Background Biologics are an important subset of drugs used to treat rheumatoid arthritis (RA); however, up to 40% of patients have an inadequate response. Precision medicine aims to identify biomarkers that predict sub-populations of patients likely to respond to a given drug in order to optimise patient benefit. MicroRNAs (miRNAs) are small non-coding post-transcriptional regulators of gene expression. Dysregulation of several miRNAs have been implicated in RA and as such have been suggested as potential markers of disease activity. However, little research has been conducted into the potential clinical use of such biomarkers in predicting treatment response. We hypothesise that miRNA expression in pre-treatment serum samples of RA patients will provide such a biomarker.
Objectives To identify miRNA biomarkers in pre-treatment serum samples with sufficient power to differentiate between subsequent responder (R) and non-responder (NR) RA patients to the biologic drug, etanercept.
Methods Fifteen patients about to undergo treatment with etanercept were selected based on their EULAR response at 3-months from the Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate cohort. This equated to 6 extreme NR (disease activity score in 28-joints (DAS28) >5.1 and improvement <0.6 at follow-up) and 9 extreme R (DAS28 <2.6 and improvement >1.2 at follow-up); all were female and receiving concurrent methotrexate. MicroRNA was extracted from pre-treatment serum and expression of 754 miRNAs was measured on the TaqMan OpenArray Human miRNA Panel on the QuantStudio™ Real-Time qPCR System (Applied Biosystems). Raw data were processed using the Bioconductor package HTqPCR. Briefly, raw cycle threshold (CT) values were normalised to an endogenous spike-in control miR-ath159a using the deltaCt method and differential expression (DE) was conducted between R and NR.
Results Of the 754 miRNAs assayed, 405 were not expressed in any of the samples and were removed from further analysis; miRNAs were also excluded based on an amplification quality score (good amplification indicated by a score >1.1). This left 241 miRNAs for DE analysis. One circulating miRNA, miR-10b, was differentially expressed in pre-treatment samples (p-value =0.004), demonstrating higher relative expression in R vs. NR. A number of validated targets for miR-10b are pertinent to RA, including NOTCH1, a gene with a reported role in TNF induced proliferation of RA synoviocytes; SMRT, a negative regulator of interstitial MMP-1 synthesis and HOXD10, a transcription factor exclusively expressed in RA fibroblast-like synoviocytes (miRTarBase).
Conclusions Pilot data from this preliminary study suggests higher expression of miR-10b in pre-treatment RA serum is predictive of subsequent response to etanercept by 3 months. Although the findings require replication, the presence of a miRNA which is known to interact with RA related target genes adds support that circulating miRNAs could be useful predictive markers of response to etanercept in RA patients.
Acknowledgements SLS is a PhD student funded by an investigator-initiated award to AB from Pfizer (award WS1940162).
Disclosure of Interest None declared
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