Mutation Analysis of K-ras Codon 12 in Malignant Effusion

Huh, Jung Won; Chi, Hyun Sook

Abstract

BACKGROUND: Many studies suggest that point mutations of ras oncogene develop tumors. The advantages of body fluid analysis are easy accessibility and more simple procedure than tissue specimen. So, we investigated the incidence of K-ras codon 12 mutation in body fluids of patients with malignant solid tumors and tried to define the significance of K-ras codon 12 mutation in body fluids.
METHODS
We analyzed 58 specimens of body fluids in patients diagnosed as solid tumor. The first PCR products were digested with BstN1 and then followed the second PCR and BstN1 digestion. Nucleotide sequencing was performed by Sanger's method.
RESULTS
The incidences of K-ras codon 12 mutation are 75% in biliary cancer, 50% in pancreatic cancer, 31% in lung cancer, 14% in liver cancer, and 8% in stomach cancer. Mutations of K-ras codon 12 were detected in 24% (9/37) of body fluids with malignant cells and 19% (4/21) of body fluids without malignant cells. The proportions of malignant cells were not different between the patients with and without K-ras codon 12 mutation in effusions with malignant cells. Nucleotide sequencing on one sample of a patient with pancreatic carcinoma revealed single base substitution in codon 12 of K-ras gene from GGT to GAT.
CONCLUSIONS
The incidences of ras mutation in body fluids are variable with tumor type. Since K-ras codon 12 point mutation was highly specific, not in those of patients without tumors, examination of K-ras codon 12 point mutation may be an additive diagnostic tool for early detection of metastasis to body fluids.