title: 2', 3'-Dideoxycytidine represses thymidine kinases 1 and 2 expression in T-lymphoid cells.
abstract: In vitro culture of H9 human lymphoid cells in the presence of 5.0 microM dideoxycytidine (ddC), for about 40-45 days, selected cells (H9-ddC cells), which were resistant to the drug and cross-resistant to AZT (zidovudine) and 5-fluoro-2'-deoxyuridine (FdUR). The major mechanism of cross-resistance to AZT and FdUR in these cells was low cellular activity of thymidine kinase (TK). To explore molecular mechanisms of the reduced TK activity in H9-ddC cells, the mRNA expression of TK1 and TK2 and western blot analysis of TK1 protein were performed. RT-PCR analysis revealed that in H9-ddC cells the expression of both TK1 and TK2 mRNA was reduced to 27.1% and 79.4%, respectively. The reduced TK1 gene expression was confirmed by an absence of a detectable TK1 protein band in western blot of H9-ddC cells. These results demonstrate that long-term treatment of H9 cells in the presence of ddC down-regulated TK1 and TK2 gene expression and reduced the expression and activity of TK in the resistant cells.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine (M862), P.O. Box 019132, University of Miami School of Medicine, Miami, FL 33101, USA.
authors.forename: Tieran
authors.initials: T
authors.lastname: Han
authors.forename: Marilyn
authors.initials: M
authors.lastname: Fernandez
authors.forename: Malancha
authors.initials: M
authors.lastname: Sarkar
authors.forename: Ram P
authors.initials: RP
authors.lastname: Agarwal
mesh_terms: D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology*; D015153:Blotting, Western; D002478:Cells, Cultured; D003561:Cytarabine / Q000378:metabolism / Q000494:pharmacology; D017931:DNA Primers / Q000737:chemistry; D015536:Down-Regulation / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism; D016047:Zalcitabine / Q000378:metabolism / Q000494:pharmacology*; D015215:Zidovudine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D019380:Anti-HIV Agents; D017931:DNA Primers; D012333:RNA, Messenger; D003561:Cytarabine; D015215:Zidovudine; D016047:Zalcitabine; C105339:thymidine kinase 2; D013937:Thymidine Kinase; C092717:thymidine kinase 1