Notably, increased SPP1 mRNA has been reported in tumor necrosis factor (TNF)-induced lung fibrosis in mice (Miyazaki et al. 1995), which may be of particular importance in the pathogenesis of silica-induced lung disease because lung TNF is increased in silicosis patients (Vanhée et al. 1995) and in silica-treated mice (Ortiz et al. 1998). Here, SPP1 is linked to pulmonary fibrosis.