Two forms of this protein have been identified in animal cells, one in cytosol and one in mitochondria. Activity of the cytosolic enzyme is high in proliferating cells and peaks during the S-phase of the cell cycle; it is very low in resting cells.
Elevations in serum TK-1 have been found to correlate with the return of breast and other forms of cancer[7] TK-1 can be used to detect cancer earlier, determine what stage it is in, and detect recurrence. Thymidine Kinase 1 can be measured based on its enzyme activity[8] or using immunoassay.[9]
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^He Q, Zhang P, Zou L, et al. (2005). "Concentration of thymidine kinase 1 in serum (S-TK1) is a more sensitive proliferation marker in human solid tumors than its activity". Oncol. Rep. 14 (4): 1013–19. PMID16142366.
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Kuo WL, Hirschhorn R, Huie ML, Hirschhorn K (1996). "Localization and ordering of acid alpha-glucosidase (GAA) and thymidine kinase (TK1) by fluorescence in situ hybridization". Hum. Genet. 97 (3): 404–6. doi:10.1007/BF02185782. PMID8786092. S2CID9056186.
Fujiwaki R, Hata K, Moriyama M, Iwanari O, Katabuchi H, Okamura H, Miyazaki K (2001). "Clinical value of thymidine kinase in patients with cervical carcinoma". Oncology. 61 (1): 47–54. doi:10.1159/000055352. PMID11474248. S2CID9006108.
Mao Y, Wu J, Wang N, He L, Wu C, He Q, Skog S (2002). "A comparative study: immunohistochemical detection of cytosolic thymidine kinase and proliferating cell nuclear antigen in breast cancer". Cancer Invest. 20 (7–8): 922–31. doi:10.1081/CNV-120005905. PMID12449723. S2CID23072666.
Gilles SI, Romain S, Casellas P, Ouafik L, Fina F, Combes T, Vuaroquaux V, Seitz JF, Bonnier P, Galiègue S, Carayon P, Martin PM (2003). "Mutation analysis in the coding sequence of thymidine kinase 1 in breast and colorectal cancer". Int. J. Biol. Markers. 18 (1): 1–6. doi:10.5301/jbm.2008.2452. PMID12699056.
Han T, Fernandez M, Sarkar M, Agarwal RP (2004). "2', 3'-Dideoxycytidine represses thymidine kinases 1 and 2 expression in T-lymphoid cells". Life Sci. 74 (7): 835–42. doi:10.1016/j.lfs.2003.07.023. PMID14659972.
Li CL, Lu CY, Ke PY, Chang ZF (2004). "Perturbation of ATP-induced tetramerization of human cytosolic thymidine kinase by substitution of serine-13 with aspartic acid at the mitotic phosphorylation site". Biochem. Biophys. Res. Commun. 313 (3): 587–93. doi:10.1016/j.bbrc.2003.11.147. PMID14697231.
Topolcan O, Holubec Jr L (2008). "The role of thymidine kinase in cancer diseases". Expert Opin. Med. Diagn. 2 (2): 129–41. doi:10.1517/17530059.2.2.129. PMID23485133.