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  • Title: Substrate-specific deoxycytidine kinase deficiency in 1-beta-D-arabinofuranosylcytosine-resistant leukemic cells.
    Author: Richel DJ, Colly LP, Arkesteijn GJ, Arentsen-Honders MW, Kerster MG, ter Riet PM, Willemze R.
    Journal: Cancer Res; 1990 Oct 15; 50(20):6515-9. PubMed ID: 2208110.
    Abstract:
    In this study we describe the establishment of a leukemic cell line (BNML-CL/ara-C), originating from the 1-beta-D-arabinofuranosylcytosine (ara-C)-resistant brown Norway rat myelocytic leukemia model (BNML/ara-C), that retains the in vivo generated ara-C resistance. Its biological and biochemical characteristics have been compared with a cell line, derived from the ara-C-sensitive BNML model (BNML-CL/O). Resistance to ara-C was attributed to a decrease in phosphorylation of ara-C. Deoxycytidine (dCyd) kinase activity in crude cell extracts with dCyd as substrate showed similar enzyme activities in both cell lines, whereas with ara-C as substrate no dCyd kinase activity was detectable in the ara-C-resistant cell line. Two isoenzymes of dCyd kinase with different substrate specificities have been described (Cheng, Y.C., Domin, B., and Lee, L.S. Biochim. Biophys. Acta, 481: 481-492, 1977), cytoplasmic (dCyd kinase I, substrates: dCyd and ara-C) and mitochondrial (dCyd kinase II, substrates: dCyd and thymidine). In the ara-C-sensitive BNML model, thymidine induced a reduction of dCyd kinase activity when dCyd was used as substrate. However, thymidine did not affect kinase activity with ara-C was used as substrate. In the BNML-CL/ara-C, thymidine even induces a dCyd kinase inhibition of 85% with dCyd as substrate. It is likely that the ara-C-specific dCyd kinase deficiency in BNML-CL/ara-C cells was due to a selective loss of dCyd kinase I, whereas dCyd kinase II activity remained intact.
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