Detection of K-ras mutations in DNAs isolated from feces of patients with colorectal tumors by mutant-allele-specific amplification (MASA)

Oncogene. 1995 Apr 6;10(7):1441-5.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / diagnosis*
  • Adenocarcinoma / genetics
  • Adenoma / diagnosis*
  • Adenoma / genetics
  • Adult
  • Aged
  • Alleles
  • Base Sequence
  • Colorectal Neoplasms / diagnosis*
  • Colorectal Neoplasms / genetics
  • DNA Primers / chemistry
  • DNA, Neoplasm / genetics
  • Feces
  • Female
  • Genes, ras*
  • Humans
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Point Mutation
  • Polymerase Chain Reaction / methods


  • DNA Primers
  • DNA, Neoplasm