A4.4 Circulating Metastasis Promoting Protein S100A4 in Idiopathic Inflammatory Myopathies

Abstract

Background and Objectives Metastasis promoting protein S100A4 is involved in the pathogenesis of tumours and chronic autoimmune diseases such as rheumatoid arthritis (RA) and psoriasis. We recently described increased expression of S100A4 in inflamed muscle tissue in patients with idiopathic inflammatory myopathies (IIM). Since circulating levels of S100A4 correlate with disease severity in RA patients, we therefore evaluated the association between S100A4 protein and disease activity in patients with IIM and compared S100A4 serum levels in myositis patients and healthy controls in this study. Methods Serum levels of S100A4 protein were determined in 43 dermatomyositis (DM), 39 polymyositis (PM) and 22 cancer associated myositis (CAM) patients and in 89 healthy controls. In 11 patients (4 DM, 3 PM, 4 CAM), S100A4 serum levels were measured before and after the start of treatment. The associations between S100A4 levels, inflammation, disease activity and muscle strength were examined. Disease activity was assessed using Disease Activity Core Set Measures developed by International Myositis Assessment & Clinical Studies Group (IMACS). Serum levels of C-reactive protein (CRP) and muscle-associated enzymes creatine phosphokinase (CK) and lactate dehydrogenase (LD) were measured by routine laboratory methods. Results In patients with PM, serum levels of S100A4 protein were significantly higher than those observed in healthy controls or DM patients (148.6 ± 351.5 versus 80.75 ± 285.1, p Conclusions This is the first study showing that circulating levels of S100A4 are associated with several features of IIM disease activity, particularly with extramuscular components. We did not find any association of S100A4 levels and cancer associated myositis. Further studies analysing bioactive form of S100A4 and the role of S100A4 in cancer associated myositis are needed.