Meanwhile, PEAK1 overexpression promoted the transformation of polarized epithelial cells into fibroblast-like mesenchymal cells with a decrease in cell–cell adhesion and E-cadherin expression, and an increase in N-cadherin, MMP2, MMP9, and Zeb2 or Twist2 expression in different NSCLC cells, independent from the TGF-β level. The gene discussed is MMP9; the disease is non-small cell lung carcinoma.