PSME3 and rheumatoid arthritis: The PA28γ levels of cancer patients (median = 246 ng/ml; P = 0.003), RA patients (median = 27.8 ng/ml; P = 0.0002) and SS patients (median = 21.7 ng/ml; P = 0.008) were significantly higher compared with the healthy control group (median = 18.1 mg/ml).