Investigation of rheumatoid arthritis susceptibility genes identifies association of AFF3 and CD226 variants with response to anti-tumour necrosis factor treatment.

BACKGROUND: Anti-tumour necrosis factor (anti-TNF) therapy has proved to be highly successful in treating rheumatoid arthritis (RA), although 30-40% of patients have little or no response. The authors hypothesise that this may be genetically determined. In other complex diseases, susceptibility genes have been shown to influence treatment response. The aim of the current study was to investigate the association of markers within confirmed RA susceptibility loci with the response to anti-TNF treatment. METHODS: Eighteen single nucleotide polymorphisms (SNPs) mapping to 11 genetic loci were genotyped in 1012 patients with RA receiving treatment with etanercept, infliximab or adalimumab. Multivariate linear regression analyses were performed using the absolute change in 28 joint count disease activity score (DAS28) between baseline and 6-month follow-up as the outcome variable, adjusting for confounders. p Values <0.05 were considered statistically significant and associated markers were genotyped in an additional 322 samples. Analysis was performed in the combined cohort of 1334 subjects with RA treated with anti-TNF. RESULTS: In the combined analysis, SNPs mapping to AFF3 and CD226 had a statistically significant association with the response to anti-TNF treatment under an additive model. The G allele at rs10865035, mapping to AFF3, was associated with an improved response to anti-TNF treatment (coefficient -0.14 (95% CI -0.25 to -0.03), p=0.015). At the CD226 SNP rs763361, the C allele conferred reduced response to treatment (coefficient 0.11 (95% CI 0.00 to 0.22), p=0.048). CONCLUSION: These results suggest that AFF3 and CD226, two confirmed RA susceptibility genes, have an additional role in influencing the response to anti-TNF treatment.

Polymorphisms spanning the TNFR2 and TACE genes do not contribute towards variable anti-TNF treatment response.

The introduction of tumour necrosis factor antagonists (anti-TNF) has greatly improved the treatment of rheumatoid arthritis, however, a significant proportion of patients fail to respond to therapy. We hypothesized that variants spanning the type 2 TNF receptor (TNFR2) and the TNF cleavage enzyme (TACE) genes contribute towards the observed variation in patient response (defined as the absolute change in 28-joint count disease activity score). Twenty-nine single nucleotide polymorphisms (SNPs) were genotyped in a large cohort of patients (n=602) and analysed by multivariate linear regression. Three SNPs (rs520916, rs652625, rs597519) mapping upstream of TNFR2 showed borderline evidence for association (P<0.1) across the complete cohort and, more so, in the etanercept-treated subgroup. However, the evidence of association was neither replicated in an independent cohort (n=377) nor strengthened after combined analysis (n=979). We conclude that common SNPs spanning the TNFR2 and TNF cleavage enzyme (TACE) genes do not have a major effect on the response to anti-TNF therapy in rheumatoid arthritis patients.

PADI4 genotype is not associated with rheumatoid arthritis in a large UK Caucasian population.

BACKGROUND: Polymorphisms of the peptidylarginine deiminase type 4 (PADI4) gene confer susceptibility to rheumatoid arthritis (RA) in East Asian people. However, studies in European populations have produced conflicting results. This study explored the association of the PADI4 genotype with RA in a large UK Caucasian population. METHODS: The PADI4_94 (rs2240340) single nucleotide polymorphism (SNP) was directly genotyped in a cohort of unrelated UK Caucasian patients with RA (n=3732) and population controls (n=3039). Imputed data from the Wellcome Trust Case Control Consortium (WTCCC) was used to investigate the association of PADI4_94 with RA in an independent group of RA cases (n=1859) and controls (n=10 599). A further 56 SNPs spanning the PADI4 gene were investigated for association with RA using data from the WTCCC study. RESULTS: The PADI4_94 genotype was not associated with RA in either the present cohort or the WTCCC cohort. Combined analysis of all the cases of RA (n=5591) and controls (n=13 638) gave an overall OR of 1.01 (95% CI 0.96 to 1.05, p=0.72). No association with anti-CCP antibodies and no interaction with either shared epitope or PTPN22 was detected. No evidence for association with RA was identified for any of the PADI4 SNPs investigated. Meta-analysis of previously published studies and our data confirmed no significant association between the PADI4_94 genotype and RA in people of European descent (OR 1.06, 95% CI 0.99 to 1.13, p=0.12). CONCLUSION: In the largest study performed to date, the PADI4 genotype was not a significant risk factor for RA in people of European ancestry, in contrast to Asian populations.

Biologic therapy for rheumatoid arthritis: clinical efficacy and predictors of response.

Rheumatoid arthritis (RA) is a chronic, disabling disease of the synovial joints, thought to be autoimmune in origin. The emergence of biologic therapies has proven to be highly successful in effectively treating RA in the majority of cases. However, the cost of these agents is high and some patients do not respond to these drugs, or they suffer from adverse events. This article will review the currently available data on efficacy and the clinical, genetic, and biomarkers of response to these biologic therapies in RA. The anti-tumour necrosis factor-alpha (anti-TNFalpha) agents, adalimumab, etanercept and infliximab, act to neutralize the pro-inflammatory cytokine. Response to these agents is higher in patients receiving concurrent disease modifying anti-rheumatic drugs or non-steroidal anti-inflammatory drugs, in those with lesser disability, and in non-smokers. Many genetic predictors of response have been investigated, such as the shared epitope, the TNF gene and its receptors, but none have been absolutely confirmed. Synovial expression of TNFalpha has been suggested as a biomarker of response, while anti-cyclic citrullinated peptide antibody and rheumatoid factor (RF)-positivity predict poor response. Newer biologic agents include the interleukin (IL)-1 receptor antagonist anakinra, the B-cell depleting agent rituximab, the selective costimulation modulator abatacept, and the anti-IL-6 receptor monoclonal antibody tocilizumab. No genetic studies of response to these agents have been performed to date. However, it has been reported that low synovial infiltration of B cells and complete B-cell depletion after the first rituximab infusion are predictors of good response to this agent.

Combined effects of three independent SNPs greatly increase the risk estimate for RA at 6q23.

The most consistent finding derived from the WTCCC GWAS for rheumatoid arthritis (RA) was association to a SNP at 6q23. We performed a fine-mapping of the region in order to search the 6q23 region for additional disease variants. 3962 RA patients and 3531 healthy controls were included in the study. We found 18 SNPs associated with RA. The SNP showing the strongest association was rs6920220 [P = 2.6 x 10(-6), OR (95% CI) 1.22 (1.13-1.33)]. The next most strongly associated SNP was rs13207033 [P = 0.0001, OR (95% CI) 0.86 (0.8-0.93)] which was perfectly correlated with rs10499194, a SNP previously associated with RA in a US/European series. Additionally, we found a number of new potential RA markers, including rs5029937, located in the intron 2 of TNFAIP3. Of the 18 associated SNPs, three polymorphisms, rs6920220, rs13207033 and rs5029937, remained significant after conditional logistic regression analysis. The combination of the carriage of both risk alleles of rs6920220 and rs5029937 together with the absence of the protective allele of rs13207033 was strongly associated with RA when compared with carriage of none [OR of 1.86 (95% CI) (1.51-2.29)]. This equates to an effect size of 1.50 (95% CI 1.21-1.85) compared with controls and is higher than that obtained for any SNP individually. This is the first study to show that the confirmed loci from the GWA studies, that confer only a modest effect size, could harbour a significantly greater effect once the effect of additional risk variants are accounted for.

Investigation of genetic variants within candidate genes of the TNFRSF1B signalling pathway on the response to anti-TNF agents in a UK cohort of rheumatoid arthritis patients.

The introduction of anti-tumour necrosis factor (TNF) agents has greatly improved the treatment of rheumatoid arthritis; however, a significant proportion of patients fail to respond to therapy. We hypothesized that genes within the TNF receptor superfamily member 1B signalling pathway contribute towards the observed variation in patient response. This was tested by genotyping 73 single-nucleotide polymorphisms (SNPs) from six candidate genes (DUSP1, HRB, IKBKAP, MAP3K1, MAP3K14 and TANK) in a large UK cohort of rheumatoid arthritis patients (n=642). Two SNPs [rs96844 (MAP3K1) and rs4792847 (MAP3K14)] showed evidence of association (P<0.05) to treatment response and were subsequently examined in an independent cohort of patients (n=428). Replication of association to either SNP was not achieved, but combined analysis of the complete cohort (n=1070) provided nominal evidence of association to both SNPs. We conclude that analysis of the common variation in the selected candidate genes did not provide strong evidence to implicate their involvement in varying patient response to anti-TNF treatment.

Rheumatoid arthritis susceptibility loci at chromosomes 10p15, 12q13 and 22q13.

The WTCCC study identified 49 SNPs putatively associated with rheumatoid arthritis at P = 1 x 10(-4) - 1 x 10(-5) (tier 3). Here we show that three of these SNPs, mapping to chromosome 10p15 (rs4750316), 12q13 (rs1678542) and 22q13 (rs3218253), are also associated (trend P = 4 x 10(-5), P = 4 x 10(-4) and P = 4 x 10(-4), respectively) in a validation study of 4,106 individuals with rheumatoid arthritis and an expanded reference group of 11,238 subjects, confirming them as true susceptibility loci in individuals of European ancestry.