Serum Thymidine Kinase Activity in Dogs with Malignant Lymphoma: A Potent Marker for Prognosis and Monitoring the Disease

Abstract

Serum thymidine kinase (sTK) activity was evaluated as a tumor marker for canine malignant lymphoma (ML). The objective was to investigate if sTK, as in humans, could be used as a prognostic marker for survival time in dogs with ML and if sTK could identify early signs of progression of disease in treated dogs. Serum samples from 52 dogs with ML were tested for initial TK activity. Samples from 21 normal dogs and 25 dogs with nonhematologic neoplasms were used for comparison. Forty-four dogs with ML were treated. Serum TK activity was measured in treated dogs before each treatment and every 4 weeks thereafter until relapse. Dogs with ML had 2-180 times higher TK activity (TK 5-900 U/L) than normal dogs (TK Ͻ7 U/L) based on the mean ϩ 2 standard deviations. In the group of other neoplasms, only 2 dogs had a moderate increase (6.4 and 7.5 U/L) compared with the controls. Mean sTK activities in the dogs with ML that had gone into complete remission (CR) were not significantly different from activities in healthy controls (P ϭ .68). Mean sTK at least 3 weeks before and at the time of relapse was significantly higher than activity measured at CR (P Ͻ .0001). Dogs with ML that initially had sTK Ͼ30 U/L had significantly shorter survival times (P Ͻ .0001). Furthermore, sTK activity reflected the clinical staging of ML. Measuring sTK can be used as a powerful objective tumor marker for prognosis and for predicting relapse before recurrence of clinically detectable disease in dogs with ML undergoing chemotherapy.

Quaternary structures of recombinant, cellular, and serum forms of Thymidine Kinase 1 from dogs and humans

“…Recently serum TK1 activity has been used as biomarker for the diagnosis and prognosis of canine malignant lymphoma and leukemia [11,15,22,23]. However, the canine TK1 enzyme has not been characterized.…”

Thymidine Kinase Type 1 and C‐Reactive Protein Concentrations in Dogs with Spontaneously Occurring Cancer

“…[4][5][6][7][8][9][10] Increased plasma and serum TK1 activity occurs in dogs with lymphoma and higher activity correlates with advanced stage of disease as well as poorer prognosis. [11][12][13][14][15][16] TK1 has also been investigated in dogs with hemoabdomen and correlates with the presence of hemangiosarcoma. 17 TK1, in conjunction with measurement of serum canine-specific C-reactive protein (cCRP), has been useful when screening clinically healthy dogs for occult cancer.…”

Serum thymidine kinase activity in clinically healthy and diseased cats: a potential biomarker for lymphoma

“…However, it has been shown that sTK stability is maintained despite different durations and temperatures of storage, so this was not thought to have influenced the results. 11 Small-scale studies have been performed by one of the authors (H. von Euler, unpublished observations), demonstrating feline sTK stability despite storage and repeated freezing, and thawing.…”

“…Cases that met the following inclusion criteria were included in the study: age greater than 6 months (owing to potential effects of age on TK activity levels), 11 availability of non-haemolysed stored excess serum, complete case history and follow-up information according to specific group requirements as detailed below.…”