Clinical phenotype with high risk for initiation of biologic therapy in rheumatoid arthritis: a data-driven cluster analysis.

OBJECTIVES: The clinical manifestations and treatment outcome in patients with rheumatoid arthritis (RA) are heterogeneous. We classified RA patients into subgroups with distinct phenotypes through unsupervised clustering and evaluated the utility of this subclassification for evaluation of clinical outcome. METHODS: A total of 1,103 patients with RA were clustered in an unbiased manner using a k-means clustering method, based on their clinical and phenotypic profiles. Initiation of biological disease-modifying anti-rheumatic drugs (bDMARDs) was evaluated in the segregated clusters to investigate the differential clinical course of each cluster. RESULTS: Patients with RA were classified into four clusters, each with distinct phenotypes. The key features for subclassification were sex, smoking, hypertension, and dyslipidaemia. Cluster 1 consisted of male smokers, who were most likely to initiate bDMARDs by 30 months (p=0.04). Multivariate analysis revealed that overweight, smoking, erythrocyte sedimentation rate, autoantibodies of high titre, and disease activity were the independent predictors of bDMARD initiation at 30 months. Cluster 1 was the highest or the second highest for these independent predictors, suggesting that cluster 1 contained a high-risk group for early initiation of bDMARDs. CONCLUSIONS: The unsupervised clustering of RA patients demonstrated the feasibility of the novel subclassification with respect to predicting clinical outcome. Identifying high-risk patients by a combination of clinical parameters may be useful for the management of RA.

Leukocyte-specific protein 1 regulates T-cell migration in rheumatoid arthritis.

Copy number variations (CNVs) have been implicated in human diseases. However, it remains unclear how they affect immune dysfunction and autoimmune diseases, including rheumatoid arthritis (RA). Here, we identified a novel leukocyte-specific protein 1 (LSP1) deletion variant for RA susceptibility located in 11p15.5. We replicated that the copy number of LSP1 gene is significantly lower in patients with RA, which correlates positively with LSP1 protein expression levels. Differentially expressed genes in Lsp1-deficient primary T cells represent cell motility and immune and cytokine responses. Functional assays demonstrated that LSP1, induced by T-cell receptor activation, negatively regulates T-cell migration by reducing ERK activation in vitro. In mice with T-cell-dependent chronic inflammation, loss of Lsp1 promotes migration of T cells into the target tissues as well as draining lymph nodes, exacerbating disease severity. Moreover, patients with RA show diminished expression of LSP1 in peripheral T cells with increased migratory capacity, suggesting that the defect in LSP1 signaling lowers the threshold for T-cell activation. To our knowledge, our work is the first to demonstrate how CNVs result in immune dysfunction and a disease phenotype. Particularly, our data highlight the importance of LSP1 CNVs and LSP1 insufficiency in the pathogenesis of RA and provide previously unidentified insights into the mechanisms underlying T-cell migration toward the inflamed synovium in RA.