PLK1 and esophageal squamous cell carcinoma: Interestingly, our microarray profile expression analysis also revealed that six genes, well known to be regulated by FOXM1, were also overexpressed in ESCC: PLK1 (2.9-fold), CDK1 (3.3-fold), CCNB1 (2.4-fold), ETV5 (3.3-fold) MMP9 (5.2-fold), and MMP12 (28.2-fold).