Telomerase reverse transcriptase (TERT) expression in canine mammary tissues: a specific marker for malignancy?

Telomerase reverse transcriptase (TERT), the catalytic subunit of the enzyme telomerase, is expressed in virtually all human tumors. Telomerase activity has also been reported in the majority of canine tumors and dogTERT also correlates with the enzyme activity.

DogTERT expression in normal and malignant mammary tissues was investigated by immunohistochemistry and RT-PCR.

Using a highly specific TERT antibody in canins for the first time, immunoreactivity was identified in 46/50 malignant tumors, 26/50 adjacent to the tumor mammary tissues and 0/4 healthy mammary tissues. Two patterns of immunostaining were observed: cytoplasmic and concomitant nuclear and cytoplasmic. DogTERT mRNA was detected in 48/50 malignant tissues, 44/50 adjacent mammary tissues and in 2/4 healthy mammary tissues.

The observation that normal canine mammary epithelium expresses TERT challenges the conventional view that this gene is repressed in somatic and activated in malignant cells and supports the notion that dogTERT may not be a useful marker for canine mammary cancer.