LEF1 and idiopathic pulmonary fibrosis: While the mechanisms underlying EMT in IPF are still unclear, many EMT-related genes such as transforming growth factor (TGF)-β3 [26,27], lymphoid enhancer factor-1 (LEF-1) [28], and Slug, a TGF-β target gene required for EMT, as in the developing chicken heart [27], are up-regulated in IPF lungs (Table 1).