Phenotype-genotype variability in the human CYP3A locus as assessed by the probe drug quinine and analyses of variant CYP3A4 alleles
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm (Sweden)
- Department of Clinical Pharmacology, Faculty of Medicine, Muhimbili University College of Health Sciences, Dar es Salaam (Tanzania)
- Division of Clinical Pharmacology, Department of Medical Laboratory Sciences and Technology, Karolinska Institutet and Hospital Pharmacy, Huddinge University Hospital, Stockholm (Sweden)
The human cytochrome P450 3A (CYP3A) enzymes, which metabolize 50% of currently used therapeutic drugs, exhibit great interindividual differences in activity that have a major impact on drug treatment outcome, but hitherto no genetic background importantly contributing to this variation has been identified. In this study we show that CYP3A4 mRNA and hnRNA contents with a few exceptions vary in parallel in human liver, suggesting that mechanisms affecting CYP3A4 transcription, such as promoter polymorphisms, are relevant for interindividual differences in CYP3A4 expression. Tanzanian (n = 143) healthy volunteers were phenotyped using quinine as a CYP3A probe and the results were used for association studies with CYP3A4 genotypes. Carriers of CYP3A4*1B had a significantly lower activity than those with CYP3A4*1 whereas no differences were seen for five other SNPs investigated. Nuclear proteins from the B16A2 hepatoma cells were found to bind with less affinity to the CYP3A4*1B element around -392 bp as compared to CYP3A4*1. The data indicate the existence of a genetic CYP3A4 polymorphism with functional importance for interindividual differences in enzyme expression.
- OSTI ID:
- 20793198
- Journal Information:
- Biochemical and Biophysical Research Communications, Vol. 338, Issue 1; Other Information: DOI: 10.1016/j.bbrc.2005.09.020; PII: S0006-291X(05)02019-X; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0006-291X
- Country of Publication:
- United States
- Language:
- English
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