CD274 and pulmonary fibrosis: Consistent with pulmonary fibrosis, EMT signaling pathways involving TGF- β, such as Smad, PI3K/AKT, STAT3 and p53 pathways, also operate in hepatic fibrosis (110–113); secondly, PDL1 activates HSCs, resulting in the secretion of various substances, including ECM components, matrix metalloproteinases, tissue inhibitors of metalloproteinases, chemokines, growth factors, and TGF- β.