Expression and localization of oncoproteins in rheumatoid synovial tissues

We examined the expression and localization of c-Fos and c-Myc oncoproteins in synovial tissues from 37 patients with rheumatoid arthritis (RA) by immunohistochemical staining, and compared them with the clinical findings, the laboratory data, the radiological assessment and the pathological features to determine whether or not any correlations exist. Immunohistochemical staining was performed by the avidin-biotin-peroxidase complex (ABC) method. After staining, we examined synovial lining cells, sublining cells (stromal cells and macrophage like cells) and focal aggregated lymphocytes under light microscopy. c-Fos was expressed in 12 patients (32%) and c-Myc was expressed in 28 patients (77%). On average, c-Fos was expressed in 11.9% of the synovial cells, and this rate was significantly higher than in both the sublining cells and focal aggregated lymphocytes. Similarly, c-Myc was expressed in 30.1% of synovial cells and this rate was significantly higher than in the focal aggregated lymphocytes. The expression of c-Myc in synovial and sublining cells was significantly correlated with the pathological features (the degree of synovitis). However, no correlation was observed between the expression and localization of c-Fos or c-Myc and the other data. Our results suggest that the oncoproteins c-Fos and c-Myc are significantly expressed in RA synovial cells, and that the level of expression reflects the degree of synovitis.