Selection of the Best Blood Compartment to Measure Cytidine Deaminase Activity to Stratify for Optimal Gemcitabine or Cytarabine Treatment |
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Authors: | Godefridus J. Peters Richard J. Honeywell Marie Maulandi Elisa Giovannetti Nienke Losekoot Marie-Christine Etienne-Grimaldi |
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Affiliation: | 1. Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlandsgj.peters@vumc.nl;3. Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands;4. Transfer Oncology Laboratory, Aix-Marseille University, Marseille, France;5. Laboratoire d’Oncopharmacologie, Centre Antoine Lacassagne, Nice, France |
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Abstract: | Cytidine deaminase (CDA) plays a crucial role in the degradation of cytidine analogs, such as gemcitabine and cytarabine. Several studies showed that a low CDA activity is associated with more toxicity but a higher efficacy, while a high activity will lead to a lower efficacy but less toxicity. A stratified dosing strategy based on the relative CDA activity would increase efficiency. In order to predict these events, a reliable measurement of CDA with a validated method is crucial. We aimed to determine which phenotype assay would be most suitable; a spectrophotometric assay using cytidine as a substrate, or an HPLC assay using gemcitabine as a substrate. In serum and whole blood of 26 volunteers, both assays showed an excellent correlation (R > 0.999), but not in plasma nor in red blood cells. Moreover, there was no difference between males and females.In conclusion, the spectrophotometric assay seems the most simple and cost-effective test. It should be performed in serum, while it should be normalized on protein content as measured by the Bicinchoninic Acid. |
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Keywords: | Cytidine deaminase gemcitabine cytarabine protein assays |
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