“Based on our findings to date, we believe this tool may prove to be useful to help us rapidly diagnose malignancies,” said oncologist Barbara E. Kitchell, a professor of veterinary clinical medicine at the University of Illinois College of Veterinary Medicine. “And the enzyme involved in this method may well serve as a therapeutic target in feline and canine tumors.”
UI researchers, in two studies, used a simple protein test known as TRAP (Telomeric Repeat Amplification Protocol) to detect telomerase activity in cells taken from tissues and fluids of dogs and cats that were brought in for examination at the UI small animal hospital.
Telomerase is an enzyme that, in cancer, becomes active and interferes with the body’s ability to destroy aging cells. Instead of dying, cancerous cells continue to replicate. The enzyme is rarely found in normal cells.
Original data documenting TRAP’s use in human cancer detection were published in 1994, with 90 of 101 human malignant tumors and none of 50 benign human tissues showing telomerase activity. A later review of all pre-1996 studies concluded that most malignant tumors were telomerase positive.
UI veterinarians since 1997 have been using TRAP on both dogs and cats to successfully differentiate between malignant and inflammatory conditions, Kitchell said.
Their most recently published study, on cats, in the American Journal of Veterinary Research (October), documented that telomerase activity was present in 29 of 31 malignant and just one of 22 benign samples examined over two years. Not finding its activity in the two malignant tumors likely was the result of errors in tissue processing, Kitchell said.
“The malignant samples included vaccine-induced sarcomas, osteosarcomas and lymphosarcomas,” Kitchell said. “Telomerase activity appears to be a unique feature of benign tumor cells that have undergone malignant transformation.”
In a previous study of dogs, published in the same journal in 1998, Kitchell and colleagues reported that, in a study of tissue samples, 24 of 26 malignant tumors, one of four benign tumors and none of three normal tissues tested positive for telomerase activity. Of 46 fluid samples, 12 of 16 malignant and just one of 30 normal benign fluids showed signs of the enzyme’s activity.
“Though we tested a small number of samples,” the authors wrote in the cat study, “we feel that the correlation of our results with histopathology is sufficient to warrant further research on the application of this assay as a diagnostic tool at institutions with the correct storage facilities.” Authors of the recent cat study were Kitchell, Casey D. Cadile, Barbara J. Biller, Elizabeth R. Hetler and Rebecca Balkin. The Morris Animal Foundation provided partial funding for the research.
Journal
American Journal of Veterinary Research