Point mutation of K-ras gene codon 12 in biliary tract tumors

Point mutations of the K-ras gene have been reported in a wide variety of human tumors. However, there might be conflicting data about its presence or incidence in biliary tract tumors. The aim of this study is to elucidate the presence and types of point mutation in biliary tract tumors, including gallbladder carcinoma and adenoma, extrahepatic bile duct carcinoma, and ampullary carcinoma.

Mutation bands detected in modified two-step polymerase chain reaction were eluted from agarose gel and analyzed by dideoxy sequencing method.

Of 20 biliary tract tumors showing a mutation band, G to A single base substitutions were confirmed in 15 cases as the most frequent changes, which were divided into changes for aspartic acid (GAT) and (14) serine (AGT) (1). Changes for valine (GTT) were found in two cases. In extrahepatic bile duct carcinoma, duplicate mutations (GA/TT) were found in two cases and triplicate mutation (A/GA/TT) in one case. The adenoma portion of one "cancer in adenoma" case of gallbladder showed the single base transition (GAT) in the second position, same as in the carcinoma portion.

Most of the biliary tract tumors comprised point mutation in K-ras gene codon 12, and G to A transition was the most frequent.