PLK1 and cancer: We further applied the TIMER2 approach to analyze the expression of CDK1, CCNB1, and PLK1 across various cancer types in The Cancer Genome Atlas (TCGA) and found that CDK1, CCNB1, and PLK1 were remarkably upregulated in multiple tumor tissues as compared with the adjacent normal tissues (Figures S1A–C), indicating that the activity of CDK1/CCNB1/PLK1 signaling was frequent even in human malignant tumors.