CCNB1 and pancreatic ductal adenocarcinoma: Previous studies also showed that CDK1 was upregulated in several cancers and related with the prognosis, such as Piao et al. who found that CDK1 and BUB1 were upregulated and predicted poor prognosis of pancreatic ductal adenocarcinoma [27] and Zou et al. who also identified that CDK1, CCNB1, and CCNB2 were the prognostic biomarkers and correlated with immune infiltration in hepatocellular carcinoma [28].