Microsatellite instability in canine mammary gland tumors.
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).


OBJECTIVE
We hypothesized that MSI can be observed in canine mammary gland tumors (MGT) and represents a potential carcinogenic mechanism in dogs.


METHODS
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
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.
McNiel
Elizabeth A
EA
Departments of Veterinary Clinical Sciences, University of Minnesota College of Veterinary Medicine, Saint Paul, Minnesota 48824, USA. mcniel@cvm.msu.edu
Griffin
Kelly L
KL
Mellett
Amelia M
AM
Madrill
Nicole J
NJ
Mickelson
James R
JR
D000818:Animals; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D004283:Dog Diseases / Q000235:genetics*; D004285:Dogs; D019075:Electrophoresis, Capillary / Q000662:veterinary; D005260:Female; D005838:Genotype; D015674:Mammary Neoplasms, Animal / Q000235:genetics*; D053842:Microsatellite Instability; D018895:Microsatellite Repeats; D016133:Polymerase Chain Reaction / Q000662:veterinary
D004273:DNA, Neoplasm