SMAD4 and pancreatic adenocarcinoma: Combined with 6 well-recognized biomarkers (i.e., KRAS, TP53, SMAD4, BRCA1, BRCA2, and CDKN2A) in pancreatic adenocarcinoma (PAAD), they were subjected to mainstream machine learning procedures to develop a Cuproptosis-related gene index (CRGI) (59).