SMO and lung cancer: In lung squamous cell carcinoma (LSCC), HH signaling regulates EMT-associated proteins, such as E-Cadherin and β-catenin to induce the EMT process (17), and Smo gene amplification is one of the mechanisms through which HH signaling is activated to increase the resistance of lung cancer cells to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) by inducing the EMT process (18).