In a retrospective analysis of over 4000 PDAC tumor samples, mutant KRAS was seen in 81% of PDAC and was associated with higher M1 macrophages and cancer-associated fibroblast infiltration and lower CD4+/CD8+, natural killer (NK) cells, MSI-H status, and TMB compared to KRAS wild-type samples. This evidence concerns the gene KRAS and cancer.