Furthermore, PLK1 has few mutations (0.5%) compared with other genes (i.e., TP53, KRAS, CDKN2A, and SMAD4) that are frequently mutated in pancreatic adenocarcinoma in cBioPortal (https://www.cbioportal.org/)49,50, and the promoter methylation level did not differ from that in healthy pancreatic tissues. Here, SMAD4 is linked to pancreatic adenocarcinoma.