Microsatellite instability in canine mammary gland tumors

Elizabeth A. McNiel, Kelly L. Griffin, Amelia M. Mellett, Nicole J. Madrill, James R. Mickelson

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Background: Genomic instability is a hallmark of cancer and may be required for the accumulation of cancer-causing mutations within cells. One form of genomic instability occurs in tandem nucleotide repeats and is known as microsatellite instability (MSI). Hypothesis: We hypothesized that MSI can be observed in canine mammary gland tumors (MGT) and represents a potential carcinogenic mechanism in dogs. Animals: Thirty-five dogs with MGTs and 9 dogs with other tumors were recruited from the University of Minnesota Veterinary Medical Center and referring veterinary clinics. Methods: A panel of 21 canine microsatellite (MS) markers was amplified by polymerase chain reaction (PCR) from deoxyribonucleic acid obtained from blood and from fresh or formalin-fixed, paraffin-embedded tumor tissues. PCR products were evaluated by using capillary electrophoresis, and the chromatograms were analyzed by using genotyping software. MS genotypes obtained from fresh and formalin-fixed tumor tissues were compared, as were MS genotypes from normal tissue and tumor tissue. Results: Genotypes obtained from formalin-fixed and fresh tissues were identical for all MS in 9 tumors evaluated, suggesting excellent concordance between the 2 sample types. For the 35 canine mammary tumors evaluated, 13 (37%) had stable genotypes; 22 (63%) exhibited aberrations in 1 or 2 MS; and 4 tumors (11%) demonstrated high-level instability, with aberrations in 29 to 61% of MS. Conclusions and Clinical Importance: Although some low-level MSI often is observed, high-level MSI is an infrequent finding in canine mammary tumors. Further evaluations are required to better characterize this phenomenon and to determine its relevance to canine carcinogenesis.

Original languageEnglish (US)
Pages (from-to)1034-1040
Number of pages7
JournalJournal of veterinary internal medicine
Issue number5
StatePublished - Sep 2007


  • Carcinogenesis
  • Genomic instability
  • Mismatch repair
  • Mutation


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