SNAI1 and lung carcinoma: Unexpectedly, H5N1 viruses did not increase but rather decreased the levels of Gli1 and Snail in a dose- and time-dependent manner in A549 (a human lung cancer cell line), NL20 (a human noncancerous alveolar epithelial cell line), and MDCK cells (a non-cancerous canine kidney cell line widely used for influenza virus study and for epithelial-to-mesenchymal transition) (Fig. 1a–c).