HMGA2 and pulmonary fibrosis: For example in the process of pulmonary fibrosis, transforming growth factor β1 (TGF-β1) can bind to the let-7d promoter through Smad3, resulting in down-regulation of let-7d, which further up-regulates the high mobility group protein A2 (HMGA2) of its target gene, promotes EMT, and leads to fibrosis (Pandit et al., 2010).