The clinical significance of thymidine kinase 1 measurement in serum of breast cancer patients using anti-TK1 antibody

The activity of total thymidine kinase in serum (S-TK) has been used as a t umor maker for decades. To date such activity has been determined using I-( 125)-iodo-deoxyuridine as a substrate. The aim of this study was to develop a new, antibody-based technique for the measurement of cytoplasmic thymidi ne kinase (TK1) in serum. Both mono- and polyclonal antibodies against S-TK 1 were used in dot blot assay. S-TK1 was characterized by SDS and IEF techn iques. Sixty-five breast cancer patients were studied, including 17 preoper ative and 38 postoperative tumor-free patients and 10 patients with metasta ses to the lymph nodes (N1-2). They were compared to patients with benign t umors (n = 21) and healthy volunteers (n = 11). S-TK1 was low (0-1.0 pM) in healthy volunteers, while in preoperative patients the level was increased 6-110-fold. Significant differences were observed between preoperative pat ients and healthy volunteers (p = 0.005), preoperative patients and patient s with benign tumors (p < 0.001), and preoperative patients and postoperati ve patients without metastases (p < 0.001). No significant difference was o bserved between preoperative patients and postoperative patients with metas tases (p = 0.191). The S-TK activity in preoperative patients was also high in serum, but no decrease was observed following surgery. In conclusion, t he anti-TK1 antibody could be a good marker for monitoring the response of breast cancer patients to therapy.