Background Myositis-specific antibodies in patients with inflammatory myopathies are known to be associated with various clinical manifestations, classifications and diagnosis. Among them, recently found anti-transcriptional intermediary factor 1 (TIF1) α, β, or γ antibodies, has been reported to be associated with dermatomyositis (DM) accompanied by cancer.
Objectives Although previous studies have evaluated the association of the antibodies in serum and clinical subtypes, the information about the target antigen is insufficient. The purpose of this study was to confirm the overexpression of TIF1s in the muscle and skin tissues of patients with inflammatory myopathies.
Methods From February 2004 to November 2014, skin and muscle biopsies were performed on 45 patients diagnosed with dermatomyositis and polymyositis. We stained skin and muscle tissue by immunohistochemistry using anti-TIF1α, β, or γ and compared with the results of healthy control. We analyzed the association between the clinical manifestations and protein expression in each tissue.
Results When compared with the control group, any antigens showed no significant overexpression in the muscle. However, TIF1α showed higher positive rate in the skin of DM (12/15 [80%]) than in the skin of healthy control (0/7 [0%]) (p=0.001). TIF1γ expression was higher in the muscle of patients with DM while there was no expression in the muscle of healthy controls (DM, 8/19 [80%] vs. healthy control 0/7 [0%], p=0.039).
In the tissues of inflammatory myopathies, TIF1α and TIF1γ demonstrated higher positive rates in the skin than in the muscle (TIF1α, muscle, 4/35 [11%] vs. skin, 12/15 [80%], p<0.001; TIF1γ, muscle, 10/35 [29%] vs. skin, 13/15 [87%], p<0.001). When analyzing DM patients only, the result was similar (TIF1α, muscle, 1/19 [5%] vs. skin, 12/15 [80%], p<0.001; TIF1γ, muscle, 8/19 [42%] vs. skin, 13/15 [87%], p=0.013). TIF1β showed strong positivity in all tissues of myositis or healthy control.
Analyzing the association with TIF1s expression and cancer, there was no significant difference in the positive rate of TIF1α or γ in the muscle or skin between the myositis patient with or without cancer.
Conclusions TIF1α was expressed more in the skin of DM patients than that in that of control group and TIF1γ in the muscle of DM patients than in that of control. The expression of TIF1α in the skin and TIF1γ in the muscle of cancer associated DM was not higher than those of DM without cancer. Thus the expression levels of TIF1α in the skin and TIF1γ in the muscle may be associated with myositis rather than with cancer.
Hoshino K, et al. Anti-MDA5 and anti-TIF1-gamma antibodies have clinical significance for patients with dermatomyositis. Rheumatology (Oxford) 2010;49(9):1726–1733.
Fiorentino D. Casciola-Rosen L, Autoantibodies to transcription intermediary factor 1 in dermatomyositis shed insight into the cancer-myositis connection. Arthritis Rheum 2012;64(2):346–349.
Disclosure of Interest None declared