SMAD4 and pancreatic adenocarcinoma: The analysis of driver genes showed that in the TCGA-PAAD cohort, patients with DDR-subtype1 showed higher mutation frequencies of KRAS (90.7%) and SMAD4 (30.8%) than patients with DDR-subtype2 (Figure 3C); patients with DDR-subtype2 were dominated by TP53 (83.8%) and CDKN2A (24.3%) mutations (Figure 3D).