Elevated levels of thymidine kinase 1 peptide in serum from patients with breast cancer

OBJECTIVES: Thymidine kinase (TK) has an important role in DNA synthesis and is thus related to cell proliferation and turn-over. Traditionally, TK has been measured by enzymatic activity or radioimmunoassays. These assays are difficult to adapt to random access instruments. The aim of this study was to evaluate a new immunological sandwich assay for detection of TK peptides in serum from breast cancer patients. MATERIAL AND METHODS: Serum samples were collected from patients with breast cancer and stored frozen at −70°C. The samples were collected after surgery, after metastatic tumor recurrence and after chemotherapy due to tumour recurrence. Patients’ serum samples were analysed by the TK enzyme-linked immunosorbent assay (ELISA). RESULTS: In receiver operating characteristics (ROC) analyses of TK1 for diagnosis of breast cancer, the area under the curve (AUC) collected four weeks after surgery was 0.56 (95% CI 0.47–0.65), for samples collected postsurgically after tumour recurrence 0.73 (95% CI 0.65–0.80), and after chemotherapy 0.64 (95% CI 0.56–0.72). CONCLUSIONS: This study indicates that the tumour proliferation marker TK has a potential as a serum marker in breast cancer. Further studies are warranted to verify this observation.