Detection of K-ras mutations in DNAs isolated from feces of patients with colorectal tumors by mutant-allele-specific amplification (MASA).
K-ras mutations are found in approximately half of all colorectal tumors examined. To explore the possibility of detecting mutated K-ras rapidly and efficiently in DNAs isolated from fecal material, we applied the mutant allele specific amplification (MASA)-PCR method to DNA from feces of patients with colorectal tumors. Among 55 colorectal adenocarcinomas or adenomas examined, 19 were found to carry K-ras mutations in codons 12 or 13. We were able to PCR-amplify DNAs isolated from feces of 15 of these 19 patients, but in only three of the fecal samples, we were able to detect the K-ras mutations corresponding to tumor DNA by MASA and ethidiumbromide staining of the gel. The carcinomas in these three cases were more than 40 mm x 40 mm in size and located in the sigmoid colon or rectum. However, we identified the K-ras mutations in fecal DNAs of additional seven patients by MASA when the gels were blotted and probed with a radio-labeled oligonucleotide; the tumors in those patients had arisen in the distal half of the colon and the smallest of these tumors was only 7 mm x 5 mm. No K-ras mutations were detectable in feces of the remaining five cases, whose tumors were relatively small and/or located in the proximal region. The results suggested that the MASA-PCR system has potential for development as a simple, rapid and noninvasive method for diagnosing the presence of colorectal tumors that carry mutant K-ras alleles, particularly tumors located in the distal colon.
Hasegawa
Y
Y
Department of Biochemistry, Cancer Institute, Tokyo, Japan.
Takeda
S
S
Ichii
S
S
Koizumi
K
K
Maruyama
M
M
Fujii
A
A
Ohta
H
H
Nakajima
T
T
Okuda
M
M
Baba
S
S
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000235:genetics; D000236:Adenoma / Q000175:diagnosis* / Q000235:genetics; D000328:Adult; D000368:Aged; D000483:Alleles; D001483:Base Sequence; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000235:genetics; D017931:DNA Primers / Q000737:chemistry; D004273:DNA, Neoplasm / Q000235:genetics; D005243:Feces; D005260:Female; D011905:Genes, ras; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods
D017931:DNA Primers; D004273:DNA, Neoplasm