymorphisms and endometriosis is weak. Carriage of the GSTT1 null deletion may moderately increase the risk of this disease. We suggest that the methodology of association studies should be improved in order to identify and validate associations in endometriosis.