SMAD4 and pancreatic adenocarcinoma: As PAAD occupied a large proportion of cluster 1, we compared the genomic differences between the cluster 1 subgroup and the non-cluster 1 subgroup, we found that the C1 subgroup of PAAD was accompanied by a higher mutation rate of KRAS and SMAD4, suggesting a potential mechanism for the poor prognosis of cluster 1 patients (Figures 3E, F).