Although recent studies reported that overexpression of PLK1 induces the EMT and promotes cell motility in prostate and gastric cancer [19, 20], it is not yet well understood whether the expression of PLK1 is required to induce metastasis in vivo and in NSCLC cancer patients or which is more important in inducing the EMT for metastasis in NSCLC, the expression of PLK1 or its activation. This evidence concerns the gene PLK1 and gastric cancer.