SHH and neoplasm: Although the mechanisms by which TGF-β1 can induce Hh ligand expression needs further investigation, our data clearly suggest that the activation of Shh signaling by TGF-β1 leads to increased tumor cell migration, invasion and tumorigenic potential of A549-M cells as documented by our mechanistic experiments using knock-down approach and by using chemical inhibitors of Shh signaling (Fig. 5A-C).