Our heat map analysis revealed that the expression of PLK1 messenger RNA (mRNA) was increased in TGF-β-treated NSCLC cells such as A549 cells, when the mesenchymal markers, N-cadherin (CDH2), snail (SNAI1), and slug (SNAI2), were high and the epithelial marker E-cadherin (CDH1) or occludin (OCLN) was low. The gene discussed is SNAI1; the disease is non-small cell lung carcinoma.