Neutrophil biomarkers predict response to therapy with tumor necrosis factor inhibitors in rheumatoid arthritis

Neutrophils are implicated in the pathology of rheumatoid arthritis (RA), but the mechanisms regulating their activation are largely unknown. RA is a heterogeneous disease, and whereas many patients show clinical improvement during TNF inhibitor (TNFi) therapy, a significant proportion fails to respond. In vitro activation of neutrophils with agents, including TNF, results in rapid and selective changes in gene expression, but how neutrophils contribute to TNF signaling in RA and whether TNFi sensitivity involves differential neutrophil responses are unknown. With the use of RNA sequencing (RNA-Seq), we analyzed blood neutrophils from 20 RA patients, pre-TNFi therapy, to identify biomarkers of response, measured by a decrease in disease activity score based on 28 joint count (DAS28), 12 wk post-therapy. Biomarkers were validated by quantitative PCR (qPCR) of blood neutrophils from 2 further independent cohorts of RA patients: 16 pre-TNFi and 16 predisease-modifying anti-rheumatic drugs (DMARDs). Twenty-three neutrophil transcripts predicted a 12-wk response to TNFi: 10 (IFN-regulated) genes predicting a European League against Rheumatism (EULAR) good response and 13 different genes [neutrophil granule protein (NGP) genes] predicting a nonresponse. Statistical analysis indicated a predictive sensitivity and specificity of each gene in the panel of >80%, with some 100% specific. A combination of 3 genes [cytidine monophosphate kinase 2 (CMPK2), IFN-induced protein with tetratricopeptide repeats 1B (IFIT1B), and RNASE3] had the greatest predictive power [area under the curve (AUC) 0.94]. No correlation was found for a response to DMARDs. We conclude that this panel of genes is selective for predicting a response to TNFi and is not a surrogate marker for disease improvement. We also show that in RA, there is great plasticity in neutrophil phenotype, with circulating cells expressing genes normally only expressed in more immature cells.