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.
Section of Cell and Molecular Biology, Chester Beatty Laboratories, Institute of Cancer Research, London, United Kingdom.
S
S
Levi
A
A
Urbano-Ispizua
R
R
Gill
D M
DM
Thomas
J
J
Gilbertson
C
C
Foster
C J
CJ
Marshall
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)