Allelic variants of XRCC1 and XRCC3 repair genes and susceptibility of oral cancer in Brazilian patients

J Oral Pathol Med (2013) 42 : 180–185 Background: The capacity for DNA repair is essential in maintaining cellular functions and homeostasis; however, this capacity can be altered based on DNA sequence variations in DNA repair genes, which may contribute to the onset of cancer. Many single‐nucleotide polymorphisms (SNPs) in repair genes have been found to be associated with oral cancer. The aim of this study was to investigate the relationship between the presence of allelic variants Arg194Trp (rs:1799782) and Arg399Gln (rs: 25487) of XRCC1 gene and Thr241Met (rs: 861539) of XRCC3 gene and susceptibility to oral cancer. We also attempted to correlate the frequencies obtained for each of the SNPs to histopathological parameters. Methods: A case–control study was conducted with genomic DNA from 150 patients with oral squamous cell carcinomas and 150 controls. SNPs were genotyped by RFLP‐PCR. Results: The presence of the polymorphic variants of the XRCC1 gene within codon 194 (OR 0.82, 95% CI: 0.44–1.51) and codon 399 (OR 0.94, 95% CI: 0.59–1.50) and within the XRCC3 gene (OR 0.72; 95% CI: 0.45–1.16) were not associated with an increased risk of oral cancer. A combinational analysis of SNPs in both genes indicated no association. The presence of the allelic variants of these two genes had no statistically significant effect on tumor differentiation, lymph node invasion or tumor size. Conclusions: These results suggest that allelic variants of XRCC1 and XRCC3 are not suitable markers for susceptibility to carcinomas of the oral cavity and are also not related to the later stages of such tumors.     

TLR2, TLR3, TLR4 and CD14 gene polymorphisms associated with oral lichen planus risk

The aim of this study was to assess whether polymorphisms in toll‐like receptor (TLR) and cluster of differentiation 14 (CD14) genes are associated with oral lichen planus (OLP) risk and clinical course of the disease. The study group consisted of 101 patients with confirmed OLP and 104 healthy blood donors without systemic or oral mucosal diseases. Single nucleotide polymorphisms of TLR2 (rs3804099), TLR3 (rs3775291 and rs5743312), TLR4 (rs4986790 and rs4986791), and CD14 (rs2569190) genes were genotyped using real‐time PCR or PCR‐restriction fragment length polymorphism (PCR‐RFLP). The rs5743312 TLR3 gene polymorphism was associated with increased OLP risk in comparison with the wild type genotype (OR = 15.984, P = 0.011). No association with OLP risk was observed for the polymorphisms studied in TLR2, TLR4 and CD14 genes or for the rs3775291 polymorphism of the TLR3 gene. The polymorphisms of the TLR3 gene were in linkage disequilibrium (D′ = 1, r² = 0.1). Identified haplotypes were not associated with the risk of OLP. The findings of the current study suggest that the TT genotype of the rs5743312 TLR3 gene polymorphism may play a significant role in the aetiology of OLP.     

Single nucleotide polymorphisms of complement component 5 and periodontitis

Chai L, Song Y‐Q, Zee K‐Y, Leung WK. Single nucleotide polymorphisms of complement component 5 and periodontitis. J Periodont Res 2010; 45: 301–308. © 2009 John Wiley & Sons A/S Background and Objective: Polymorphisms of host defence genes might increase one’s risks for periodontitis. This study investigated whether tagging single nucleotide polymorphisms (SNPs) of the gene encoding complement component 5 (C5) are associated with periodontitis in a Hong Kong Chinese population. Material and Methods: Eleven tagging SNPs of 229 patients with at least moderate periodontitis and 207 control subjects without periodontitis were genotyped using an i‐plexGOLD MassARRAY mass‐spectrometry system. Results: Genotype AG of SNP rs17611 was more prevalent in the group of periodontitis patients than in the controls (54.6% vs. 41.7%, p = 0.007). The haplotype CGCA of the haplotype block consisting of rs1035029, rs17611, rs25681 and rs992670 was significantly associated with periodontitis in a dominant model (p = 0.001). The SNP rs17611 showed high linkage disequilibrium with rs1035029, rs25681 and rs992670. Smoking was also significantly associated with periodontitis (p = 0.006). Conclusion: The tagging SNP rs17611 of the C5 gene and smoking may be associated with periodontitis among the Hong Kong Chinese population.     

白介素12A基因多态性与OLP的相关性研究

目的：研究华东地区汉族人群IL-12A基因多态性与口腔扁平苔藓（orallichenplanus,OLP）的相关性。方法：采用TaqMan荧光定量PCR法检测华东地区292例OLP患者及686例正常对照者的IL-12A基因的5个SNP位点（rs3024415,rs2243123,rs583911,rs568408和rs2243143）,分析IL-12A基因多态性与OLP的相关性。结果：①华东地区健康人群IL-12A基因3′-UTRrs568408位点AA、GA和GG基因型频率分别是0．7％、12．4％和86．8％,而OLP患者分别是1．1％、18．4％和80．5％,其中GA和AA基因型分布频率显著高于正常对照组@=O．0427）。②正常对照组IL-12A基因rs583911位点AA、GA和GG基因型频率分别是4．2％、38．6％和57．1％,而OLP患者分别是9．5％、36．5％和54％,其中AA基因型分布频率显著高于对照组（p=O．00805）。③糜烂型OLP组IL-12A—rs568408／A等位基因频率显著高于正常对照组,分别为11．6％和6．94％（OR=I．76,95％CI：1．133—2,732,P=0．011）。结论：华东地区汉族OLP人群IL-12A基因rs568408位点存在多态性变异,可能与OLP的疾病易感性和严重程度有关。     

Determination of NLRP3 (rs4612666) and IL-1B (rs1143634) genetic polymorphisms in periodontally diseased and healthy subjects

ObjectiveThe focus of the current study was to identify if a possible association between NLRP3 (rs4612666) and IL-1B (rs1143634) single-nucleotide polymorphisms (SNPs) may be implicated in the etiopathogenesis of chronic periodontitis (CP) in a Colombian population.DesignOne hundred and twenty-four CP subjects and 81 periodontally healthy controls (HC) were recruited. Periodontal status was assessed by criteria based on probing depth, clinical attachment level, extent, and severity of periodontal breakdown. Human genomic DNA was obtained from saliva samples of the study subjects. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to identify the NLRP3 (rs4612666) and IL-1B (rs1143634) SNPs. The association of polymorphisms with CP was assessed individually and adjusted for confounding using a multivariate binary logistic regression model.ResultsBivariate analysis showed a weak association between CT genotype of NLRP3 (rs4612666) SNP and CP, however after logistic regression analysis, neither NLRP3 (rs4612666) nor IL-1B (rs1143634) polymorphisms were strongly/independently associated with disease status. Even so, an interaction effect was significantly detected not only among CT/CC genotypes of NLRP3 gene regarding to the age stratum ≥48 years, but also between CC genotype of the same gene and smoking habit.ConclusionAlthough the present results do not support that IL-1B (rs1143634) SNP could be identified as a risk predictor for CP in the present population, the synergistic interaction of the CT/CC genotypes of NLRP3 (rs4612666) SNP with ageing and/or smoking habit potentially might play a significant role in the pathogenic pathways of periodontal disease.     

MicroRNA‐137 promoter methylation in oral lichen planus and oral squamous cell carcinoma

Oral lichen planus (OLP) is a common oral mucosal disease, which is generally considered a potentially malignant lesion. To identify efficiently prognostic biomarker, we investigated the microRNA‐137 (miR‐137) promoter methylation in OLP and compared with the samples from healthy volunteers and patients with oral squamous cell carcinoma (OSCC). A total of 20 OLP and 12 patients with OSCC as well as 10 healthy subjects were subjected to miR‐137 promoter methylation analysis using methylation‐specific PCR (MSP). To address the malignancy prediction potential from miR‐137 promoter methylation status, methylation of the p16 gene, a well‐known tumor suppressor, was investigated in the same samples. The p16 methylation and miR‐137 promoter methylation were found to be 25% and 35% in patients with OLP, 50% and 58.3% in patients with OSCC, and 0% and 0% in healthy subjects, respectively. The differences between miR‐137 and p16 methylation levels were statistically significant between healthy controls and patients. Methylation levels of the two promoters were also influenced by age, gender, and lesion duration. Interestingly, aberrant promoter methylation of the p16 and miR‐137 genes was only found in the epithelium but not in the connective tissue from patients with OLP. This raises the possibility to use miR‐137 methylation as a biomarker for malignant prediction in patients with OLP.     

Assessment of 14 functional gene polymorphisms in Japanese patients with oral lichen planus: a pilot case-control study

Oral lichen planus (OLP) is a refractory mucosal disease. Its pathogenesis is thought to involve immunologic and genetic alterations. To gain a better understanding of the genetic risk factors, the authors evaluated associations between 14 functional gene polymorphisms and OLP. 32 Japanese patients with OLP and 99 unrelated healthy Japanese controls were genotyped for 14 single nucleotide polymorphisms (SNPs) of genes that regulate host immune responses. Genotyping was performed with a modified version of the serial invasive signal amplification reaction. A trend towards over-representation of tumor necrosis factor receptor 2 (TNFR2) +587 G allele was found in the patients compared with the controls (allele frequency: P = 0.049). The other 13 SNPs were unassociated with OLP. These results suggest that TNFR2 +587 gene polymorphism may be associated with susceptibility to OLP.     

Genetic variation of IRF6 and TGFA genes in an HIV‐exposed newborn with non‐syndromic cleft lip palate

We present here the first reported case of a non‐syndromic cleft lip and palate (NSCLP) in an HIV‐exposed newborn of a mother on antiretroviral therapy (ART) in Indonesia. Genetic testing was performed to confirm a suspected genetic condition. Genomic DNA was extracted from the blood, and genetic variations of the interferon regulatory factor 6 (IRF6) rs642961 (Mspl) (G>A) and transforming growth factor alpha (TGFA) BamHI (rs11466297, A>C) and RsaI (rs3732248, C>T) were performed by PCR‐RFLP and IRF6 gene analysis by PCR sequencing. Genotyping of DNA sequence variants in the IRF6 gene showed both parents had genotype GA, while the child had genotype GG (genotype wild type). There was no difference observed in the TGFA BamHI gene variant between the child and her mother and father that were wild‐type polymorphisms (normal), while the Rsa1 polymorphisms of them were heterozygotes. A genetic variant of IRF6 might be a protective factor for NSCLP, while Rsa1 gene variant (A) allele can be considered to be the risk factor associated with NSCLP development. This case report also highlights the possible etiologic role of ART in NSCLP; therefore, early control of adverse effects of ART might be an important factor in decreasing the incidence of the congenital anomalies in HIV‐infected children.     

Mannose-binding lectin gene (MBL-2) polymorphism in oral lichen planus

TNF-α may be associated with the etiopathogenesis of oral lichen planus (OLP), and it has been suggested that polymorphism of mannose-binding lectin (MBL) increases the in vitro production of TNF- α. The aim of the present study was to assess the relevance of genetic diversity of MBL in OLP. The study sample comprised 90 individuals, 45 OLP patients and 45 healthy volunteers. MBL-2 gene was amplified using real-time PCR. Frequency of A/A genotype was 55.6% in OLP and 53.3% in healthy volunteers. Likewise, A/0 heterozygote genotype was found in 42.2% and 35.6%; 2.2% and 11.1%, had the recessive 0/0 genotype respectively. Frequencies of the “A” and “0” alleles were 77% and 23% in the OLP group and 71.2% in control group. There were no statistically significant differences regarding genotype frequency (p = 0.546) or allele frequency (p = 0.497). In conclusion, no significant association was found between polymorphism of MBL-2 gene and OLP.     

Functional variants of IL4 and IL6 genes and risk of tobacco-related oral carcinoma in high-risk Asian Indians

Oral Diseases (2011) 17 , 720–726 Background: Tobacco‐related oral squamous cell carcinoma (OSCC) is one of the most common cancers involving Indian males. We assessed the association of IL4 promoter –589 T>C, –33 T>C, and IL6–174 G>C functional genetic polymorphisms with tobacco‐related OSCC in Asian Indians. Patients and Methods: The IL4 and IL6 promoter polymorphisms were assessed in 140 patients with OSCC and 120 normal subjects by PCR–RFLP technique, and significance of the data was determined using chi‐square test. Results: The frequency of TC, CC genotype, and C allele at IL4 promoter sites –589 and –33 were higher in patients when compared with controls. Consequently, TC/CC genotypes and C allele at both sites appeared as susceptible. However, IL6–174 G>C single‐nucleotide polymorphisms (SNP) appeared to be protective in patients with OSCC. Of eight haplotypes, five were associated with two‐ to seven‐fold increased risk of tobacco‐related OSCC. These SNPs further showed heterogeneity among different ethnic population, but their distribution in Asian Indians stand closer to other Asian populations. Conclusions: In this study, IL4–589 CC, –33 CC genotype, and *C allele at both sites appeared to be susceptible, while IL6–174 CC genotype and *C allele appeared to be protective in patients with OSCC; hence, these SNPs may be a potential prognostic markers for tobacco‐related OSCC in Asian Indians.     

IRF6 gene variants in Central European patients with non‐syndromic cleft lip with or without cleft palate

Variants in the interferon regulatory factor 6 (IRF6) gene have repeatedly been associated with non‐syndromic cleft lip with or without cleft palate (NSCL/P). A recent study has suggested that the functionally relevant variant rs642961 is the underlying cause of the observed associations. We genotyped rs642961 in our Central European case–control sample of 460 NSCL/P patients and 952 controls. In order to investigate whether other IRF6 variants contribute independently to the etiology of NSCL/P, we also genotyped the non‐synonymous coding variant V274I (rs2235371) and five IRF6‐haplotype tagging single nucleotide polymorphisms (SNPs). A highly significant result was observed for rs642961 (P = 1.44 × 10^?6) in our sample. The odds ratio was 1.75 [95% confidence interval (CI): 1.38–2.22] for the heterozygous genotype and 1.94 (95% CI: 1.21–3.10) for the homozygous genotype, values that are similar to those reported in a previously published family‐based study. Our results thus confirm the involvement of the IRF6 variant, rs642961, in the etiology of NSCL/P in the Central European population. We also found evidence suggestive of an independent protective effect of the coding variant V274I. In order to understand fully the genetic architecture of the IRF6 locus, it will be necessary to conduct additional SNP‐based and resequencing studies using large samples of patients.     

Tumour necrosis factor‐alpha gene polymorphisms and susceptibility to oral lichen planus

Oral Diseases (2011) 17 , 206–209 Objective: This study is aimed to investigate the association between OLP susceptibility and clinical type in the Thai population and three polymorphisms within the promoter region of the TNF‐α at positions ‐863, ‐308 and ‐238 which have putative functional significances. Materials and Methods: Genomic DNA from 75 Thai patients with OLP and 154 healthy controls were genotyped for TNF‐α polymorphisms – ‐863(rs1800630), ‐308(rs1800629), and ‐238(rs361525) – using polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP). Results: We found a higher proportion of TNF‐alpha‐308 AA genotype (high producer genotype) among OLP patients (5/75; 6.67%) when compared to healthy controls (1/154; 0.65%; OR = 10.93; 95% CI = 1.21–251.9). For other polymorphisms (‐863 and ‐238), we did not find any significant association with OLP development; this was also the case with haplotype analysis (‐863/‐308/‐238). Conclusion: TNF‐α‐308AA may play a relevant role in the susceptibility and severity of OLP in the Thai population. However, further investigation of this study is needed.     

Revisiting the metallothionein genes polymorphisms and the risk of oral squamous cell carcinoma in a Brazilian population

Background Metallothioneins (MTs) gene polymorphisms have been associated with the ability of free radical scavenging and detoxification of heavy metals leading to cancer development. Our aim was to revisit, in a Brazilian population, single-nucleotide polymorphisms (SNPs) of the MT gene family previously associated with oral squamous cell carcinoma (OSCC). Material and Methods A case-control investigation with 28 OSCC patients and 45 controls was conducted, using conventional risk factors (tobacco use and alcohol consumption) as covariates. SNPs genotyping for rs8052334 (MT1B), rs964372 (MT1B), and rs1610216 (MT2A) was performed by PCR-RFLP, and SNPs for rs11076161 (MT1A) were analyzed by TaqMan assay. Results The only SNP associated with increased risk for OSCC was the MT-1A AA genotype (OR = 4.7; p = 0.01). We have also evidenced for the first time a significant linkage disequilibrium between the SNPs of MT-2A and MT-1A in this population with the highest frequency (30%) of the unfavorable haplotype G/A/C/T (rs1610216 / rs11076161 / rs964372 / rs8052334) of MT gene polymorphisms (OR = 6.2; p = 0.04). Interestingly, after removing the effects of conventional risk factors, we have uncovered the significance of the AA genotype of the rs11076161 with increased odds of 19-fold higher towards OSCC development. Conclusions This is the first demonstration that a significant linkage disequilibrium among gene polymorphisms of the MT family may affect susceptibility to oral cancer, which is conditioned by the G/A/C/T haplotype (rs1610216/rs11076161/rs964372/ rs8052334) and the MT-1A gene polymorphism has a potential clinical utility for the OSCC risk assessment. Key words:Oral squamous cell carcinoma, polymorphism, metallothionein, oral cancer.     

Prevalence of Candida spp., xerostomia,and hyposalivation in oral lichen planus – A controlled study

Objective

To determine the frequency of Candida spp., xerostomia, and salivary flow rate (SFR) in three different groups: patients with OLP (OLP group), patients with oral mucosal lesions other than OLP (non‐OLP group), and subjects without oral mucosal lesions (control group).

Material and methods

Xerostomia as well as SFR was investigated in the three groups. Samples for isolation of Candida spp. were collected from OLP lesions (38 patients), non‐OLP lesions (28 patients), and healthy subjects (32 subjects).

Results

There was no statistically significant difference regarding the frequency of xerostomia and hyposalivation among the three groups (P > 0.05). A higher prevalence for colonization by Candida spp. was found in the healthy subject as compared to that of patients with OLP (P = 0.03) and non‐OLP (P = 0.02) groups. Low SFR was not a factor for colonization by Candida spp.

Conclusions

Xerostomia and hyposalivation occur with similar frequency in subjects with and without oral lesions; also, the presence of oral lesions does not increase the susceptibility to colonization by Candida spp. It seems that any study implicating Candida spp. in the malignant transformation of oral lesions should be carried out mostly on a biochemical basis, that is, by testing the capability of Candida spp. to produce carcinogenic enzyme.     

Homozygote C/C at rs12543318 was risk factor for non‐syndromic cleft lip only from Western Han Chinese population

Non‐syndromic cleft lip with or without cleft palate (NSCL/P) is a complex disorder, and it results from both of the genetic modifiers and environmental factors, with genetic modifiers contributes to it more than environmental factors. GWASs made great progress in identifying the candidate genes for NSCL/P, but the findings need to be replicated in other populations. In this study, we selected eleven SNPs from recent GWASs and GWAS meta‐analysis to investigate their associations among 308 NSCL/P trios (134 non‐syndromic cleft lip only (NSCLO) trios and 174 non‐syndromic cleft lip with cleft palate (NSCLP) trios) from Han Chinese population. All SNPs were genotyped using SNPscan method and analyzed the data with FBAT, PLINK, and R package. Allelic TDT analysis showed that allele A at rs12543318 was associated with NSCLO trios (P = .0032, OR = 0.57, 95% CI: 0.39‐0.83), and parent‐of‐origin effect analysis indicated that allele A at rs12543318 was significantly maternally undertransmitted among NSCLO (P = .0046), which implied the potential influence of genomic imprinting; global TDT further confirmed this association. Individual genotypic TDT showed homozygote C/C at rs12543318 was overtransmitted among NSCLO (Z = 3.79, P = .00015) and NSCL/P groups (Z = 3.83, P = .00013), which indicated that it could increase the risk to have cleft babies. Our findings indicated that rs12543318 was associated with NSCLO from Western Han Chinese population, which will give new scientific evidence for later researches in the etiology of NSOCs.     

Single nucleotide polymorphisms of the vascular endothelial growth factor gene associated with incidence of oral squamous cell carcinoma

J Oral Pathol Med (2010) 39 : 786–792 Background: Vascular endothelial growth factor (VEGF) plays an important role in promoting angiogenesis and is overexpressed in several malignancies. Polymorphisms of the VEGF gene can alter VEGF protein expression, which may be biologically significant and account for heterogeneity in disease risk and outcome. The aim of this case–control study was to evaluate potential associations between single nucleotide polymorphisms (SNP) of the VEGF gene with susceptibility of oral squamous cell carcinoma (OSCC). Patients and methods: Five VEGF SNP (?1154 G/A, +405 G/C, +936 C/T, ?2578 C/A and ?460 C/T) were determined in peripheral blood isolated from 80 patients with OSCC and from 40 age‐ and gender‐matched healthy volunteers (RT‐PCR). Results: The +936 T allele and the ?2578 C/A SNP were expressed significantly more often in the OSCC‐group (P = 0.002; P < 0.0001) where three associations between two SNPs (+936 and +405, ?2578 and ?1154, ?460 and ?2578) were found. Conclusion: Our findings provide support that +936 T allele and ?2578 C/A SNP of the VEGF gene alone or in combination with other SNP are associated with OSCC. The SNPs may be used as biomarker for the development of specialized anti‐VEGF drugs. Further studies must confirm the value of preoperative genetic analysis for prognosis.     

Association of ENAM gene single nucleotide polymorphisms with dental caries in Polish children

Objectives

The objective of this study was to prove the association between dental caries and single nucleotide polymorphisms (SNPs) in the ENAM gene.

Material and methods

The research was carried out in 96 children (48 with caries and 48 counterparts free of this disease), aged 20–42 months, with 11–20 erupted teeth. All children were from four day nurseries located in Poznan. The study included the dental examination to select individuals to the research and oral swab collection for molecular evaluation. Seven selected SNPs markers of the ENAM gene were genotyped, five using TaqMan probe assay (rs2609428, rs7671281, rs36064169, rs3796704, and rs12640848) and two by Sanger sequencing (rs144929717 and rs139228330).

Results

Statistically significant higher prevalence of the alternative G allele and the alternative GG homozygote in the control group in comparison with the caries group in SNP rs12640848 was observed, respectively, p = 0.0062 and 0.0010. Although the prevalence of the AG heterozygote was higher for the caries subjects in comparison with controls (OR = 2.9), and the result was statistically significant (p = 0.0010), the overall prevalence of the G allele for this SNP was significantly higher in control group (OR = 2.3; p = 0.0062).

Conclusions

The study revealed the strong association between rs12640848 marker of ENAM gene and caries susceptibility in primary teeth in children from Poznan.

Clinical relevance

The presence of SNPs in the ENAM gene may be important as suspected predictive factor of dental caries occurrence in children.

     

Association of interleukin-1 gene polymorphisms with early-onset periodontitis

Background, aims: Early onset periodontal diseases (EOP) are a group of inflammatory disorders characterised by a rapid rate of periodontal tissue destruction, in young individuals who are otherwise healthy. There is now substantial evidence to suggest that genetic factors play a rôle in the pathogenesis of EOP but the precise nature of these factors remains unclear. Polymorphisms in cytokine genes which may underpin inter‐individual differences in cytokine synthesis and secretion have been associated with other diseases which have an inflammatory pathogenesis, including chronic adult periodontal disease (CAPD). Method: We therefore investigated the frequency of polymorphisms in the genes encoding interleukin‐1β (IL‐1β) and its receptor antagonist (IL‐1RA) in 70 EOP patients, including a subgroup of 21 localised EOP (L‐EOP) patients and 72 periodontally healthy controls. All subjects were of Caucasian heritage and systemically healthy. A single nucleotide polymorphism (SNP) in exon 5 of the IL‐1β gene (IL‐1β⁺³⁹⁵³) was analysed by amplifying the polymorphic region using PCR, followed by restriction digestion with Taq1 and gel electrophoresis. Results: The frequency of IL‐1β genotypes homozygous for allele 1 (corresponding to the presence of a restriction site) of the IL‐1β⁺³⁹⁵³ SNP was found to be significantly increased in EOP patients (χ² test, p=0.025). Upon stratification for smoking status a significant difference was found in the IL‐1β genotype distribution between EOP smokers compared to control smokers (F‐exact test, p=0.02), but not between EOP non‐smokers and control non‐smokers. The IL‐1β 1/1 genotype occurred at a higher frequency in EOP smokers (odds ratio=4.9) compared to control smokers. A variable number tandem repeat polymorphism (VNTR) in intron 2 of the IL‐1RA gene was analysed by amplifying the polymorphic region using PCR and fragment size analysis by gel electrophoresis. There was no evidence for an association of an IL‐1RA genotype with EOP. However the combination of IL‐1β allele 1 and IL‐1RA allele 1 (corresponding to 4 repeats) was associated with EOP (Clump, p=0.01). Conclusions: These findings suggest that an IL‐1β genotype in combination with smoking, and a combined IL‐1β and IL‐1RA genotype are risk factors for EOP and support a role for genetic and environmental factors in susceptibility to EOP.