Detection of point mutations in K-rasgene at codon 12 in bile from percutaneous transhepatic choledochal drainage tubes for diagnosis of biliary strictures

摘要

Detection of K-rasmutations at codon 12 constitutes one modality for diagnosis of pancreatic tumors. We attempted to detect K-rasmutations in DNA from bile collected through percutaneous transhepatic choledochal drainage (PTCD) tubes as a diagnostic approach to biliary strictures. Since bile salts induce cell damage, we first investigated the degeneration of cells according to bile exposure time using cell lines. High-mol-wt DNA could be extracted from cells exposed to bile for 6 h, but not from those exposed for 12 h. However, DNA exposed to bile for up 12 h could be amplified by the polymerase chain reaction (PCR) method. Therefore, K-rasmutations in fresh bile specimens collected from 15 patients through PTCD tubes were examined using PCR with restriction enzyme digestion. K-rasmutations were found in five out of five (100) pancreatic cancers, all of which were negative according to cytodiagnosis of the same bile. On the other hand, K-rasmutations were not detected in bile from biliary tract cancers or metastatic neoplasms, except for one bile duct carcinoma and one metastatic case. Thus, although K-rasmutation alone is not an absolute marker for cancer, detection of K-rasmutations in fresh bile from PTCD tubes is a useful adjunct for diagnosis of pancreatic carcinomas in cases of biliary tract strictures.