Cytidine deaminase genetic variants influence RNA expression and cytarabine cytotoxicity in acute myeloid leukemia.
ABSTRACT Cytidine deaminase (CDA) irreversibly deaminates cytarabine (Ara-C), a key component of acute myeloid leukemia (AML) induction and consolidation therapy. CDA overexpression results in Ara-C resistance, while decreased expression is associated with toxicity. We evaluated factors influencing variation in CDA mRNA expression in adult AML patients and normal controls, and how they contributed to Ara-C cytotoxicity in AML cells.
CDA mRNA expression in 100 de novo AML patients and 36 normal controls were determined using quantitative reverse-transcriptase PCR. Genetic variants in the CDA gene were screened by direct sequencing. IC₅₀ of Ara-C was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.
CDA RNA expression as well as Ara-C IC₅₀ showed wide variation in AML samples and normal controls. Fourteen sequence variants were identified, three of which (-33delC, intron 2 TCAT repeat and the 3´untranslated region 816delC variants) showed significant association with RNA expression and the nonsynonymous coding variant 79A>C was associated with Ara-C cytotoxicity.
CDA genetic variants explain the variation in RNA expression and may be candidates for individualizing Ara-C therapy.
- Pharmacogenomics 02/2013; 14(3):227-30. · 3.86 Impact Factor
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ABSTRACT: Cytidine deaminase (CDA) is the major enzyme involved in metabolism of gemcitabine, a pyrimidine analogue widely used for chemotherapy of solid tumours. While only low amounts of administered gemcitabine undergo intracellular phosphorylation into active forms and involve in antineoplastic activities, majority of it is rapidly inactivated by CDA and excreted to avoid drug toxicity. Knowledge of the genetic polymorphisms mildly effecting cellular activity of the enzyme CDA is therefore crucial to understanding drug-induced toxicities associated with gemcitabine. Functional significance and allele frequencies for common SNPs including 79A>C (*2) and 208G>A (*3) have been reported in various ethnic populations including Caucasian, African, Korean and Japanese. However, such studies have not been reported in any Indian sub-population. In the present study, conventional polymerase chain reaction (PCR) based amplification using gene specific primers and Sanger sequencing were performed to identify CDA variants in 50 healthy individuals from Indian sub-population. Established common variant 79A>C known to reduce CDA activity was observed at a frequency of 0.14 in the study cohort. In addition to other known variants, one novel variant, IVS325-209T>C was detected at a frequency of 0.06. Genetic variants in CDA gene and their frequencies established in our study hold value in pharmacogenetics.Gene 04/2013; · 2.20 Impact Factor
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ABSTRACT: Aim: To assess the distribution of CDA activity from whole blood of 142 healthy subjects, determining its main predictors among genetic (six CDA SNPs) and physiological factors (age and gender). Moreover, we performed a kinetic study of the two CDA protein variants (Q27 and K27) determined by the rs2072671 SNP. Materials & methods: CDA activity was assessed by HPLC. Selected CDA SNPs were genotyped by PCR-based methods. Recombinant CDA protein variants (Q27 and K27) were expressed in an Escherichia coli strain SØ5201 and kinetic assays were performed. Results: The mean value of CDA activity was 0.051 ± 0.024 mU/mg and followed a normal distribution in the study population. Carriers of the CDA*2B (-451T/-92G/-31Del/79C/435C) haplotype displayed higher CDA activity compared with the others. CDA -451G>A, -92A>G and 79A>C (K27Q) SNPs displayed significant associations with CDA activity. The best predictive model of CDA activity included the variables gender and CDA 79A>C (K27Q). Cytidine is the preferential substrate for the variant Q27. Conclusion: We suggest the analysis of both CDA activity and CDA 79A>C (K27Q) SNP in future prospective trials with cytidine analogs, alone or in combination, in order to identify the best marker to secure the administration of these anticancer therapies. Original submitted 22 October 2012; Revision submitted 11 March 2013.Pharmacogenomics 05/2013; 14(7):769-81. · 3.86 Impact Factor