KRAS and lung carcinoma: While mutations in KRAS are more frequent in pancreatic, colon and lung carcinomas, HRAS mutations are predominantly found in bladder cancer, and NRAS mutations are associated primarily with hematopoietic malignancies and melanomas.3 Each RAS protein is a 21 kDa guanine nucleotide binding protein with an intrinsic GTPase activity which transduces signals by interacting with the effectors only in the guanosine triphosphate (GTP)-bound conformation.