Objective—To measure telomere length and telomerase
activity in naturally occurring canine mammary
Sample Population—27 mammary gland tumor
specimens obtained during resection or necropsy and
12 mammary gland tissue specimens obtained from
healthy (control) dogs.
Procedure—Telomere length in tissue specimens
was measured by use of restriction endonuclease
digestion and Southern blot analysis. Telomerase
activity was measured by use of a telomeric repeat
amplification protocol assay.
Results—Telomere length in mammary gland tumors
ranged from 11.0 to 21.6 kilobase pairs (kbp; mean ±
SEM, 14.5 ± 0.5 kbp) but did not differ among tumor
types. Telomeres in mammary gland tumors were
slightly shorter than in normal tissue specimens, but
telomere length could not be directly compared
between groups, because mean age of dogs was significantly
different between groups. Age was negatively
correlated with telomere length in control dogs
but was not significantly correlated with length in
affected dogs. Telomerase activity was detected in 26
of 27 mammary gland tumors and in 4 of 12 normal
tissue specimens. However, telomerase activity and
telomere length were not correlated in tumor specimens.
Conclusion and Clinical Relevance—Telomere
length is maintained in canine mammary gland
tumors regardless of the age of the affected dog.
Measurement of telomere length may be a useful
tool for monitoring the in vivo effects of telomerase
inhibitors in dogs with tumors. (Am J Vet Res 2001;