Biological and biochemical effects of 2'-azido-2'-deoxyarabinofuranosylcytosine on human tumor cells in vitro.

2-azido-2'-deoxyarabinofuranosylcytosine (Cytarazid), recently synthesized, was found to inhibit the in vitro growth of several human cell lines by 50% at concentrations ranging from 0.06 to 0.2 microM and to prevent the replication of herpes simplex virus types 1 and 2 by 98% at 50 microM. As determined with HeLa cells, the inhibition of cell growth was partially prevented by 2'-deoxycytidine (dCyd) and cytidine but not by uridine or thymidine. Cytarazid proved resistant to deamination by human cytidine/dCyd deaminases purified from acute myelocytic leukemia blast cells and from liver, a property reflected in the inability of tetrahydrouridine to enhance the cytotoxicity of the compound. Cytarazid served as a substrate for cytoplasmic dCyd kinase partially purified from human peripheral chronic lymphocytic leukemia blast cells. At a concentration of 0.4 mM, the nucleoside analog was phosphorylated 2.6 times more effectively by this enzyme than was dCyd, the Km for Cytarazid being 250 microM. In intact HeLa cells, the triphosphate derivative of Cytarazid was the major drug metabolite formed. In these cells, the analog interfered with the incorporation of radiolabeled thymidine into DNA at a concentration and a time interval at which the incorporation of uridine into RNA and amino acids into protein was not inhibited, suggesting that interference with DNA synthesis is a primary drug effect. Further analysis showed that Cytarazid triphosphate interferes with DNA synthesis in intact HeLa cell nuclei and that it inhibits both the alpha- and beta-DNA polymerases purified from HeLa cells in a manner competitive with deoxycytidine triphosphate, with Ki's of 0.6 and 0.7 microM, respectively. Cytarazid triphosphate was not able to replace deoxycytidine triphosphate for the synthesis of DNA in either intact nuclei or in cell-free preparations; but, in the cell-free assay system, the compound was found to interfere with primer-template activity.

[1]  Y. Rustum,et al.  Biochemical effects of 2'-azido-2'-deoxyarabinofuranosyl cytosine (cytarazid) in leukemia l1210 and hela cells. Abstr. , 1980 .

[2]  Y. Cheng,et al.  Novel arabinofuranosyl derivatives of cytosine resistant to enzymatic deamination and possessing potent antitumor activity. , 1978, Journal of medicinal chemistry.

[3]  B. Chabner,et al.  Analysis of cytidine deaminase and tetrahydrouridine interaction by use of ligand techniques. , 1978, Biochemical pharmacology.

[4]  P. Fisher,et al.  DNA polymerase-alpha. Purification and structural characterization of the near homogeneous enzyme from human KB cells. , 1977, The Journal of biological chemistry.

[5]  Y. Cheng,et al.  Human deoxycytidine kinase. Purification and characterization of the cytoplasmic and mitochondrial isozymes derived from blast cells of acute myelocytic leukemia patients. , 1977, Biochimica et biophysica acta.

[6]  R. Sharma,et al.  Antiviral Action and Cellular Toxicity of Four Thymidine Analogues: 5-Ethyl-, 5-Vinyl-, 5-Propyl-, and 5-Allyl-2′-Deoxyuridine , 1976, Antimicrobial Agents and Chemotherapy.

[7]  David F. Wentworth,et al.  On the interaction of 3,4,5,6-tetrahydrouridine with human liver cytidine deaminase. , 1975, Biochemistry.

[8]  S. Greer,et al.  An assay for pyrimidine deoxyribonucleoside kinase using γ-32P-labeled ATP , 1975 .

[9]  W. Russell,et al.  A simple cytochemical technique for demonstration of DNA in cells infected with mycoplasmas and viruses , 1975, Nature.

[10]  Tetsuya Kato,et al.  Studies of Phosphorylation. III. Selective Phosphorylation of Unprotected Nucleosides , 1969 .