Low Expression of the Deoxycytidine Kinase (dCK) Gene in a 1-β-D- Arabinofuranosylcytosine-Resistant Human Leukemic Cell Line KY-Ra

Molecular change of the deoxycytidine kinase (dCK) gene in a 1-beta-D-arabinofuranosylcytosine-resistant human leukemic cell line (KY-Ra) was investigated. KY-Ra showed the same restriction pattern of genomic DNA and the same nucleotide sequences of the dCK gene as the parental cell line. However, the amount of deoxycytidine kinase mRNA was markedly decreased in KY-Ra compared to the parental cell line. This is the first report showing that the down regulation of dCK gene expression may be affected by a different mechanism than mutation.