Previous studies have suggested that TGF-β can promote metastasis in lung cancer cells by combining with a relevant receptor in the cytomembrane and activating downstream proteins in EMT-related signaling pathways.123 An investigation explored a new mechanism by which TGF-β mediated metastasis and invasion in lung cancer cells, namely, TGF-β-treated A549 cells secreted exosomes with upregulated lnc-matrix metalloproteinase 2-2 (lnc-MMP2-2) expression, which promoted migration and invasion in other A549 cells, as well as permeability in vascular endothelial cells by increasing MMP2 expression. This evidence concerns the gene MMP2 and lung cancer.