Screening for novel serum biomarker for monitoring disease activity in rheumatoid arthritis using iTRAQ technology-based quantitative proteomic approach.

Useful biomarkers, which enable the prediction of drug susceptibility, identification of side effects, and/or evaluation of disease activity during drug treatment, are urgently needed to select adequate drugs for patients. Gene mutation status, protein expression levels in a biopsy, and serum proteins are often used as biomarkers. One of the methods to screen for protein biomarkers involves quantitative proteomic approaches using mass spectrometry. Owing to the development of quantitative proteomic approaches, the efficiency of identifying novel biomarkers from clinical samples has improved. In particular, isobaric tag for relative and absolute quantitation technology, which enables relative comparative analysis of up to eight samples, enables high-throughput analysis of screening for biomarkers at the protein level. Here, we describe the identification of a novel biomarker, which is useful for the evaluation of disease activity in patients with rheumatoid arthritis who were treated with anti-TNF-α therapy.