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Biochemical Pharmacology and Resistance to 2-Chloro-2′-arabino-fluoro-2′-deoxyadenosine, a Novel Analogue of Cladribine in Human Leukemic Cells
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University of Medicine, Budapest, Hungary.
Linköping University, Department of Medicine and Care, Clinical Pharmacology. Linköping University, Faculty of Health Sciences.
Department of Clinical Oncology, Karolinska Hospital, Stockholm, Sweden.
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1999 (English)In: Clinical Cancer Research, ISSN 1078-0432, E-ISSN 1557-3265, Vol. 5, no 9, 2438-2444 p.Article in journal (Refereed) Published
Abstract [en]

The objective of the present study was to investigate the biochemical pharmacology of 2-chloro-2′-arabino-fluoro-2′-deoxyadenosine (CAFdA) — a fluorinated analogue of cladribine [2-chloro-2′-deoxyadenosine, Leustatin (CdA)] with improved acid and metabolic stability — in human leukemic cell lines and in mononuclear cells isolated from patients with chronic lymphocytic leukemia (CLL) and acute myelocytic leukemia (AML). We have also made and characterized two cell lines that are not sensitive to the growth inhibitory and cytotoxic effects of CAFdA. Incubation of cells isolated from the blood of CLL and AML patients with various concentrations of CdA or of CAFdA accumulated CdA and CAFdA nucleotides in a dose-dependent manner. A significantly higher rate of phosphorylation to monophosphates was observed for CAFdA than for CdA in cells from CLL patients (n = 14; P = 0.04). The differences in the phosphorylation were even more pronounced for the respective triphosphates in both CLL (n = 14; P = 0.001) and AML (n = 4; P = 0.04) cells. Retention of CAFdA 5′-triphosphate (CAFdATP) was also longer than that for CdA 5′-triphosphate (CdATP) in cells from leukemic patients. The relative efficacy of CAFdA as a substrate for purified recombinant deoxycytidine kinase (dCK), the key enzyme in the activation of nucleoside analogues, was very high and exceeded that of CdA as well as the natural substrate, deoxycytidine, by a factor of 2 and 8, respectively. The Km for CAFdA with dCK was also lower than that for CdA, as measured in crude extracts from the human acute lymphoblastic leukemia cell line CCRF-CEM and the promyelocytic leukemia cell line HL60. Acquired resistance to CAFdA in HL60 and in CCRF-CEM cell lines was directly correlated to the decreased activity of the nucleoside phosphorylating enzyme, dCK. Resistant cells also showed a considerable degree of cross-resistance to analogues that were activated by dCK. These observations demonstrated that dCK phosphorylates CAFdA more efficiently than CdA. Furthermore, CAFdATP is apparently more stable than CdATP and the mechanisms of resistance to CAFdA are similar to those leading to CdA resistance. These results encourage studies on the clinical effect of CAFdA in lymphoproliferative diseases.

Place, publisher, year, edition, pages
1999. Vol. 5, no 9, 2438-2444 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-27106Local ID: 11753OAI: oai:DiVA.org:liu-27106DiVA: diva2:247657
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Pharmacology and resistance mechanisms of nucleoside analogues and topoisomerase II interactive agents: studies on human leukemia cells with a focus on cross-resistance
Open this publication in new window or tab >>Pharmacology and resistance mechanisms of nucleoside analogues and topoisomerase II interactive agents: studies on human leukemia cells with a focus on cross-resistance
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this thesis was to elucidate mechanisms of action and resistance of clinically relevant nucleoside analogues and topoisomerase interactive agents in human leukemia cell lines and leukernia cells isolated from peripheral blood of leukemia patients. Interactions and cross-resistance patterns of these different cytotoxic drug families were also studied since these drugs are usually administrated in combination in the clinic.

Two novel nucleoside analogues, clofarabine (2-chloro-2'-arabino-fluoro 2'-deoxyadenosine, CAFdA) and nelarabine (9-ß-D-arabinofuranosylguanine, AraG) were studied regarding cellular activation and mechanisms of resistance. Compared to cladribine (2-chloro- 2'-deoxyadenosine, CdA), CAFdA was more effective due to better stability and more efficient phosphorylation by deoxycytidine kinase (dCK). The mechanism of resistance to CAFdA was decreased activity of dCK. The most important mechanism contributing to resistance to AraG seems to be the deficiency of the activating enzymes dCK and deoxyguanosine kinase (dGK), as measured by enzyme activity assays, Western blotting, and real-time polymerase chain reaction. Unexpected cross-resistance between topoisomerase interactive agents and nucleoside analogues was identified in CEM and MOLT-4 cell lines developed for resistance to etoposide (VP) and AraG, respectively, by means of a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide viability assay. Resistance to VP was due to a decrease in the activity and amount of topoisomerase TI. Major cause of resistance to the nucleoside analogues CdA and AraC was metabolic alterations producing increased activity of 5'-nucleotidase and higher level of endogenous deoxycytidine triphosphate. The AraG-resistant cells showed also classical multidrug resistance (MDR) phenomena. The accumulation and cytotoxicity of daunorubicin (Dnr) were studied in AraG-resistant cells and in response to the resistance modifiers, such as cyclosporin A. The level of mdr1 mRNA and its product, P-glycoprotein, was increased. The topoisomerase interactive agent, idarubicin (Ida), a semisynthetic derivative of Dnr, was more effective in inducing apoptosis as determined by the Annexin V -FITC method, and Ida-resistant cells did not show any classical MDR phenomena.

Thus, these studies suggest that anticancer agents from the same class of cytostatics could have important differences in effectivity and mechanisms of resistance. These results confirm the possibility of coexpression of multiple mechanisms of resistance in human leukemic cells, which have been selected by exposure to a single-dmg. The generally assumed lack of crossresistance between nucleoside analogues and topoisomerase interactive agents is questionable.

The rationale for combination therapy should be based on biological properties and cross-resistance analyses of the included drugs.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2001. 75 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 698
Keyword
Nucleoside analogue, cross-resistance, multidrug resistance, deoxycytidine kinase, leukemia, anthracyclines, P-glycoprotein
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-27518 (URN)12174 (Local ID)91-7373-140-4 (ISBN)12174 (Archive number)12174 (OAI)
Public defence
2001-11-16, Berzeliussalen, Universitetssjukhuset, Linköping, 13:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-11-02Bibliographically approved

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