Autoantibodies to the IGF1 Receptor in Graves' Orbitopathy.
ABSTRACT Context:Graves' disease (GD) is maintained by stimulating antibodies against the TSH receptor. Graves' orbitopathy (GO) is the main extrathyroidal manifestation of GD, potentially involving autoimmunity against the IGF1 receptor (IGF1R).Objective:We tested for autoantibodies against the IGF1R (IGF1R-Abs) in sera of GD patients and controls and elucidated their possible implication in the disease.Design:A diagnostic assay for IGF1R-Ab was established with recombinant human IGF1R as autoantigen. Serum samples or purified Ig preparations were analyzed for IGF1R binding and modulation of IGF1 signaling in vitro. A total of 108 consecutive GO patients represented on average by 5.4 separate serum samples per individual along with 92 healthy controls were analyzed.Results:IGF1R-Ab were detected in 10 serum samples from control subjects (11%) and in 60 samples (10%) from the GO patient serum bank. The positive patient samples were derived from 15 individuals yielding an IGF1R-Ab prevalence of 14% in GO. More than three consecutive samples were available from 11 of the 15 positive GO patients spanning an average disease period of 2 years. IGF1R-Ab concentrations were constantly elevated in these patients demonstrating relatively stable IGF1R-Ab expression over time. IGF1R-Ab failed to stimulate IGF1R autophosphorylation but instead inhibited IGF1-induced signaling in hepatocarcinoma HepG2 cells. Similarly, growth of MCF7 breast cancer cells was inhibited by IGF1R-Ab, supporting their classification as IGF1 antagonists.Conclusions:Our data demonstrate the existence of IGF1R-Abs in humans but do not support the hypothesis that the IGF1R-Abs contribute to GO pathogenesis.
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ABSTRACT: Context: Rituximab depletes CD20(+) B cells and has shown potential benefit in thyroid associated ophthalmopathy (TAO). The impact of rituximab on T cell phenotype in TAO is unexplored. Objective: To quantify the abundance of IGF-1R(+) CD4 and CD8 T cells in active TAO before and after treatment with rituximab. Design: Retrospective case series assessing IGF-1R(+) T cells before and after treatment with rituximab with an 18 month follow-up. Setting: Tertiary care center. Patients: Study participants included 8 patients. Interventions: Two infusions of rituximab (1g or 500mg each) were administered two weeks apart. Main outcome measures: Quantification of IGF-1R(+) T cells using flow cytometry. Results: Eight patients with moderate to severe TAO (mean pretreatment clinical activity score (CAS) 5.1 ± 0.2 SEM) were treated. Four to 6 weeks following treatment, CAS improved to 1.5 ± 0.3 SEM, while the proportion of IGF-1R(+) CD3(+) T cells declined from 41.9% to 28.3% (p=0.004). The proportion of IGF-1R(+) CD4(+) and IGF-1R(+)CD8(+) T cells declined 4-6 weeks after treatment (from 45.6% to 21.5% and from 32.0% to 15.8%, p=0.003 and 0.001, respectively). In two patients, IGF-1R(+) CD4(+) and IGF-1R(+) CD8(+) subsets approximated pretreatment levels after 16 weeks. Conclusions: Increased frequency of IGF-1R(+) T cells in patients with TAO declines within 4-6 weeks following rituximab treatment. This phenotypic shift coincides with clinical improvement. Thus, assessment of the abundance of IGF-1R(+) T cells in response to rituximab may provide a biomarker of clinical response. Our current findings further implicate the IGF-1R pathway in the pathogenesis of TAO.The Journal of Clinical Endocrinology and Metabolism 03/2014; · 6.31 Impact Factor
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ABSTRACT: : The pathophysiology of thyroid eye disease (TED) is complex and incompletely understood. Orbital fibroblasts (OFs) seem to be the key effector cells that are responsible for the characteristic soft tissue enlargement seen in TED. They express potentially pathogenic autoantigens, such as thyrotropin receptor and insulin-like growth factor-1 receptor. An intricate interplay between these autoantigens and the autoantibodies found in Graves disease may lead to the activation of OFs, which then leads to increased hyaluronan production, proinflammatory cytokine synthesis, and enhanced differentiation into either myofibroblasts or adipocytes. Some of the OFs in TED patients seem to be derived from infiltrating fibrocytes. These cells originate from the bone marrow and exhibit both fibroblast and myeloid phenotype. In the TED orbit, they may mediate the orbital expansion and inflammatory infiltration. Last, lymphocytes and cytokines are intimately involved in the initiation, amplification, and maintenance of the autoimmune process in TED.Journal of neuro-ophthalmology: the official journal of the North American Neuro-Ophthalmology Society 06/2014; 34(2):177-85. · 1.09 Impact Factor
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ABSTRACT: Context: Graves' orbitopathy (GO) is caused by expansion of the orbital contents by excess adipogenesis and over-production of hyaluronan (HA). Immunosuppressive and anti-inflammatory treatments of GO are not always effective and can have side-effects, while targeting GO-associated tissue remodelling might be a more logical therapeutic strategy. Previously, we reported that signalling cascades through IGF1R and TSHR within orbital preadipocyte/fibroblasts drove adipogenesis and HA production. Our current study, combined stimulation of IGF1R and TSHR increase HA accumulation, which we hypothesize is by activation of PI3K1A/PI3K1B respectively. The central aim of this study was to investigate whether PI3K/mTORC1 inhibitors affected adipogenesis and/or HA production within orbital preadipocyte/fibroblasts. Methods: Human orbital preadipocytes were treated with/without inhibitors, LY294002 (PI3K-1A/mTORC1), AS-605240 (PI3K-1B) or PI103 (PI3K-1A/mTORC1) in serum-free medium for 24 h or cultured in adipogenic medium for 15 days. QPCR was used to measure HAS2 transcripts and the terminal adipogenesis differentiation marker LPL. HA accumulation in the medium was measured by ELISA. Results: Unlike AS-605240, both LY294002 (10 μM) and PI-103 (5 μM) significantly decreased HAS2 transcripts/HA-accumulation and adipogenesis. Since PI-103 and LY294002 are dual PI3K/mTOR inhibitors, we investigated inhibition of mTORC1 (rapamycin 100 nM), which significantly decreased adipogenesis but had no effect on HAS2 transcripts/HA, implicating PI3K-1A in the latter. Conclusions: Combined inhibition of PI3K-1A and mTORC1 signalling in vitro decreased both HA accumulation and adipogenesis. Since PI3K and mTOR inhibitors are clinically used to treat other conditions, they have potential to be repositioned to be used as an alternative non-immunosuppressive therapy of GO.The Journal of Clinical Endocrinology and Metabolism 04/2014; · 6.31 Impact Factor