Furthermore, we verified the status of PLK1 between lung squamous cell carcinoma and lung adenocarcinoma through qRT-PCR, and found that the levels of PLK1 mRNA was overexpressed in lung squamous cell carcinoma tissues compared with lung adenocarcinoma tissues with an average increase of 2.65-fold (P<0.001, Figure 1C). This evidence concerns the gene PLK1 and squamous cell lung carcinoma.