2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine: a novel anticancer nucleoside analog that causes both DNA strand breaks and G(2) arrest.
The mechanism of 2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine (CNDAC) action was investigated in human lymphoblastoid CEM cells and myeloblastic leukemia ML-1 cells. CNDAC was metabolized to its 5'-triphosphate and incorporated into DNA, which was associated with inhibition of DNA synthesis. After incubation of cells with [(3)H]CNDAC, metabolites were detected in 3'-->5' phosphodiester linkage and at the 3' terminus of cellular DNA. Specific enzymatic hydrolysis of DNA demonstrated that the parent nucleoside and its 2'-epimer 2'-C-cyano-2'-deoxy-2-ribo-pentofuranosylcytosine accounted for approximately 65% of the total analogs incorporated into DNA and essentially all of the drug in the 3'-->5' phosphodiester linkage. In contrast, all detectable radioactivity at 3' termini was associated with 2'-C-cyano-2',3'-didehydro-2',3'-dideoxycytidine. This de facto DNA chain-terminating nucleotide arises from an electronic characteristic and cleavage of the 3'-phosphodiester bond subsequent to the addition of a nucleotide to the incorporated CNDAC moiety by beta-elimination, a process that generates a single strand break in DNA. Investigation of the biological consequences of these actions indicated that, after incubation with cytostatic concentrations of CNDAC, cell cycle progression was delayed during S phase, but that cells arrested predominantly in the G(2) phase. This differed from the S phase-arresting actions of ara-C and gemcitabine, other deoxycytidine analogs that inhibit DNA replication but do not cause strand breaks. Thus, once incorporated into DNA, the CNDAC molecule appears to act by a dual mechanism that 1) delays the progress of further DNA replication, but 2) upon addition of a deoxynucleotide results in the conversion of the incorporated analog to a de facto DNA chain terminator at the 3' terminus of a single strand break. It is likely that DNA strand breaks trigger cell cycle arrest in G(2).
Azuma
A
A
Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Huang
P
P
Matsuda
A
A
Plunkett
W
W
D000970:Antineoplastic Agents / Q000378:metabolism* / Q000494:pharmacology; D016203:CDC2 Protein Kinase / Q000378:metabolism; D019457:Chromosome Breakage / Q000235:genetics; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D003561:Cytarabine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000187:drug effects* / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D012313:RNA / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000093542:Gemcitabine
D000970:Antineoplastic Agents; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D004273:DNA, Neoplasm; D003561:Cytarabine; D003841:Deoxycytidine; C070279:2'-cyano-2'-deoxyarabinofuranosylcytosine; D012313:RNA; D016203:CDC2 Protein Kinase; D000093542:Gemcitabine