Resistance to cytarabine and gemcitabine and in vitro selection of transduced cells after retroviral expression of cytidine deaminase in human hematopoietic progenitor cells

University of Duisburg-Essen, Essen, North Rhine-Westphalia, Germany
Leukemia (Impact Factor: 10.43). 01/2006; 19(12):2281-8. DOI: 10.1038/sj.leu.2403977
Source: PubMed


Overexpression of the detoxifying enzyme cytidine deaminase (CDD) renders normal and leukemic hematopoietic cells resistant to cytarabine (1-beta-D-arabinofuranosylcytosine), and studies on murine cells have suggested transgenic CDD overexpression as a way to reduce the substantial myelotoxicity induced by the deoxycytidine analogs cytarabine and gemcitabine (2',2'-difluorodeoxycytidine). We now have investigated CDD (over-)expression in the human hematopoietic system. Retroviral gene transfer significantly increased the resistance of CDD-transduced cord blood and peripheral blood-derived progenitor cells for doses ranging from 20-100 nM cytarabine and 8-10 nM gemcitabine. Protection was observed for progenitors of erythroid as well as myeloid differentiation, though the degree of protection varied for individual drugs. In addition, significant selection of CDD-transduced cells was obtained after a 4-day culture in 30-100 nM cytarabine. Thus, our data demonstrate that overexpression of CDD cDNA results in significant protection of human progenitors from cytarabine- as well as gemcitabine-induced toxicity, and allows in vitro selection of transduced cells. This strongly argues for a potential therapeutic role of CDD gene transfer in conjunction with dose-intensive cytarabine- or gemcitabine-containing chemotherapy regimen.

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Available from: Walter Bardenheuer, Sep 17, 2014
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    • "CDA is the enzyme that catabolizes gemcitabine to dFdU, preventing the stepwise conversion of gemcitabine into dFdCMP, dFdCDP and dFdCTP and inhibiting DNA synthesis. Previous study has revealed the function of CDA in gemcitabine resistance (26). Another important enzyme involved in gemcitabine metabolism is RNR. "
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    ABSTRACT: Liver kinase B1 (LKB1) is a well-known tumor suppressor gene in a variety of human cancers, including breast cancer. However, its role in gemcitabine resistance is unclear. Since gemcitabine in combination with other chemotherapeutic reagents is the first-line treatment in advanced breast cancer, the aim of the present study was to determine the effect of ectopic expression of LKB1 on chemosensitivity to gemcitabine in the breast cancer MDA-MB-231 cell line. Increasing the expression of LKB1 was found to directly correlate with gemcitabine chemoresistance. Although LKB1 suppressed the cell proliferation rate and clonogenicity in the absence of gemcitabine, it increased the median inhibitory concentration of gemcitabine and clonogenicity of cells in the presence of gemcitabine. Mechanistic analysis indicated that LKB1 was able to protect cells from DNA damage caused by gemcitabine. Furthermore, it was found that LKB1 induced a significant upregulation of cytidine deaminase expression, an important enzyme that accelerates gemcitabine catabolization. Overall, dual characteristics of LKB1 were identified: Suppressing cell growth in normal conditions and enhancing chemoresisitance to gemcitabine, possibly by accelerating degradation of gemcitabine, and protecting cells from DNA damage caused by gemcitabine.
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    • "For instance, cytarabine (also known as AraC), a nucleoside drug widely used for the treatment of acute myelogenous leukemia (Sampath et al., 2006), necessitates initial phosphorylation by deoxycytidine kinase to cytarabine-monophosphate which is subsequently phosphorylated to the active form cytarabine triphosphate. To circumvent the effects of these drugs, cancer cells develop resistance through decreased drug activation (Kufe and Spriggs, 1985; Bardenheuer et al., 2005). This occurs via the downregulation or mutation of enzymes involved in this metabolic pathway, such as deoxycytidine kinase in the case of cytarabine (Sampath et al., 2006). "
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    • "A better understanding of these mechanisms will play an important role in overcoming gemcitabine resistance and help combat a bleak survival rate. Some studies have shown that gemcitabine resistance is associated with cytidine deaminase (CDA) [6]–[8]. CDA is the catabolic enzyme of gemcitabine which eventually transforms it to an inactive metabolite (2′,2′-difluorodeoxyuridine). "
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    ABSTRACT: Tetrahydrouridine (THU) is a well characterized and potent inhibitor of cytidine deaminase (CDA). Highly expressed CDA catalyzes and inactivates cytidine analogues, ultimately contributing to increased gemcitabine resistance. Therefore, a combination therapy of THU and gemcitabine is considered to be a potential and promising treatment for tumors with highly expressed CDA. In this study, we found that THU has an alternative mechanism for inhibiting cell growth which is independent of CDA expression. Three different carcinoma cell lines (MIAPaCa-2, H441, and H1299) exhibited decreased cell proliferation after sole administration of THU, while being unaffected by knocking down CDA. To investigate the mechanism of THU-induced cell growth inhibition, cell cycle analysis using flow cytometry was performed. This analysis revealed that THU caused an increased rate of G1-phase occurrence while S-phase occurrence was diminished. Similarly, Ki-67 staining further supported that THU reduces cell proliferation. We also found that THU regulates cell cycle progression at the G1/S checkpoint by suppressing E2F1. As a result, a combination regimen of THU and gemcitabine might be a more effective therapy than previously believed for pancreatic carcinoma since THU works as a CDA inhibitor, as well as an inhibitor of cell growth in some types of pancreatic carcinoma cells.
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