PTK2 and pulmonary fibrosis: FAK-1 is a non-receptor tyrosine kinase [40] involved in lung fibrosis through the FAK/ERK/S100A4 signaling pathway [84], resulting in the cytoskeletal remodeling and fibroblast migration, proliferation, and differentiation into myofibroblasts; the emerging myofibroblasts start secreting high levels of collagen and α-smooth muscle actin (α-SMA) [15,31], substances which, in return, amplify the over-expression of FAK-1 [84].