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A functional single-nucleotide polymorphism in the human cytidine deaminase gene contributing to ara-C sensitivity
Lijie Yue1, Yutaka Saikawa, Kazuhisa Ota
1Division of Cardiovascular Medicine, Vascular Medicine, Angiogenesis and Vascular Development, Department of Pediatrics, Kanazawa University Graduate School of Medical Science, Ishikawa, Japan.
Abstract:
To test the hypothesis that analyses of drug targets for polymorphism will help to establish gene-based information for the treatment of cancer patients, we investigated the functional single-nucleotide polymorphisms in the human cytidine deaminase (HDCA) gene. The cDNAs from 52 leukaemia/lymphoma samples and 169 control blood samples were direct-sequenced and analysed for the polymorphisms. Three different polymorphisms (A79C, G208A and T435C) were identified in the coding region of the HDCA gene and displayed allelic frequencies of 20.1%, 4.3% and 70.1%, respectively. No association with susceptibility to disease was observed. A novel polymorphism, G208A produced an alanine to threonine substitution (A70T) within the conserved catalytic domain. By introduction of the polymorphic HCDA genes into the yeast CDA-null mutants, the HCDA-70T showed 40% and 32% activity of prototype for cytidine and ara-C substrates, respectively (P < 0.01). The ara-C IC50 value of the yeast transformants carrying HCDA-70T was 757 +/- 33 micromol and was significantly lower (P < 0.01) than that of prototype (941 +/- 58 micromol). This study demonstrated a population characterized with 208A genotype for, which potentially leads one more sensitive to ara-C treatment than prototype. Accumulation of polymorphisms in the genes responsible for drug metabolism and determination of polymorphism-induced biological variations could provide the additional therapeutic strategies in risk-stratified protocols for the treatment of childhood malignancies.
Insights
Investigating human cytidine deaminase (HDCA) gene polymorphisms revealed a novel G208A variant. This variant, HCDA-70T, exhibits reduced enzyme activity, potentially increasing sensitivity to ara-C cancer treatment.
Area of Science:
- Pharmacogenomics
- Molecular Biology
- Cancer Therapeutics
Background:
- Genetic variations in drug-metabolizing enzymes can influence cancer treatment efficacy.
- Understanding gene-based information is crucial for personalized cancer therapy.
Purpose of the Study:
- To investigate functional single-nucleotide polymorphisms (SNPs) in the human cytidine deaminase (HDCA) gene.
- To determine the impact of these polymorphisms on enzyme activity and potential drug response in cancer patients.
Main Methods:
- Direct sequencing of HDCA cDNA from leukemia/lymphoma samples and controls.
- Functional analysis of identified polymorphisms by introducing polymorphic HDCA genes into yeast CDA-null mutants.
- Assessing enzyme activity with cytidine and ara-C substrates and determining IC50 values.
Main Results:
- Three HDCA gene polymorphisms (A79C, G208A, T435C) were identified with specific allelic frequencies.
- A novel G208A polymorphism resulted in an alanine to threonine substitution (A70T) in the catalytic domain.
- The HCDA-70T variant showed significantly reduced activity (40% for cytidine, 32% for ara-C) and a lower IC50 for ara-C in yeast models (P < 0.01).
Conclusions:
- The G208A polymorphism (HCDA-70T) may confer increased sensitivity to ara-C treatment in certain populations.
- Identifying and characterizing gene polymorphisms involved in drug metabolism offers potential for risk-stratified cancer treatment strategies.
- This research supports the development of gene-based therapeutic approaches for childhood malignancies.