Using isogenic cell lines, we showed here that compared with the parental human pancreatic duct epithelial E6E7 cells, K-ras–transformed pancreatic cancer cells exhibited a substantial increase in basal ROS levels, including both O2− and H2O2, indicating that the primary elevated generation of O2− may lead to an increase in H2O2 due to intracellular conversion. Here, KRAS is linked to pancreatic neoplasm.