Analysis of ras gene mutations in biliary and pancreatic tumors by polymerase chain reaction and direct sequencing.

Ras gene is one of the oncogenes most commonly detected in human cancers and consists of three families (H-ras, K-ras, N-ras) that are converted to active oncogenes by point mutations occurring in codon 12, 13, or 61. The authors analyzed mutations of these codons in 12 extrahepatic bile duct carcinomas, nine gallbladder carcinomas, and 20 pancreatic tumors (18 pancreatic adenocarcinomas and two islet cell tumors) by a method to directly sequence nucleotides, using polymerase chain reaction and a direct sequencing method. Point mutations at K-ras codon 12 were found in all of 18 pancreatic adenocarcinomas and in one bile duct carcinoma, but there were no mutations in the remaining 11 bile duct carcinomas, in all of 9 gallbladder carcinomas, or in two islet cell tumors. A very high incidence of ras gene mutations may be used clinically for the diagnosis of debatable cases of pancreatic adenocarcinoma.