title: A New Sandwich ELISA for Quantification of Thymidine Kinase 1 Protein Levels in Sera from Dogs with Different Malignancies Can Aid in Disease Management.
abstract: Thymidine kinase 1 (TK1) is a DNA precursor enzyme whose expression is closely correlated with cell proliferation and cell turnover. Sensitive serum TK1 activity assays have been used for monitoring and prognosis of hematological malignancies in both humans and dogs. Here we describe the development of a specific sandwich TK1-ELISA for the quantification of TK1 protein levels in sera from dogs with different malignancies. A combination of rabbit polyclonal anti-dog TK1 antibody and a mouse monoclonal anti-human TK1 antibody was used. Different concentrations of recombinant canine TK1 was used as standard. Clinical evaluation of the ELISA was done by using sera from 42 healthy dogs, 43 dogs with hematological tumors and 55 with solid tumors. An established [3H]-dThd phosphorylation assay was used to determine the TK1 activity levels in the same sera. The mean TK1 activities in dogs with hematological tumors were significantly higher than those found in healthy dogs. In agreement with earlier studies, no significant difference was observed in serum TK1 activities between healthy dogs and dogs with solid tumors. However, the mean TK1 protein levels determined by new TK1-ELISA were significantly higher not only in hematological tumors but also in solid tumors compared to healthy dogs (mean ± SD = 1.30 ± 1.16, 0.67 ± 0.55 and 0.27± 0.10 ng/mL, respectively). Moreover, TK1-ELISA had significantly higher ability to distinguish lymphoma cases from healthy based on receiver operating characteristic analyses (area under the curve, AUC, of 0.96) to that of the activity assay (AUC, 0.84). Furthermore, fluctuations in TK1 protein levels during the course of chemotherapy in dogs with lymphoma closely associated with clinical outcome. Overall, the TK1-ELISA showed significant linear correlation with the TK1 activity assay (rs = 0.6, p<0.0001). Thus, the new TK1-ELISA has sufficient sensitivity and specificity for routine clinical use in veterinary oncology.
authors.affiliation: Department of Anatomy, Physiology, and Biochemistry, Veterinary Medicine and Animal Science center, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Kiran Kumar
authors.initials: KK
authors.lastname: Jagarlamudi
authors.affiliation: Department of Anatomy, Physiology, and Biochemistry, Veterinary Medicine and Animal Science center, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Laura
authors.initials: L
authors.lastname: Moreau
authors.affiliation: University Animal Hospital, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Sara
authors.initials: S
authors.lastname: Westberg
authors.affiliation: Center of Clinical Comparative Oncology (C3O), Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Rönnberg
authors.affiliation: Department of Anatomy, Physiology, and Biochemistry, Veterinary Medicine and Animal Science center, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Staffan
authors.initials: S
authors.lastname: Eriksson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood; D004283:Dog Diseases / Q000097:blood*; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D019337:Hematologic Neoplasms / Q000097:blood / Q000662:veterinary; D008223:Lymphoma / Q000097:blood / Q000188:drug therapy / Q000662:veterinary; D008297:Male; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000097:blood / Q000662:veterinary*; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013937:Thymidine Kinase / Q000097:blood* / Q000276:immunology
chemical_list: D014408:Biomarkers, Tumor; D013937:Thymidine Kinase; C092717:thymidine kinase 1