Figures
Abstract
Background
Interleukin-16 (IL-16), a pleiotropic cytokine, plays a fundamental role in inflammatory diseases. This study investigates the association between IL-16 polymorphisms and the risk of knee osteoarthritis (OA) in a Chinese population.
Methods
The IL-16 rs11556218, rs4072111, and rs4778889 polymorphisms were determined in 150 knee OA cases and 147 healthy controls through polymerase chain reaction-restriction fragment length polymorphism.
Results
The results suggested that the variants in IL-16 gene rs11556218 site were associated with a decreased knee OA risk after adjusting for age, sex, BMI, and smoking and drinking status (TG vs. TT: OR, 0.69; 95% CI, 0.53–0.89; P = 0.006; GG vs. TT: OR, 0.64; 95% CI, 0.45–0.90; P = 0.042; dominant model: OR, 0.68; 95% CI, 0.29–0.87; P = 0.002; G vs. T allele: OR, 0.77; 95% CI, 0.66–0.90; P = 0.003). Similarly, subjects bearing the rs4072111 variant genotypes and alleles also had a lower susceptibility to knee OA compared with those bearing the wild-type (CT vs. CC: OR, 0.66; 95% CI, 0.53–0.83; P = 0.002; TT vs. CC: OR, 0.57; 95% CI, 0.40–0.82; P = 0.027; dominant model: OR, 0.65; 95%, CI 0.52–0.80; P <0.001; T vs. C allele: OR, 0.69; 95% CI, 0.58–0.81; P <0.001). Further, the C allele and the combined genotype (CC+CT) of rs4778889 were associated with a slightly decreased risk of knee OA. In addition, we found two high-risk haplotypes: TTT (OR, 3.70) and GCC (OR, 6.22). Finally, serum IL-16 levels of knee OA patients were significantly higher than those of controls (P = 0.001).
Citation: Luo S-X, Li S, Zhang X-H, Zhang J-J, Long G-H, Dong G-F, et al. (2015) Genetic Polymorphisms of Interleukin-16 and Risk of Knee Osteoarthritis. PLoS ONE 10(5): e0123442. https://doi.org/10.1371/journal.pone.0123442
Academic Editor: Tuan Van Nguyen, Garvan Institute of Medical Research, AUSTRALIA
Received: August 19, 2014; Accepted: March 3, 2015; Published: May 8, 2015
Copyright: © 2015 Luo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Data Availability: All relevant data are within the paper.
Funding: This research was supported by National Natural Science Foundation of China (No. 81460345); National Natural Science Youth Foundation of Guangxi (2012GXNSFBA053124); Health Department Self-raised Foundation of Guangxi (Z2011064). The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
Osteoarthritis (OA) of the knee, which affects about 10% of adults over 55 years old, is a common but complex disease characterized by the degradation of articular cartilage, often resulting in joint disability [1]. Although many risk factors have been associated with OA, including age, previous injury, obesity, diet, hormone therapy, and smoking habits [2–4], the pathogenesis of OA remains largely unknown and needs to be further elucidated.
Inflammatory processes and cytokines play essential roles in the pathogenesis of synovitis and cartilage destruction associated with OA [5, 6]. Variations in cytokine levels among individuals are a plausible explanation for differences in disease susceptibility and severity, and are principally attributable to single nucleotide polymorphisms (SNPs) in cytokine-encoding genes [7]. This relationship is particularly true for cytokine gene polymorphisms and OA; previous studies have investigated the relationship between a series of cytokines, such as interleukin (IL)-1 [8], IL-4 [9], IL-6 [7], IL-17 [10], IL-18 [11], and tumor necrosis factor-alpha (TNF-α) [12] gene polymorphisms, and the risk of developing OA. However, these genes can explain only a small part of the genetic component of this complex disease.
IL-16, as a pro-inflammatory cytokine whose functions include chemoattraction and modulation of T cell activation [13], is an important mediator in inflammatory and autoimmune diseases, as well as in tumor growth and progression [14, 15]. The IL-16 gene is located on chromosome 15q26.3 [16] and is initially translated into a precursor protein consisting of 631 amino acids, which is cleaved by caspase-3 to form the active C-terminal domain containing 121 amino acids [17, 18]. IL-16 is a CD4-specific ligand required for the initiation of CD4 bioactivity. Through binding to the CD4 molecule, IL-16 can selectively activate CD4+ T cells, monocytes, macrophages, eosinophils, and dendritic cells [19, 20]. In addition, IL-16 can increase the production of inflammatory cytokines, such as TNF-α, IL-1β, IL-6, and IL-15, leading to inflammatory response [21, 22]. Thus, it is biologically reasonable to hypothesize a potential relationship between IL-16 gene polymorphisms and knee OA risk.
Several IL-16 gene SNPs have been thoroughly investigated. A common SNP in IL-16 gene is rs4778889 T/C, located 295 bp upstream from the transcription start site and associated with altered levels of gene expression [23]. Another two SNPs, rs11556218 T/G and rs4072111 C/T, are located in an exon region, and their single-nucleotide changes would result in an amino acid substitution; the first results in an asparagine (Asn) to lysine (Lys) substitution in exon 6 of the IL-16 gene, and the second represents a serine (Ser) to proline (Pro) substitution. Several studies have recently revealed that IL-16 gene polymorphisms are associated with several human diseases, including gastric cancer [24], colorectal cancer [25], renal cell carcinoma [26], Graves’ disease [27], coronary heart disease [28], and ischemic stroke [29]. We have previously identified a significant association between the rs11556218 T/G polymorphism of the IL-16 gene and susceptibility to hepatocellular [30] and nasopharyngeal carcinoma [31] in a Chinese population.However, to date, there have been no reports on the relationship of IL-16 gene polymorphisms and knee OA. The aim of the present study was to analyze the association of IL-16 polymorphisms with knee OA susceptibility and the influence of SNPs on IL-16 serum levels in patients with knee OA versus healthy controls in a Chinese population.
Materials and Methods
Study subjects
This case-control study was approved by the ethics committee of the First Affiliated Hospital of Guangxi Medical University, China. All of the participants provided written informed consent.
A total of 150 patients diagnosed with primary knee OA and 147 healthy controls were consecutively selected from the First Affiliated Hospital of Guangxi Medical University and the Ninth Affiliated Hospital of Guangxi Medical University in Guangxi, China, between February 2011 and February 2013. Knee OA diagnosis was evaluated according to the American College of Rheumatology clinical criteria [32]. The following exclusion criteria were considered: rheumatoid arthritis, ankylosing spondylitis, septic arthritis, and other arthritis or any other systemic inflammatory or autoimmune disorders. Further, patients with a previous traumatic knee injury or any history of trauma were excluded from the study. An alcohol drinker was defined as someone who consumed alcoholic beverages at least once per week for more than 6 months. Subjects were considered smokers if they smoked up to 1 year before the date of diagnosis for cases, or up to the date of interview for controls.
The controls without clinical evidence of OA and any disease mentioned as exclusion criteria were randomly selected from a pool of healthy volunteers who visited the general health check-up centers at the same hospitals during the same time period for routine scheduled physical exams.
DNA extraction
Peripheral blood samples (2 mL) were collected from all of the subjects in ethylenediaminetetraacetic acid-coated vials and stored at—20°C until DNA extraction. Genomic DNA was extracted from white blood cell fractions using the phenol-chloroform extraction method. DNA concentration was determined spectrophotometrically.
Genotyping of the IL-16 genomic variants
The rs11556218, rs4072111, and rs4778889 polymorphism genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The primer sequences, reaction conditions, restriction enzymes used, and length of digestion products are listed in Table 1. To confirm the genotyping results, a total of 30 (10%) PCR-amplified DNA samples were randomly selected and genotyped by DNA sequencing with an ABI Prism 3100 (Applied Biosystems, Shanghai Sangon Biological Engineering Technology & Services Co., Ltd., China). The results were 100% concordant.
Serum IL-16 levels
Serum samples were available for all patients and healthy controls. Following blood sample collection, the serum was allowed to clot for 30 min at 4°C before centrifugation at 3,000 rpm for 10 min at 4°C. Total serum was isolated and stored at—20°C until further use. Serum IL-16 concentrations were detected using a sandwich ELISA with the same batch of reagents according to the manufacturer’s instructions. The minimum level of detection for IL-16 was 5 pg/mL. The intra-assay coefficients of variation were 10%.
Sample size consideration
We estimated the sample size using Quanto software (version 1. 2.4). We based on probability of α = 0.05 and β = 0.1 and assuming that the prevalence of the risk allele (rs11556218 G) in the control group was 40% [30], and estimated odds ratio (OR) was 0.5 Approximately 1 to 1 case–control ratio was chosen. According to the above parameters, estimated 134 sample size had enough power to assess the effect of IL-16 genetic polymorphisms on the risk of knee OA.
Statistical analysis
Student’s t-test (for continuous variables) or χ2 test (for categorical variables) were used to evaluate differences in the distributions of selected demographic variables, and frequencies of genotypes of IL-16 polymorphisms between cases and controls. Agreement with the Hardy-Weinberg equilibrium for each SNP was tested using a goodness-of-fit χ2 test. Genotype, allele, and haplotype distributions of IL-16 were compared among different groups using the χ2 test and Fisher’s exact test when appropriate. The Haploview software [33] was used to calculate the degree of pairwise linkage disequilibrium (LD) for each pair of SNPs as well as for haplotype analysis. We developed binary logistic regression models to estimate odds ratios (ORs) with corresponding 95% confidence intervals (CIs) to test the association of the various genotypes of interest and the risk of knee OA. All ORs were adjusted for age, gender, BMI, smoking and drinking state. Statistical significance was assumed at two-sided P values at <0.05 level. All of the statistical analyses were performed in the Statistical Package for Social Sciences (SPSS, version 13.0).
Results
Characteristics of the study population
Table 2 summarizes the characteristics of the 150 knee OA patients and 147 control subjects included in this study. The mean ages (SD) of the control group and knee OA group were 58.3 ± 9.6 and 59.5 ± 8.9 years, respectively. There were no significant differences for sex, mean age, BMI, smoking and drinking status between cases and control groups, suggesting that subjects matching based on these variables was adequate.
Genotype and allele distribution of IL-16 polymorphisms
The distribution of each allele and genotype is shown in Table 3. All three SNPs were within the Hardy-Weinberg equilibrium. For the rs11556218 polymorphism, there was a significant difference in the genotype and allele frequencies among knee OA patients and control subjects. The frequencies of the TT, TG, and GG genotypes of rs11556218 were 36.7%, 51.1%, and 12.2% in healthy controls, and 55.3%, 37.3%, and 7.4% in patients with knee OA, respectively. Binary logistic regression analyses adjusting for age, gender, BMI, smoking and drinking status showed that the TG and GG genotypes of rs11556218 were both associated with a statistically significant decreased risk of knee OA compared with the TT genotype (OR, 0.69; 95% CI, 0.53–0.89; p = 0.006 for TG genotype; OR, 0.64; 95% CI, 0.45–0.90; p = 0.042 for GG genotype). Under the dominant model, the combined genotypes GG + TG appeared to have lower susceptibility to OA (OR = 0.68, 95% CI 0.29–0.87, p = 0.002). The data also revealed that subjects with the G allele appeared to have a lower susceptibility to knee OA compared with those bearing the T allele (OR, 0.58; 95% CI, 0.41–0.82; p = 0.002).
Regarding the rs4072111 polymorphism, the frequencies of the CC, CT, and TT genotypes were 60.5%, 33.3%, and 6.1% for control subjects and 80%, 18%, and 2% in knee OA patients, respectively. The CT and TT genotypes were associated with a significantly decreased risk of knee OA compared with patients with the CC genotype (OR, 0.66; 95% CI, 0.53–0.83; p = 0.002 and OR, 0.57; 95% CI, 0.40–0.82; p = 0.027, respectively). The combined CC+TC genotypes were also associated with a significantly decreased risk of knee OA (OR, 79; 95% CI, 063–0.98; P = 0.045). Using the C allele as a reference, a significant correlation was detected between the presence of the T allele and a lower risk of developing knee OA (OR, 0.69; 95% CI, 0.58–0.81; p <0.001).
For genotype and allele frequencies of the IL-16 rs4778889 T/C polymorphisms, we found that subjects with the C allele and combined CC+TC genotypes (dominant model) appeared to have a slightly lower risk of knee OA compared with those bearing the T allele (OR, 0.68; 95% CI, 0.45–0.99; p = 0.044, and OR, 0.79; 95% CI, 0.63–0.98; P = 0.044, respectively).
Stratified analysis
When analyses of genotype and allele frequencies were stratified by gender, significant differences in the distributions of IL-16 polymorphisms among patients with knee OA and control groups were observed (Table 3). Women who carried the IL-16 (rs11556218 T/G) G allele had a significantly decreased risk of knee OA compared with those carrying the T allele (OR, 0.74; 95% CI, 0.60–0.91; p = 0.007). Similarly, women who carried the IL-16 (rs4072111 C/T) T allele showed a lower susceptibility to knee OA compared with those carrying the C allele (OR, 0.68; 95% CI, 0.55–0.85; p = 0.004). Men who carried the IL-16 (rs4072111 C/T) T allele showed a decreased risk of knee OA compared with those carrying the C allele (OR, 0.71; 95% CI, 0.55–0.92; p = 0.038), but no significant differences were found for the rs11556218 T/G polymorphism. Regarding the rs4778889 SNP, we found a significant difference of the genotype and allele frequencies between knee OA patients and controls in women, but not in men.
Haplotype analyses of IL-16 gene polymorphisms and knee OA risk
LD analyses were performed in knee OA patients and healthy controls using the Haploview ver.4.2 software. No statistically significant evidence of LD was observed among these three SNPs between knee OA patients and healthy controls (for rs11556218 and rs4072111, D’ = 0.22, r2 = 0.006; for rs4778889 and rs11556218, D’ = 0.59, r2 = 0.195; for rs4778889 and rs4072111, D’ = 0.64, r2 = 0.030). Further, haplotype analysis to evaluate the haplotype frequencies of polymorphisms located within the same chromosome regions was performed in order to derive haplotypes specifically correlated with knee OA. A total of seven haplotypes were derived from the observed genotypes. The haplotype distributions in knee OA patients and healthy controls are shown in Table 4. Two high-risk haplotypes were found: TTT (OR, 3.70; 95% CI, 1.57–8.72; p = 0.003) and GCC (OR, 6.22; 95% CI, 2.37–16.33; p = 0.0004). The remaining haplotypes were not associated with risk of knee OA.
Serum IL-16 levels and polymorphisms
The median serum concentration of IL-16 detected was 36.70 ± 6.72 pg/mL in healthy controls and 44.32 ± 8.78 pg/mL in knee OA patients (Table 2). The serum levels of IL-16 detected in knee OA patients were significantly higher than those in healthy control subjects (p = 0.001). However, when studying the relationship between the IL-16 polymorphisms present and IL-16 serum levels among patients with knee OA and healthy controls, no significant differences were observed.
Discussion
In the present study, we selected a common IL-16 SNP, namely rs4778889, located 295 bp upstream from the transcription start site and associated with altered levels of gene expression [23], as well as two other SNPs (rs11556218 and rs4072111), to evaluate their association in patients with knee OA and healthy controls. The latter two SNPs (rs11556218 and rs4072111) are located in an exon region, and their single-nucleotide changes would result in an amino acid substitution. To the best of our knowledge, this is the first study to investigate whether IL-16 gene polymorphisms are associated with the risk of knee OA and whether these correlate with serum levels of IL-16. The present results revealed that the IL-16 rs11556218 polymorphism, representing an Asn to Lys substitution in exon 6 of the IL-16 gene, has a significant effect on the risk of knee OA; individuals carrying the rs11556218 G allele had a significantly decreased risk of developing knee OA compared with those carrying the T allele (OR, 0.77; 95% CI, 0.66–0.90). In addition, the non-synonymous SNP, rs4072111 C/T, representing a Ser to Pro substitution, was associated with a significantly decreased risk of developing knee OA. Regarding the IL-16 rs4778889 T/C polymorphism, we found that subjects with the C allele appeared to have a slightly lower risk of knee OA compared with those bearing the T allele (OR, 0.83; 95% CI, 0.69–0.98). We further evaluated the effect of IL-16 polymorphisms on knee OA risk stratified by sex and found that the association appeared stronger in female patient subgroups.
Despite the positive relationship between rs11556218 and rs4072111 polymorphisms and the risk of knee OA observed in this study, IL-16 serum levels did not show any significant differences other than being cumulatively higher in patients with knee OA relative to healthy controls. In addition, we found two haplotypes (TTT and GCC) to be significantly associated with susceptibility to knee OA. Thus, the above data indicates that there is no association between IL-16 polymorphisms and IL-16 serum levels. However, the results also suggest that IL-16 gene polymorphisms may be significantly associated with the risk of knee OA. Although the sample size is not large enough, this is the first case-control study evaluating the association between IL-16 polymorphisms and the risk of knee OA.
Previous attempts have been made to identify genetic factors involved in knee OA using genome-wide association studies (GWAS). Recently, several OA susceptibility loci have been identified in GWAS with significance levels [34–40]. Among them, the DVWA gene (SNPs rs11718863 and rs7639618) and a region containing HLA class II/III genes (SNPs rs7775228 and rs10947262). However, this genome-wide significant association was shown in Asians but not in Europeans [34–36]. On the other hand, genome-wide significant loci were identified to have an association with knee OA in Europeans. These included the rs3815148 SNP in COG5 on chromosome 7q22 [37, 38], rs11842874 in MCF2L on chromosome 13 [40], and rs6976 in GNL3 on chromosome 3 [39]. To date, the IL-16 gene has not yet been identified through GWAS. In fact, recent GWAS in knee OA mainly focused on chromosome 3, chromosome 7, and chromosome 13 genes [34, 37–39]. The IL-16 gene is located on chromosome 15q26.3. IL-16 is a pleiotropic cytokine whose functions include chemoattraction and modulation of T cell activation [13] and is an important mediator in inflammatory and autoimmune diseases as well as in tumor growth and progression [14, 15]. In addition, IL-16 can activate the secretion of tumor-associated inflammatory cytokines, such as TNF-α, IL-1β, IL-6, and IL-15, all of which are major factors involved in tumorigenesis [21, 22]. In recent years, IL-16 gene polymorphisms have been associated with several human diseases, including gastric cancer [24], colorectal cancer [25], renal cell carcinoma [26], Graves’ disease [27], coronary heart disease [28, 41, 42], and ischemic stroke [29]. Our previous study has shown that the IL-16 rs11556218 T/G polymorphism was significantly associated with susceptibility to both hepatocellular [30] and nasopharyngeal carcinoma [31].
Pathologically, various inflammatory components are involved in OA. In OA, the increased synthetic and anti-inflammatory activity of chondrocytes loses out to the increased degradative activity [43, 44]. The increased synthetic activity is confined to the deeper cartilage layers, which allows the imbalance towards degradation to persist in the upper layer, near the synovial boundary. Ultimately, chondrocyte malfunction and apoptosis limit the response potential and hasten the progression of OA [43, 44]. Therefore, we postulated that IL-16 polymorphisms may modulate the susceptibility to OA.
In the current study, we found that patients carrying the G (rs11556218 T/G), T (rs4072111 C/T), and C (rs4778889 T/C) alleles were associated with a significantly decreased risk for knee OA compared to individuals carrying the wild-type alleles. This finding is consistent with our hypothesis, suggesting that IL-16 rs11556218, rs4072111, and rs4778889 polymorphisms may play an important role in the pathogenesis of knee OA. Further, we found that the association between IL-16 rs11556218 T/G and rs4778889 T/C polymorphisms and knee OA risk appeared stronger in female patients. Nevertheless, this evidence is suggestive but not conclusive, and was unexpected and difficult to explain. It is possible that this result is due to the larger number of female subjects (n = 205) compared to male subjects (n = 92), resulting in a limited statistical power and robustness. On the other hand, it might be attributed to the lower exposure to risk factors, such as tobacco smoking and heavy drinking, of female patients compared to males. Finally, this association might also be the result of estrogen-related effects; estrogen can interact with IL-16 and reduce the possibility of developing knee OA [45–47]. Nevertheless, since the sample size of the current study was relatively small, these findings need to be confirmed by further larger sample size studies which also investigate the underlying mechanisms of this association.
A haplotype is a set of SNPs on a single chromatid which are likely to be inherited together in a block pattern more frequently than expected by chance owing to the presence of linkage disequilibrium [48]. In the current study, we found that two haplotypes (TTT and GCC) of the IL-16 gene were significantly associated with the susceptibility to knee OA (OR, 3.70; 95% CI, 1.57–8.72 for the TTT haplotype and OR, 6.22; 95% CI, 2.37–16.33 for the GCC haplotype). We also evaluated the influence of IL-16 polymorphisms on IL-16 serum levels in patients with knee OA versus healthy controls, and found that the median serum level of IL-16 in patients was significantly higher than in controls. Our data suggest that a higher serum IL-16 level might serve as a risk factor for knee OA. However, the serum levels of IL-16 detected in groups of patients with different genotypes did not show any significant differences, probably due to the relatively small sample size; further confirmation would be provided by additional patient data.
Several potential limitations of this study must be acknowledged. First, our patient sample size was relatively small and therefore the study’s statistical power may have been limited. Thus, additional studies with larger samples are desirable. Second, the study population was limited to the Guangxi population and therefore the findings may not be generalized to other populations. Continued study of the role of IL-16 polymorphisms in patient susceptibility to knee OA from other ethnic populations would also be of great value. Finally, the current research studied only three SNPs in the IL-16 gene. It would be interesting to identify more SNPs and study their association with knee OA.
In conclusion, the present study showed that functional polymorphisms of IL-16 are associated with the risk of knee OA. We found that the variant alleles rs11556218 T/G, rs4072111C/T, and rs4778889 T/C were associated with a decreased risk of knee OA compared with wild-type alleles. These findings suggest that the IL-16 rs11556218 T/G, rs4072111 C/T, and rs4778889 T/C polymorphisms might be markers for genetic susceptibility to knee OA. Furthermore, serum IL-16 levels were significantly associated with increased risk of knee OA. These findings, after validation by larger studies, might help identify at-risk populations for primary knee OA prevention.
Author Contributions
Conceived and designed the experiments: JMZ XQ. Performed the experiments: SXL SL XHZ JJZ. Analyzed the data: SXL YL XHZ GHL. Contributed reagents/materials/analysis tools: GFD WS YD YL. Wrote the paper: YL SXL.
References
- 1. Scott D, Kowalczyk A. Osteoarthritis of the knee. Am Fam Physician. 2008;77: 1149–1150. pmid:18481563
- 2. Sowers M. Epidemiology of risk factors for osteoarthritis: systemic factors. Curr Opin Rheumatol. 2001;13: 447–451. pmid:11604603
- 3. Bierma-Zeinstra SM, Koes BW. Risk factors and prognostic factors of hip and knee osteoarthritis. Nat Clin Pract Rheumatol. 2007;3: 78–85. pmid:17299445
- 4. Jiang L, Tian W, Wang Y, Rong J, Bao C, Liu Y, et al. Body mass index and susceptibility to knee osteoarthritis: a systematic review and meta-analysis. Joint Bone Spine. 2012;79: 291–297. pmid:21803633
- 5.
Goldring SR, Goldring MB. The role of cytokines in cartilage matrix degeneration in osteoarthritis. Clin Orthop Relat Res. 2004: S27–36.
- 6. Brooks P. Inflammation as an important feature of osteoarthritis. Bulletin of the World Health Organization. 2003;81: 689–690. pmid:14710513
- 7. Honsawek S, Deepaisarnsakul B, Tanavalee A, Yuktanandana P, Bumrungpanichthaworn P, Malila S, et al. Association of the IL-6 -174G/C gene polymorphism with knee osteoarthritis in a Thai population. Genet Mol Res. 2011;10: 1674–1680. pmid:21863560
- 8. Kaarvatn MH, Jotanovic Z, Mihelic R, Etokebe GE, Mulac-Jericevic B, Tijanic T, et al. Associations of the interleukin-1 gene locus polymorphisms with risk to hip and knee osteoarthritis: gender and subpopulation differences. Scand J Immunol. 2013;77: 151–161. pmid:23216199
- 9. Yigit S, Inanir A, Tekcan A, Tural E, Ozturk GT, Kismali G, et al. Significant association of interleukin-4 gene intron 3 VNTR polymorphism with susceptibility to knee osteoarthritis. Gene. 2014;537: 6–9. pmid:24406619
- 10. Han L, Lee HS, Yoon JH, Choi WS, Park YG, Nam SW, et al. Association of IL-17A and IL-17F single nucleotide polymorphisms with susceptibility to osteoarthritis in a Korean population. Gene. 2014;533: 119–122. pmid:24096234
- 11. Hulin-Curtis SL, Bidwell JL, Perry MJ. Evaluation of IL18 and IL18R1 polymorphisms: genetic susceptibility to knee osteoarthritis. Int J Immunogenet. 2012;39: 106–109. pmid:22136483
- 12. Ji B, Shi J, Cheng X, Zhou J, Zhou Q, Cao C, et al. Association analysis of two candidate polymorphisms in the tumour necrosis factor-alpha gene with osteoarthritis in a Chinese population. Int Orthop. 2013;37: 2061–2063. pmid:23748461
- 13. Smith AJP, Humphries SE. Cytokine and cytokine receptor gene polymorphisms and their functionality. Cytokine & Growth Factor Reviews. 2009;20: 43–59.
- 14. Moss SF, Blaser MJ. Mechanisms of disease: Inflammation and the origins of cancer. Nat Clin Pract Oncol. 2005;2: 90–97; quiz 91 p following 113. pmid:16264881
- 15. Lu H, Ouyang W, Huang C. Inflammation, a key event in cancer development. Mol Cancer Res. 2006;4: 221–233. pmid:16603636
- 16. Kim HS. Assignment of human interleukin 16 (IL16) to chromosome 15q26.3 by radiation hybrid mapping. Cytogenet Cell Genet. 1999;84: 93. pmid:10343113
- 17. Baier M, Bannert N, Werner A, Lang K, Kurth R. Molecular cloning, sequence, expression, and processing of the interleukin 16 precursor. Proc Natl Acad Sci U S A. 1997;94: 5273–5277. pmid:9144227
- 18. Zhang Y, Center DM, Wu DM, Cruikshank WW, Yuan J, Andrews DW, et al. Processing and activation of pro-interleukin-16 by caspase-3. J Biol Chem. 1998;273: 1144–1149. pmid:9422780
- 19. Cruikshank WW, Center DM, Nisar N, Wu M, Natke B, Theodore AC, et al. Molecular and functional analysis of a lymphocyte chemoattractant factor: association of biologic function with CD4 expression. Proc Natl Acad Sci U S A. 1994;91: 5109–5113. pmid:7910967
- 20. Center DM, Kornfeld H, Cruikshank WW. Interleukin 16 and its function as a CD4 ligand. Immunol Today. 1996;17: 476–481. pmid:8908813
- 21. Kai H, Kitadai Y, Kodama M, Cho S, Kuroda T, Ito M, et al. Involvement of proinflammatory cytokines IL-1beta and IL-6 in progression of human gastric carcinoma. Anticancer Res. 2005;25: 709–713. pmid:15868900
- 22. Shanmugham LN, Petrarca C, Frydas S, Donelan J, Castellani ML, Boucher W, et al. IL-15 an immunoregulatory and anti-cancer cytokine. Recent advances. J Exp Clin Cancer Res. 2006;25: 529–536. pmid:17310844
- 23. Nakayama EE, Wasi C, Ajisawa A, Iwamoto A, Shioda T. A new polymorphism in the promoter region of the human interleukin-16 (IL-16) gene. Genes Immun. 2000;1: 293–294. pmid:11196708
- 24. Zhang T, Wang H. Variants of interleukin-16 associated with gastric cancer risk. Asian Pac J Cancer Prev. 2013;14: 5269–5273. pmid:24175812
- 25. Azimzadeh P, Romani S, Mohebbi SR, Kazemian S, Vahedi M, Almasi S, et al. Interleukin-16 (IL-16) gene polymorphisms in Iranian patients with colorectal cancer. J Gastrointestin Liver Dis. 2011;20: 371–376. pmid:22187702
- 26. Zhu J, Qin C, Yan F, Wang M, Ding Q, Zhang Z, et al. IL-16 polymorphism and risk of renal cell carcinoma: association in a Chinese population. Int J Urol. 2010;17: 700–707. pmid:20529140
- 27. Tsai KH, Chang CY, Tsai FJ, Lin HJ, Yang YS, Lim YP, et al. Association of interleukin-16 polymorphisms with graves' disease in a taiwanese population. Chin J Physiol. 2014;57: 69–75. pmid:24694201
- 28. Tong Z, Li Q, Zhang J, Wei Y, Miao G, Yang X. Association between interleukin 6 and interleukin 16 gene polymorphisms and coronary heart disease risk in a Chinese population. J Int Med Res. 2013;41: 1049–1056. pmid:23881440
- 29. Liu XL, Du JZ, Zhou YM, Shu QF, Li YG. Interleukin-16 polymorphism is associated with an increased risk of ischemic stroke. Mediators Inflamm. 2013;2013: 564750. pmid:24288444
- 30. Li S, Deng Y, Chen ZP, Huang S, Liao XC, Lin LW, et al. Genetic polymorphism of interleukin-16 influences susceptibility to HBV-related hepatocellular carcinoma in a Chinese population. Infect Genet Evol. 2011;11: 2083–2088. pmid:22019522
- 31. Qin X, Peng Q, Lao X, Chen Z, Lu Y, Lao X, et al. The association of interleukin-16 gene polymorphisms with IL-16 serum levels and risk of nasopharyngeal carcinoma in a Chinese population. Tumour Biol. 2014;35: 1917–1924. pmid:24101193
- 32. Altman R, Asch E, Bloch D, Bole G, Borenstein D, Brandt K, et al. Development of criteria for the classification and reporting of osteoarthritis. Classification of osteoarthritis of the knee. Diagnostic and Therapeutic Criteria Committee of the American Rheumatism Association. Arthritis Rheum. 1986;29: 1039–1049. pmid:3741515
- 33. Barrett JC, Fry B, Maller J, Daly MJ. Haploview: analysis and visualization of LD and haplotype maps. Bioinformatics. 2005;21: 263–265. pmid:15297300
- 34. Miyamoto Y, Shi D, Nakajima M, Ozaki K, Sudo A, Kotani A, et al. Common variants in DVWA on chromosome 3p24.3 are associated with susceptibility to knee osteoarthritis. Nat Genet. 2008;40: 994–998. pmid:18622395
- 35. Nakajima M, Takahashi A, Kou I, Rodriguez-Fontenla C, Gomez-Reino JJ, Furuichi T, et al. New sequence variants in HLA class II/III region associated with susceptibility to knee osteoarthritis identified by genome-wide association study. PLoS One. 2010;5: e9723. pmid:20305777
- 36. Meulenbelt I, Chapman K, Dieguez-Gonzalez R, Shi DQ, Tsezou A, Dai J, et al. Large replication study and meta-analyses of DVWA as an osteoarthritis susceptibility locus in European and Asian populations. Human Molecular Genetics. 2009;18: 1518–1523. pmid:19181678
- 37. Kerkhof HJ, Lories RJ, Meulenbelt I, Jonsdottir I, Valdes AM, Arp P, et al. A genome-wide association study identifies an osteoarthritis susceptibility locus on chromosome 7q22. Arthritis Rheum. 2010;62: 499–510. pmid:20112360
- 38. Evangelou E, Valdes AM, Kerkhof HJ, Styrkarsdottir U, Zhu Y, Meulenbelt I, et al. Meta-analysis of genome-wide association studies confirms a susceptibility locus for knee osteoarthritis on chromosome 7q22. Ann Rheum Dis. 2011;70: 349–355. pmid:21068099
- 39. Zeggini E, Panoutsopoulou K, Southam L, Rayner NW, Day-Williams AG, Lopes MC, et al. Identification of new susceptibility loci for osteoarthritis (arcOGEN): a genome-wide association study. Lancet. 2012;380: 815–823. pmid:22763110
- 40. Day-Williams AG, Southam L, Panoutsopoulou K, Rayner NW, Esko T, Estrada K, et al. A variant in MCF2L is associated with osteoarthritis. Am J Hum Genet. 2011;89: 446–450. pmid:21871595
- 41. Huang H, Zeng Z, Zhang L, Liu R, Li X, Qiang O, et al. The association of interleukin-16 gene polymorphisms with susceptibility of coronary artery disease. Clin Biochem. 2013;46: 241–244. pmid:23195133
- 42. Hai-Feng T, Wei W, Yuan-Yuan Y, Jun Z, Su-Ping G, Hui-Ming L. Association between Polymorphisms in IL-16 Genes and Coronary Heart Disease risk. Pak J Med Sci. 2013;29: 1033–1037. pmid:24353682
- 43. Sandell LJ, Aigner T. Articular cartilage and changes in arthritis. An introduction: cell biology of osteoarthritis. Arthritis Res. 2001;3: 107–113. pmid:11178118
- 44. Pelletier JP, Martel-Pelletier J, Abramson SB. Osteoarthritis, an inflammatory disease: potential implication for the selection of new therapeutic targets. Arthritis Rheum. 2001;44: 1237–1247. pmid:11407681
- 45. Linn S, Murtaugh B, Casey E. Role of sex hormones in the development of osteoarthritis. PM R. 2012;4: S169–173. pmid:22632696
- 46. Jochems C, Islander U, Erlandsson M, Engdahl C, Lagerquist M, Gjertsson I, et al. Role of endogenous and exogenous female sex hormones in arthritis and osteoporosis development in B10.Q-ncf1*/* mice with collagen-induced chronic arthritis. BMC Musculoskelet Disord. 2010;11: 284. pmid:21159208
- 47. Ma HL, Blanchet TJ, Peluso D, Hopkins B, Morris EA, Glasson SS. Osteoarthritis severity is sex dependent in a surgical mouse model. Osteoarthritis and Cartilage. 2007;15: 695–700. pmid:17207643
- 48. Seng KC, Seng CK. The success of the genome-wide association approach: a brief story of a long struggle. Eur J Hum Genet. 2008;16: 554–564. pmid:18285837