Op0210 bruton’s Tyrosine Kinase (Btk) Is a Novel Independent Biomarker of Lymphoma in Primary Sjögren’s Syndrome: Data From 346 Patients of the Assess Cohort

Abstract

BackgroundPrimary Sjögren’s syndrome (pSS) is a B-cell driven systemic auto-immune disease associated with the highest risk of lymphoma among systemic auto-immune diseases. In the prospective ASSESS cohort (395 patients enrolled, with a 10-year follow-up), transcriptomic analysis recently showed the association between baseline peripheral blood overexpression of Bruton’s tyrosine kinase (BTK) and lymphoma.ObjectivesThis study aimed to confirm the transcriptomic findings at the mRNA and protein level and to evaluate the relevance of BTK as a lymphoma predictor with regards to other predictors.MethodsBTK mRNA expression was assessed using qRTPCR in whole blood samples from 63 patients (12 patients with a history of lymphoma, 9 patients with incident lymphoma occurring during the 10-year follow-up, 21 patients without lymphoma and no risk factors for lymphoma and 21 patients without lymphoma and ESSDAI ≥ 5). BTK protein expression in peripheral blood was analyzed by flow cytometry in 7 healthy controls, 5 pSS patients without risk factors for lymphoma, 8 pSS patients with ESSDAI ≥5, and 6 pSS patients with lymphoma. In 346 patients of the ASSESS cohort for whom all data were available, the association between pSS-related lymphoma and BTK expression at enrolment, with 9 validated lymphoma predictors (parotid enlargement, purpura, ESSDAI ≥ 5, lymphocytopenia, CD4/CD8 ratio ≤ 0.8, RF positivity, cryoglobulinemia, monoclonal component, and low C4) and other potential biomarkers (serum FLT3L, BAFF, digital interferon alpha, gammaglobulins, IgG, beta2microglobulin, kappa and lambda free light chains, quantitative levels of anti-SSA/SSB) was analyzed. Multivariate analyses took into account in a first model, BTK and the 9 validated predictors of pSS-related lymphoma, and in a second model variables associated with lymphoma in univariate analysis selected by a stepwise procedure.ResultsIn qRTPCR, BTK was significantly upregulated between pSS patients with and without lymphoma. In flow cytometry, BTK protein expression in CD19+B cells (p=0.03), and in most B-cell subpopulations, was significantly increased in patients with lymphoma compared to healthy controls. A gradual increase was observed in BTK expression of CD19+B cells, between patients without risk factors for lymphoma, those with ESSDAI ≥5, and those with lymphoma. In multivariate analysis, taking into account 9 validated predictors of lymphoma in pSS, BTK expression at enrolment was significantly associated with lymphoma (adjusted OR [aOR] 1.45; 95% CI [1.19-1.82]; p<0.001), along with CD4/CD8 ratio ≤ 0.8 (aOR 6.03; 95% CI [1.23-26.13]; p=0.02). In a second model including 4 biomarkers selected by a stepwise procedure, BTK expression remained significantly associated with lymphoma (aOR 1.36; 95% CI [1.14-1.64]; p<0. 001), as well as serum BAFF levels (mean [SD]:1028.5 pg/ml [710.3]; per 1000 BAFF units, aOR 2.04; 95% CI [1.3-3.19]; p=0.001), low C4 (aOR 4.16; 95% CI [1.43-13.88]; p=0.01) and CD4/CD8 ratio ≤0.8 (aOR 10.62; 95% CI [2.49-44.15]; p=0.001).ConclusionThese results confirm that increased expression of BTK in peripheral blood is associated with pSS-related lymphoma. These results also show the potential interest of combining B-cell (BTK and BAFF) and T-cell (CD4/CD8 ratio)-related biomarkers to evaluate the risk of lymphoma in pSS.AcknowledgementsTo the patients for their participation to the ASSESS cohort; To the investigators of the ASSESS cohort; plateforme de transcriptomique de l’Institut Cochin; centre de ressources biologiques de l’Hôpital Bichat; The French Society of Rheumatology.Disclosure of InterestsPierre-Marie DURET: None declared, Cédric Schleiss: None declared, Nathanaël Sedmak: None declared, Nicolas Meyer: None declared, Tao Ye: None declared, Lou Kawka: None declared, Alain Saraux: None declared, Valerie Devauchelle-Pensec: None declared, Divi Cornec: None declared, Claire Larroche: None declared, Aleth Perdriger: None declared, Raphaèle Seror: None declared, Renaud FELTEN: None declared, Jean Sibilia: None declared, Gaetane Nocturne: None declared, Xavier Mariette Consultant of: Astra Zeneca, BMS, Galapagos, GSK, Novartis, Pfizer, Jacques-Eric Gottenberg Consultant of: Astra Zeneca, BMS, Galapagos, GSK, Novartis, Pfizer.