Lymphoma is the most common hematopoietic neoplasm (tumour affecting the blood-producing cells) in horses. Lymphomas are less common than sarcoids, squamous cell carcinoma and melanoma, and account for about 2% of all equine neoplasia.
Lymphomas can appear in different forms depending on which tissues are involved. Those involving the skin are easier to identify and treat. Tumours involving lymphoid tissue in the chest or abdominal organs are more of a challenge. They tend to produce non-specific signs such as fever, weight loss, colic, ventral oedema, and diarrhoea.
Confirmation of a diagnosis relies on identification of malignant lymphoid cells in blood or bone marrow, or in pleural or peritoneal fluid. An accurate serum biomarker would make the task much easier.
Thymidine kinase 1 (TK1) plays an important role in DNA replication and cell division. It is only present in cells when they are dividing and is quickly broken down afterwards. Cells dividing normally do not release significant amounts of TK1 into the extracellular body fluids, but cancer cells do.
Serum TK1 activity has been used as a biomarker for health screening for malignant diseases and to monitor response to treatment in humans and in dogs.
Liya Wang and colleagues at the Swedish University of Agricultural Sciences, Uppsala, Sweden and the University of Bern, and Agroscope, Bern, Switzerland, conducted a study to evaluate the serum level of TK1 as a biomarker for equine lymphoma.
They collected serum samples from healthy and diseased horses, and measured the levels of TK1.
They took blood from seven horses with confirmed lymphoma, five horses with suspected lymphoma, 107 control horses with concurrent diseases and 42 healthy horses.
They found that “serum TK1 activity was significantly higher in the lymphoma (p < 0.0005), suspected lymphoma (p < 0.02) and tumour-free with concurrent diseases (p < 0.03) groups than in the controls without concurrent diseases, and there was a significant difference between the lymphoma group and the tumour-free group with concurrent diseases (p < 0.0006).”
They conclude: “These results demonstrated that serum TK1 could serve as a useful biomarker to distinguish individuals with lymphoma from control horses with and without concurrent diseases.”
For more details, see:
Molecular characterization of equine thymidine kinase 1 and preliminary evaluation of its suitability as a serum biomarker for equine lymphoma.
Wang, L., Unger, L., Sharif, H. et al.
BMC Mol and Cell Biol (2021). 22, 59.