title: Low level of mitochondrial deoxyguanosine kinase is the dominant factor in acquired resistance to 9-beta-D-arabinofuranosylguanine cytotoxicity.
abstract: 9-beta-D-arabinofuranosylguanine (Ara-G) is an important and relatively new guanosiue analog with activity in patients with T-cell malignancies. The biochemical and molecular events leading to resistance to Ara-G are not fully understood. Therefore we generated two Ara-G-resistant human MOLT-4 leukemic cell lines with different levels of resistance. The mitochondrial enzyme deoxyguanosine kinase (dGK) and the nuclear/cytosol enzyme deoxycytidine kinase (dCK) are key enzymes in the activation of Ara-G. Decreased levels of dGK protein and mRNA were found in both resistant cell sublines. The activity of dCK was decreased in the subline with higher resistance to Ara-G and these cells were highly cross-resistant to other nucleosides activated by dCK. Increased activity of the mitochondrial enzyme thymidine kinase 2 was observed in both resistant sublines and this could be related to the dGK deficiency. In search for other resistance mechanisms it was found that the resistant cells overexpress the mdr1 gene, while no changes were detected in the levels of multidrug resistance-associated protein 1 through 6, lung resistance-associated protein or topoisomerase IIalpha or IIbeta. Taken together, our findings demonstrate that multiple mechanisms are involved in the acquired resistance to Ara-G. However, low expression of dGK is the most apparent alteration in both resistant cell lines. Partial deficiency of dCK was found in the subline cells with higher resistance to Ara-G. Furthermore, Ara-G may select for high expression of the multidrug resistance (mdr1) which could be a specific resistance mechanism but more likely part of an overall cellular stress response.
authors.affiliation: Department of Medicine and Care, Division of Clinical Pharmacology, Faculty of Health Sciences, Linköping, SE-581 85, Sweden.
authors.forename: Kourosh
authors.initials: K
authors.lastname: Lotfi
authors.forename: Emma
authors.initials: E
authors.lastname: Månsson
authors.forename: Curt
authors.initials: C
authors.lastname: Peterson
authors.forename: Staffan
authors.initials: S
authors.lastname: Eriksson
authors.forename: Freidoun
authors.initials: F
authors.lastname: Albertioni
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D018943:Anthracyclines / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001087:Arabinonucleosides / Q000096:biosynthesis; D015153:Blotting, Western; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D003630:Daunorubicin / Q000494:pharmacology; D003842:Deoxycytidine Kinase / Q000096:biosynthesis / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005452:Fluoresceins / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D009705:Nucleosides / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018943:Anthracyclines; D000970:Antineoplastic Agents; D001087:Arabinonucleosides; D005452:Fluoresceins; D009705:Nucleosides; D012333:RNA, Messenger; C085925:calcein AM; C028771:9-arabinofuranosylguanine; D016572:Cyclosporine; D017853:Phosphotransferases (Alcohol Group Acceptor); C019165:deoxyguanosine kinase; D003842:Deoxycytidine Kinase; D003630:Daunorubicin