CXCL16 and pulmonary fibrosis: Second, we did not investigate the possible relationship between CXCL16 and other signal transduction pathways in EMT such as Wnt, Notch, Hedgehog, etc. Additional studies (e.g. in primary epithelial cells, animal models, human tissues) are necessary to elucidate the functional role of CXCL16 in modulating EMT in pulmonary fibrosis.