Disease relevance of Dck

• Both mouse and human dCK were cloned into the T5 promotor pQE30 vector system, expressed in Escherichia coli and purified to homogeneity [1].
• Previous experiments have suggested that lymphospecific toxicity in this condition might result from the selective accumulation of toxic deoxyadenosine nucleotides by lymphocytes with high deoxycytidine kinase, levels and low deoxynucleotide dephosphorylating activity [2].
• Deoxycytidine kinase-mediated toxicity of deoxyadenosine analogs toward malignant human lymphoblasts in vitro and toward murine L1210 leukemia in vivo [2].
• However, protein isolated by affinity column chromatography from thymidine kinase-deficient mouse cells (LMTK-) infected by herpes simplex virus type 1 shows thymidylate kinase activity in addition to thymidine kinase and deoxycytidine kinase activities [3].
• Pool size studies of the fate of [14C]-CldC in BDF1 mice bearing Sarcoma-180 tumors, which demonstrated the rapid formation of 5-chlorodeoxycytidylate (CldCMP), and incorporation of CldC as such in RIF-1 tumor DNA, indicate that CldC is a substrate for deoxycytidine kinase, as our past Km studies have shown [4].

High impact information on Dck

• Mutant lymphoblasts, deficient in deoxycytidine kinase, with elevated cytoplasmic 5'-nucleotidase, or with expanded deoxynucleotide pools secondary to increased ribonucleotide reductase activity, were cross-resistant to both CAFdA and CdA toxicity [5].
• Each was phosphorylated in intact cells by deoxycytidine kinase accumulated as the nucleoside triphosphate, and inhibited DNA synthesis more than RNA synthesis [2].
• In most in vitro models, resistance to gemcitabine was associated with a decreased dCK activity [6].
• Gemcitabine is activated by dCyd kinase (dCK) and interferes, as its triphosphate dFdCTP, with tumor growth through incorporation into DNA [6].
• As with cytosine arabinoside, conversion to the monophosphate was catalyzed by cellular deoxycytidine kinase, which was essential for cytotoxicity [7].

Chemical compound and disease context of Dck

• The in vitro cytotoxic effects of DMDC and ara-C against L1210 leukemia cells were prevented dose dependently by deoxycytidine, suggesting that DMDC, like ara-C, may require phosphorylation by deoxycytidine kinase for antitumor activity [8].
• Metabolism and chemotherapeutic activity of 9-beta-D-arabinofuranosyl-2-fluoroadenine against murine leukemia L1210 and evidence for its phosphorylation by deoxycytidine kinase [9].
• The high Km for 5-chlorodeoxycytidine (56 microM) as compared with the low Km of deoxycytidine (2 microM) with respect to mammalian deoxycytidine kinase accounts, in great part, for the antagonism of toxicity [10].
• This hypothesis has been examined by measuring and comparing the incorporation of ara-C, OSI-7836, and gemcitabine (dFdC) into DNA of cultured cells and by investigating the role of deoxycytidine kinase in OSI-7836 toxicity [11].
• Differential affinities of pyrimidine nucleoside analogues for deoxythymidine and deoxycytidine kinase determine their incorporation into murine leukemia L1210 cells [12].

Biological context of Dck

• The kinetic constants for dCyd phosphorylation were similar for the human and mouse enzymes and also similar to what previously has been observed for dCK purified from human tissues [1].
• 2 cloning and expression of mouse deoxycytidine kinase. Pure recombinant mouse and human enzymes show differences in substrate specificity [1].
• We have cloned and sequenced the 20 kbp mouse dCK gene and approximately 1.7 kbp of the 5' flanking regions of both the human and mouse dCK genes [13].
• These results indicate that the dFdCyd resistance phenotype is stable, and mainly due to dCK deficiency [14].
• Reverse-transcribed and PCR-amplified mRNA, using specific dCK primers, demonstrated that AG6000 expressed a normal length amplicon of 701 base pairs, besides an aberrant amplicon of 500 base pairs [14].

Anatomical context of Dck

• The macrophages lacked both deoxycytidine kinase and deoxycytidine deaminase, which is consistent with their excretory pattern [15].
• In four cell lines (A2780, OVCAR-3, WiDr and UM-SCC-14C), sources for some of the above mentioned tumours, a different pattern in dCK and dCDA was observed than in the corresponding tumours [16].
• Leukemic and solid tumor cell lines that are resistant to cytosine arabinoside due to deletion of deoxycytidine kinase activity are cross-resistant to arabinosyl-5-azacytosine [17].
• With CdA as a substrate, the Michaelis constant (Km) of dCK in crude extracts of mouse thymus was 10 times higher than that in human thymus [18].
• To evaluate the potential of dCK to be used as suicide gene for deoxycytidine nucleoside analogs, we transduced both human A-549 lung carcinoma and murine NIH3T3 fibroblast cell lines with this gene [19].

Associations of Dck with chemical compounds

• Mouse dCK was less efficient with regard to dAdo, dGuo, and ddCyd phosphorylation as compared with human dCK when using ATP as phosphate donor in a phosphoryl transfer assay [1].
• These changes were not associated with alteration in the activity of deoxycytidine kinase, measured in extracts from L1210 cells both with and without deoxycytidine triphosphate [20].
• Deoxyadenosine kinase was clearly separated from deoxycytidine kinase [9].
• In Colon 26-G, dCK activity was 1.7-fold decreased; dCDA and DNA polymerase were not changed; and Colon 26-G accumulated 1.5-fold less dFdCTP, 6 hours after a gemcitabine injection, than the parental tumor [6].
• 2-F-ara-A and 9-beta-D-arabinofuranosyladenine 5'-formate were inactive aginst a 1-beta-D-arabinofuranosylcytosine-resistant subline (L1210/ara-C) that was deficient in deoxycytidine kinase [9].

Other interactions of Dck

• H4Urd treatment of 25 mg/kg did not affect the elevated levels of deoxycytidine kinase or deoxycytidylate deaminase in LLC tumor tissue or the low levels found in normal tissue [21].
• Cells lacking thymidine kinase or deoxycytidine kinase were just as sensitive as wild-type cells [22].
• A novel affinity chromatography method for the co-purification of deoxycytidine kinase and cytidine deaminase [23].

Analytical, diagnostic and therapeutic context of Dck

• Northern blot analyses revealed a size of 3.4 kb for mouse dCK mRNA as compared with 2.8 kb for human dCK [1].
• However, levels of dCK transcripts on Northern blots and protein levels on Western blots were nearly identical between CBS-transfected and wild-type cells [24].
• Whereas a modest tumor growth delay was observed in the wild-type tumors receiving dFdCyd, dCK xenografts demonstrated a marked tumor growth delay following treatment (P < or = 0.05) [25].
• RESULTS: HPLC experiments revealed an increased tumor accumulation of dFdCTP in xenografts overexpressing dCK compared with wild-type controls (P < or = 0.05). dFdCTP in the dCK-infected tumors was easily identified at 24 h postinjection [25].
• Deoxycytidine kinase (EC 2.7.1.74, dCK) catalyzes the phosphorylation of deoxynucleosides and several nucleoside analogues that are important in antiviral and cancer chemotherapy [26].

References