TGFB1 and pulmonary fibrosis: Additionally, Chiharu et al. reported all-trans retinoic acid (ATRA) inhibits both proliferation and transdifferentiation of lung fibroblasts through downregulating TGF-β expression and suppressing the IL-6/IL-6R system (IL-6 stimulates lung fibroblast proliferation in a dose-dependent manner), thereby preventing radiation- and bleomycin-induced pulmonary fibrosis in mice (37).