FCGR2A Polymorphisms Research Articles

No association between C-reactive protein gene polymorphisms and decrease of C-reactive protein serum concentration after infliximab treatment in Crohn's disease

We recently showed an association between the FCGR3A V/F polymorphism and the biological response [assessed on the basis of a C-reactive protein (CRP) concentration decrease] to infliximab in Crohn's disease. The CRP and FCGR3A genes are located on the same 1q23 locus. The present study aimed: (i) to exclude a linkage disequilibrium (LD) between the two genes and (ii) to study the association between CRP polymorphisms and the response to infliximab, particularly the decrease in CRP after treatment, in Crohn's disease patients. FCGR3A (V/F) polymorphism and three CRP polymorphisms (-717G/A, 1444C/T, CRP 4A/G) were determined in 206 healthy blood donors and 189 Crohn's disease patients who had received infliximab for either refractory luminal or fistulizing Crohn's disease. Clinical response was defined as complete, partial or absent according to the same definition as in controlled trials. The biological response was defined on the basis of CRP decrease. There was no LD between CRP and FCGR3A in healthy donors or Crohn's disease patients. CRP polymorphisms had no impact on CRP decrease after infliximab. The proportions of Crohn's disease having a positive clinical or biological response were not statistically different among the various genotypes of CRP polymorphisms. There was no LD between CRP and FCGR3A polymorphisms. CRP polymorphisms were not associated with the response to infliximab in Crohn's disease.

Association of FCGR2A and FCGR2A-FCGR3A haplotypes with susceptibility to giant cell arteritis

The Fc gamma receptors have been shown to play important roles in the initiation and regulation of many immunological and inflammatory processes and to amplify and refine the immune response to an infection. We have investigated the hypothesis that polymorphism within the FCGR genetic locus is associated with giant cell arteritis (GCA). Biallelic polymorphisms in FCGR2A, FCGR3A, FCGR3B and FCGR2B were examined for association with biopsy-proven GCA (n = 85) and healthy ethnically matched controls (n = 132) in a well-characterised cohort from Lugo, Spain. Haplotype frequencies and linkage disequilibrium (D') were estimated across the FCGR locus and a model-free analysis performed to determine association with GCA. There was a significant association between FCGR2A-131RR homozygosity (odds ratio (OR) 2.10, 95% confidence interval (CI) 1.12 to 3.77, P = 0.02, compared with all others) and carriage of FCGR3A-158F (OR 3.09, 95% CI 1.10 to 8.64, P = 0.03, compared with non-carriers) with susceptibility to GCA. FCGR haplotypes were examined to refine the extent of the association. The haplotype showing the strongest association with GCA susceptibility was the FCGR2A-FCGR3A 131R-158F haplotype (OR 2.84, P = 0.01 for homozygotes compared with all others). There was evidence of a multiplicative joint effect between homozygosity for FCGR2A-131R and HLA-DRB1*04 positivity, consistent with both of these two genetic factors contributing to the risk of disease. The risk of GCA in HLA-DRB1*04 positive individuals homozygous for the FCGR2A-131R allele is increased almost six-fold compared with those with other FCGR2A genotypes who are HLA-DRB1*04 negative. We have demonstrated that FCGR2A may contribute to the 'susceptibility' of GCA in this Spanish population. The increased association observed with a FCGR2A-FCGR3A haplotype suggests the presence of additional genetic polymorphisms in linkage disequilibrium with this haplotype that may contribute to disease susceptibility. These findings may ultimately provide new insights into disease pathogenesis.

Analysis of Fcγ receptor haplotypes in rheumatoid arthritis: FCGR3A remains a major susceptibility gene at this locus, with an additional contribution from FCGR3B

The Fcγ receptors play important roles in the initiation and regulation of many immunological and inflammatory processes, and genetic variants (FCGR) have been associated with numerous autoimmune and infectious diseases. The data in rheumatoid arthritis (RA) are conflicting and we previously demonstrated an association between FCGR3A and RA. In view of the close molecular proximity with FCGR2A, FCGR2B and FCGR3B, additional polymorphisms within these genes and FCGR haplotypes were examined to refine the extent of association with RA. Biallelic polymorphisms in FCGR2A, FCGR2B and FCGR3B were examined for association with RA in two well characterized UK Caucasian and North Indian/Pakistani cohorts, in which FCGR3A genotyping had previously been undertaken. Haplotype frequencies and linkage disequilibrium were estimated across the FCGR locus and a model-free analysis was performed to determine association with RA. This was followed by regression analysis, allowing for phase uncertainty, to identify the particular haplotype(s) that influences disease risk. Our results reveal that FCGR2A, FCGR2B and FCGR3B were not associated with RA. The haplotype with the strongest association with RA susceptibility was the FCGR3A–FCGR3B 158V-NA2 haplotype (odds ratio 3.18, 95% confidence interval 1.13–8.92 [P = 0.03] for homozygotes compared with all genotypes). The association was stronger in the presence of nodules (odds ratio 5.03, 95% confidence interval 1.44–17.56; P = 0.01). This haplotype was also more common in North Indian/Pakistani RA patients than in control individuals, but not significantly so. Logistic regression analyses suggested that FCGR3A remained the most significant gene at this locus. The increased association with an FCGR3A–FCGR3B haplotype suggests that other polymorphic variants within FCGR3A or FCGR3B, or in linkage disequilibrium with this haplotype, may additionally contribute to disease pathogenesis.

Long term efficacy of rituximab in follicular lymphoma (FL) and polymorphism in IgG Fc receptor FcγRIIIa/FcγRIIa genes

6598 Background: FCGR3A coding for the FcγRIIIa receptor displays a functional dimorphism (FCGR3A-158V/F) and human IgG1 have a higher affinity for FCGR3A-158VV NK cells and increased ADCC compared to FCGR3A-158FF NK cells (Dall’Ozzo et al. 2004). We and others have previously demonstrated that FCGR3A-158VV genotype was associated with a higher rate of clinical and molecular response to rituximab in 49 patients receiving rituximab (anti-CD20 chimeric IgG1) alone for previously untreated low-tumor burden FL (Cartron et al. 2002). We have recently reported (Solal-Celigny et al. 2004) that 28% of all these patients and 34% of responders remain free of relapse more than 5 years after treatment. Weng et al. (2003) have also reported that FCGR2A-131HH patients have a better response and PFS after treatment by rituximab. The aim of this study was to determine the influence of FCGR3A and FCGR2A polymorphisms on the clinical outcome in the long-term responders. Methods: The FCGR3A and FCGR2A genotypes were determined by a nested PCR (PCR-ASRED) in the 49 patients who have been treated with rituximab (375 mg/m2 x 4) for FL. Results: FCGR3A-158VV patients represented 20% of the population, FCGR3A-158FF 35% and heterozygous patients 45% (FCGR3A-158F carriers). FCGR2A-131HH patients represented 20% of the population, FCGR2A-131RR 31% and heterozygous patients 49% (FCGR2A-131R carriers). The median PFS was 18 months for the whole population and was 25 months and 16 months for FCGR3A-158VV and FCGR3A-158F carriers patients (log-rank test, p = 0.8), and 23 months and 16 months for FCGR2A-131HH and FCGR2A-131R carriers, respectively (log-rank test, p = 0.7). Among, the 14 patients free of relapse more than 5 years after rituximab treatment, 2 (15%) and 12 (85%) were FCGR3A-158VV (p = 0.7) and FCGR3A-158F carriers, and 3 (20%) and 11 (80%) were FCGR2A-131HH and FCGR2A-131R carriers, respectively (p = 1.0). Conclusions: After a long term follow-up, neither FCGR3A-158VV nor FCGR2A-131HH genotype are significantly associated with a longer PFS, despite the fact that FCGR3A-158V homozygosity is associated with a higher rate of clinical and molecular response to rituximab in low-tumor burden FL patients. No significant financial relationships to disclose.

FCGR3A and FCGR2A polymorphisms may not correlate with response to alemtuzumab in chronic lymphocytic leukemia

AbstractThe in vivo mechanism of action of alemtuzumab (anti-CD52; Campath-1H) remains unclear. With rituximab, FCGR3A and FCGR2A high-affinity polymorphisms have been associated with clinical response in lymphoma but not in CLL, suggesting potential divergent mechanisms of action between these 2 diseases. Herein, we examined FCGR3A (V/V, n = 4; V/F, n = 10; F/F, n = 19) and FCGR2A (A/A, n = 5; H/A, n = 22; H/H, n = 6) polymorphisms in 36 patients with relapsed CLL who were treated with thrice-weekly alemtuzumab for 12 weeks to assess the potential influence these high-affinity FcγR receptor polymorphisms had on response to alemtuzumab. Response to alemtuzumab was similar regardless of FCGR3A polymorphism (V/V, 25%; V/F, 40%; F/F, 32%) or FCGR2A polymorphism (A/A, 40%; H/A, 32%; H/H, 33%). These findings indicate that FCGR3A and FCGR2A polymorphisms may not predict response to alemtuzumab in CLL. Future studies examining larger cohorts of alemtuzumab-treated patients with CLL will be required to definitively determine the predictive value of specific FCGR polymorphisms to treatment response. (Blood. 2005;105:289-291)

Rituximab-dependent cytotoxicity by natural killer cells: influence of FCGR3A polymorphism on the concentration-effect relationship.

The FCGR3A gene dimorphism generates two allotypes: FcgammaRIIIa-158V and FcgammaRIIIa-158F. The genotype homozygous for FcgammaRIIIa-158V (VV) is associated with higher clinical response to rituximab, a chimeric anti-CD20 IgG1 used in the treatment of B lymphoproliferative malignancies. Our objective was to determine whether this genetic association relates to rituximab-dependent cytotoxicity mediated by FcgammaRIIIa/CD16a+ cells. The number of CD16+ circulating monocytes, T cells, and natural killer (NK) cells in 54 donors was first shown to be unrelated to FCGR3A polymorphism. We then demonstrated that FcgammaRIIIa-158V displays higher affinity for rituximab than FcgammaRIIIa-158F by comparing rituximab concentrations inhibiting the binding of 3G8 mAb (anti-CD16) with VV NK cells and NK cells homozygous for FcgammaRIIIa-158F (FF). VV and FF NK cells killed Daudi cells similarly after FcgammaRIIIa engagement by saturating concentrations of rituximab or 3G8. However, the rituximab concentration resulting in 50% lysis (EC(50)) observed with NK cells from VV donors was 4.2 times lower than that observed with NK cells from FF donors (on average 0.00096 and 0.00402 microg/ml, respectively, P = 0.0043). Finally, the functional difference between VV and FF NK cells was restricted to rituximab concentrations weakly sensitizing CD20. This study supports the conclusion that FCGR3A genotype is associated with response to rituximab because it affects the relationship between rituximab concentration and NK cell-mediated lysis of CD20+ cells. Rituximab administration could therefore be adjusted according to FCGR3A genotype.

A promoter haplotype of the immunoreceptor tyrosine-based inhibitory motif-bearing FcgammaRIIb alters receptor expression and associates with autoimmunity. I. Regulatory FCGR2B polymorphisms and their association with systemic lupus erythematosus.

FcgammaRIIb, the immunoreceptor tyrosine-based inhibitory motif-containing receptor for IgG (Mendelian Inheritance in Man no. 604590), plays an important role in maintaining the homeostasis of immune responses. We have identified 10 novel single-nucleotide polymorphisms in the promoter region of human FCGR2B gene and characterized two functionally distinct haplotypes in its proximal promoter. In luciferase reporter assays, the less frequent promoter haplotype leads to increased expression of the reporter gene in both B lymphoid and myeloid cell lines under constitutive and stimulated conditions. Four independent genome-wide scans support linkage of the human FcgammaR region to the systemic lupus erythematosus (SLE; Online Mendelian Inheritance in Man no. 152700) phenotype. Our case-control study in 600 Caucasians indicates a significant association of the less frequent FCGR2B promoter haplotype with the SLE phenotype (odds ratio = 1.65; p = 0.0054). The FCGR2B haplotype has no linkage disequilibrium with previously identified FCGR2A and FCGR3A polymorphisms, and after adjustment for FCGR2A and FCGR3A, FCGR2B showed a persistent association with SLE (odds ratio = 1.72; p = 0.0083). These results suggest that an expression variant of FCGR2B is a risk factor for human lupus and implicate FCGR2B in disease pathogenesis.

Pharmacogenetics in cancer treatment.

Interindividual variability in the efficacy and toxicity of drug therapy is associated with polymorphisms in genes encoding drug-metabolizing enzymes, transporters, or drug targets. Pharmacogenetics aims to identify individuals predisposed to high risk of toxicity from conventional doses of cancer chemotherapeutic agents. We review the role of genetic polymorphisms in UGT1A1 and TPMT, as well as mutations in DPD, in influencing drug disposition and toxicity. Recent studies show that pharmacogenetic determinants may also influence treatment outcomes. We discuss the clinical significance of polymorphisms in TS, MTHFR, and FCGR3A, as well as the polymorphic DNA repair genes XPD and XRCC1, in influencing response to chemotherapy and survival outcomes. Finally, the potential implications of transporter pharmacogenetics in influencing drug bioavailability are addressed.