CCN2 and silicosis: In this study, serum levels of S100A4, transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in patients with silicosis (n = 42) and control group (CG, n = 12) were measured by ELISA.