Analytical and clinical characterization of an optimized dual monoclonal sandwich ELISA for the quantification of thymidine kinase 1 (TK1) protein in human blood samples.

Thymidine Kinase 1 (TK1) plays an important role in DNA precursor synthesis and serum TK1 activity has been used as a biomarker for prognosis and therapy monitoring of different malignancies. AroCell has developed a dual monoclonal antibody ELISA for determination of TK1 protein in clinical samples. The purpose of the study is to validate the ELISA analytically in relation to the gold standard, [3H]-deoxythymidine (dThd) phosphorylation assay for TK1 activity using sera from patients with different malignancies. The colorimetric TK 210 ELISA was validated analytically by assessment of precision, linearity, interfering substances, and stability. For the clinical validation, serum samples from patients with hematological malignancies (n = 100), breast cancer (n = 56), prostate cancer (n = 70) and blood donors (n = 159) were analyzed using TK 210 ELISA and TK1 activity by [3H]-deoxythymidine (dThd) phosphorylation assay. The sandwich TK 210 ELISA was highly specific for TK1 protein having a detection limit of 0.12 ng/mL, with a functional sensitivity of 0.25 ng/mL. Within-run CVs ranged from 5.5% to 10% and between-run CVs ranged from 5% to 15%. The ratio of observed to expected dilutional parallelism of 5 serum samples was in the range of 80-120%. Samples exhibited stability through four freeze/thaw cycles and 5 days at 4°C. Further, the ROC curve analysis showed that TK 210 ELISA and [3H]-dThd phosphorylation assay had similar sensitivity (62% vs 59%) in hematological malignancies. However, in the case of breast and prostate cancer sera, TK 210 ELISA had higher sensitivity (59% and 44%) compared to [3H]-dThd phosphorylation assay (47% and 25%) at a specificity of 98%. These data demonstrate that the dual monoclonal antibody based AroCell TK 210 ELISA is a robust, accurate and precise tool for measuring TK1 protein in different malignancies that can improve the clinical applications of TK1 as a biomarker in cancer management.

Serum TK1 protein and C-reactive protein correlate to treatment response and predict survival in dogs with hematologic malignancies.

Thymidine kinase 1 (TK1), involved in DNA precursor synthesis, is used as a serum biomarker in cancer diagnostics in both human and veterinary medicine. We investigated the utility of serum TK1 protein (TK1p) and TK1 activity (TK1a) determinations for prognosis and monitoring of canine hematological malignancies. The combination of TK1p or TK1a with canine C-reactive protein (CRP) determinations was also investigated. Serum samples from 51 client-owned dogs with naive hematological malignancies and from 149 healthy subjects were included. Serum TK1p levels were determined using a prototype TK1-ELISA, TK1a using the [3H]-dThd phosphorylation assay, and CRP using an immunoturbidimetric assay. Mean TK1p in sera from dogs with tumors was significantly higher than from healthy dogs (mean ± SD = 3.9 ± 5.9 vs. 0.45 ± 0.15 ng/mL). Similarly, TK1a in hematological malignancies was significantly higher than in healthy dogs (mean ± SD = 15.1 ± 31.3 vs. 0.96 ± 0.33 pmol/min/mL). The receiver-operating characteristic indicated that a combination of TK1p or TK1a with CRP gave higher sensitivity than either biomarker alone for the prognosis of hematological malignancies. Median pretreatment TK1p and TK1a levels were significantly higher than in dogs in remission and correlated with clinical outcome. Kaplan-Meier curve analysis showed that naive dogs with high TK1p, TK1a, and CRP had significantly shorter survival. This study present two new polyclonal antibodies used in an ELISA system to determine TK1p. The study also show that combining TK1p or TK1a with CRP gave higher sensitivity than either biomarker alone. Monitoring patients in the study while undergoing chemotherapy, suggests that the TK1 + CRP combination could be useful in a biomarker panel, possibly aiding the prognosis and therapy monitoring of hematological malignancies in dogs.

Doxorubicin effects on leukemia and breast cancer cells in culture on the TK1 protein levels using AroCell TK 210 ELISA: a tool for drug development.

In this study changes in thymidine kinase 1 (TK1) levels after 24 hours of Doxorubicin (Dox) exposure of CEM and MDA MB-231 cells were determined using the commercially available AroCell TK 210 ELISA test. In cell extracts, TK1 levels increased twofold with 1 µM Dox in both cell lines, while the TK1 levels in the culture media increased with 5 and 10 µM of Dox only in case of CEM cells. In conclusion, this study reveals that the TK 210 ELISA can measure changes in intra- and extracellular TK1 levels apparently related to the mechanism of cytotoxicity of anti-cancer agents.