Multiple K-ras codon 12 mutations in cholangiocarcinomas demonstrated with a sensitive polymerase chain reaction technique.
By using a modified polymerase chain reaction strategy, we have devised an approach to detect a K-ras oncogene mutated at codon 12 in the presence of 1000 normal alleles. This is a considerable improvement in sensitivity on previous assays. Application of this assay to 15 cholangiocarcinomas showed that all contained a K-ras mutation to codon 12 and that nine of the tumors contained two or more mutations. In 11 cases, mutations were present in less than 10% of the cells in the sample. In common with pancreatic adenocarcinomas, in which 75 to 95% of cases contain a mutation in K-ras, cholangiocarcinomas show a very high frequency of ras gene mutation, but within a tumor only a fraction of cells contain a ras mutation. The presence of multiple mutations and the low frequency of mutant alleles in the samples argue against K-ras mutations being the initiating genetic lesion in this tumor, but suggest that ras gene mutation is involved in the stepwise progression of neoplastic cells to full malignancy.
Levi
S
S
Section of Cell and Molecular Biology, Chester Beatty Laboratories, Institute of Cancer Research, London, United Kingdom.
Urbano-Ispizua
A
A
Gill
R
R
Thomas
D M
DM
Gilbertson
J
J
Foster
C
C
Marshall
C J
CJ
D002759:Adenoma, Bile Duct / Q000235:genetics*; D011125:Adenomatous Polyposis Coli / Q000235:genetics; D001483:Base Sequence; D003062:Codon; D011905:Genes, ras; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009841:Oligonucleotides / Q000737:chemistry; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D014407:Tumor Cells, Cultured
D003062:Codon; D009841:Oligonucleotides; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)