title: 2',3'-Dideoxyadenosine is selectively toxic for TdT-positive cells.
abstract: The 2',3'-dideoxynucleosides (ddNs) are currently undergoing clinical evaluation as antiretroviral agents in HIV-infected individuals. When phosphorylated, the ddNs (ddNTPs) function as chain-terminating substrate analogues with reverse transcriptase, thereby inhibiting HIV replication. These nucleoside analogues can also inhibit, by chain-terminating additions, the primitive lymphoid DNA polymerase, terminal deoxynucleotidyl transferase (TdT). To determine the effect of possible intracellular chain-terminating additions of ddNMPs by TdT, we exposed a series of TdT-positive and TdT-negative cell lines to 2',3'-dideoxyadenosine (ddA), a representative ddN. At ddA concentrations 25-fold higher than required for inhibition of HIV replication, progressive dose-related cytotoxicity was observed in the TdT-positive cell lines. This was accentuated by the adenosine deaminase inhibitor Coformycin (CF), presumably by enhancing the intracellular generation of ddATP from ddA. A central role of TdT in mediating the ddA/CF cytotoxicity was suggested by studies in a pre-B-cell line rendered TdT positive by infection with a TdT cDNA-containing retroviral vector. After a 48-hour continuous exposure period to 250 mumol/L ddA and 30 mumol/L CF, 30% cell death was observed in the TdT-negative parental line, whereas 90% cell death was observed in the TdT-positive daughter line. Exposure of fresh TdT-positive leukemic cells to ddA/CF for 72 hours ex vivo resulted in cytotoxicity (six cases of acute lymphocytic leukemia [ALL]) while not affecting TdT-negative acute leukemic cells (six cases). We conclude that ddA/CF selectively damages TdT-positive cells, presumably by chain-terminating additions of ddAMP, and that this may have therapeutic relevance in TdT-positive malignant disease.
authors.affiliation: Evans Department of Clinical Research, Boston University Medical Center, MA 02118.
authors.forename: Z
authors.initials: Z
authors.lastname: Spigelman
authors.forename: R
authors.initials: R
authors.lastname: Duff
authors.forename: G P
authors.initials: GP
authors.lastname: Beardsley
authors.forename: S
authors.initials: S
authors.lastname: Broder
authors.forename: D
authors.initials: D
authors.lastname: Cooney
authors.forename: N R
authors.initials: NR
authors.lastname: Landau
authors.forename: H
authors.initials: H
authors.lastname: Mitsuya
authors.forename: B
authors.initials: B
authors.lastname: Ullman
authors.forename: R
authors.initials: R
authors.lastname: McCaffrey
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003070:Coformycin / Q000494:pharmacology; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004257:DNA Polymerase II / Q000378:metabolism; D003839:Deoxyadenosines / Q000031:analogs & derivatives* / Q000633:toxicity; D016048:Dideoxyadenosine; D004720:Endonucleases / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D013379:Substrate Specificity
chemical_list: D003839:Deoxyadenosines; D003070:Coformycin; D016048:Dideoxyadenosine; D004254:DNA Nucleotidyltransferases; D004253:DNA Nucleotidylexotransferase; D004257:DNA Polymerase II; D004720:Endonucleases