To evaluate the role of endogenous EFR3A in a cancer driven by an oncogenic mutation in the native KRAS gene, we targeted EFR3A, EFR3B, or both genes by CRISPR/Cas9-mediated gene inactivation as above in the KRAS-mutant human pancreatic adenocarcinoma cell line HPAF-II47. The gene discussed is EFR3B; the disease is cancer.