Immunoassays for detection of serum thymidine kinase 1 in dog lymphomas and carcinomas

Abstract: Serum thymidine kinase 1 (TK1) activity determination is used as marker for tumor monitoring in both human and veterinary medicine. TK1 is an intracellular enzyme involved in the salvage pathway of DNA precursor synthesis. TK1 expression is cell cycle dependent and the activity increases markedly at the end of G1 and reaches a peak value in S phase and then declines rapidly in G2 ∕M. The pronounced proliferation in tumor cells result in a higher TK1 activity within cell. So determination of TK1 activity in tumors provides information regarding prognosis and effectiveness of treatment. In human medicine, a labeled radioactive substrate is used for measuring TK1 activity. Some studies have shown that this method can be used also in veterinary medicine. However, it has limitation for general use in animal practice since it is expensive and involves handling of radioactive material. In human medicine, anti TK1 antibodies have been used to determine the concentration of serum TK1 in patients with carcinomas. This type of measurements has been successful and would be valuable to translate into veterinary medicine. The purpose of this study is to make the use of anti-dog TK1 antibodies for detection of serum TK1. Anti bodies have been produced by immunizing the rabbit with synthetic piece of a dog TK1 peptide. Suspected band of serum TK1 has been found in the serum from dogs with tumors but not in the serum from healthy dogs using these antibodies. This study showed that anti dog TK1 polyclonal antibodies produced by affinity chromatography binds to serum TK1 with adequate capacity. It has been also shown that these antibodies can bind with both human and dog cytosolic TK1. These results are the first step in the development of an ELISA, which may provide clinical information about prognosis, risk of recurrence and effectiveness of antitumor therapy in veterinary medicine.