Molecular functionality of CYP2C9 polymorphisms and their influence on drug therapy

Balasmeh

Libyan Journal of Medicine

2017

Self Cite

The present study aimed to identify the NAT2 haplotypes, linkage disequilibrium, and novel NAT2 genetic variants among Jordanian population. We isolated the genomic DNA from 68 healthy, Arab, unrelated Jordanian volunteers to amplify the protein-coding region of NAT2 gene by polymerase chain reaction (PCR). Then, the amplified PCR products were sequenced using Applied Biosystems Model (ABI3730x1). It is found that the allele frequencies of known NAT2 genetic variants 191G>A, 282C>T, 341T>C, 481C>T, 590G>A, and 803A>G were 0.7, 26.5, 48.5, 35.3, 30.9, and 32.4%, respectively. The NAT2 allele frequencies were generally similar to those of white Europeans but different from those of Asian and African populations. The most common NAT2 haplotype was NAT2*5B with a frequency of 29.3%. According to the NAT2 haplotype frequencies, 72% (95% confidence interval 61.4–82.7%) of the volunteers were slow encoding NAT2 haplotype acetylators. The NAT2*5 represented variants 341T>C and 481C>T were in strong but not complete linkage disequilibrium (D′ = 0.8, r 2 = 0.63). In addition, this study found a novel nonsynonymous NAT2 436G>A genetic variant with low frequency (0.7%). However, this novel variant was predicted to be tolerated and not harmful to the NAT2 protein, using in silico prediction tools. It is concluded that the frequency of slow encoding NAT2 haplotype was high among Jordanian volunteers, which may have effects on drug responses and susceptibility to some diseases, such as cancers.

Section: Discussionmentioning

confidence: 99%

Sequence analysis of theN-acetyltransferase 2 gene (NAT2) among Jordanian volunteers

Balasmeh

Libyan Journal of Medicine

2017

Self Cite

“…Despite efforts to understand the effects of MDR1 polymorphisms on pharmacokinetics, no consensus has been reached on this issue because of the lack of a humanized animal model. Regarding the CYP2C family, the effects of CYP2C9 and CYP2C19 polymorphisms on metabolic activity toward drugs that are known substrates of these proteins have been reported 34 , 35 . Polymorphisms in UGT2 genes have also been reported to affect expression and metabolic activity 36 .…”

Section: Discussionmentioning

confidence: 99%

Modification of single-nucleotide polymorphism in a fully humanized CYP3A mouse by genome editing technology

Abe

Kobayashi

Oji

et al. 2017

Sci Rep

Cytochrome P450, family 3, subfamily A (CYP3A) enzymes metabolize approximately 50% of commercially available drugs. Recently, we developed fully humanized transchromosomic (Tc) CYP3A mice with the CYP3A cluster including CYP3A4, CYP3A5, CYP3A7, and CYP3A43. Our humanized CYP3A mice have the CYP3A5*3 (g.6986G) allele, resulting in the almost absence of CYP3A5 protein expression in the liver and intestine. To produce model mice for predicting CYP3A5′s contribution to pharmacokinetics, we performed a single-nucleotide polymorphism (SNP) modification of CYP3A5 (g.6986G to A, *3 to *1) on the CYP3A cluster using genome editing in both mouse ES cells and fertilized eggs, and produced humanized CYP3A5*1 mice recapitulating the CYP3A5*1 carrier phenotype in humans. The humanized CYP3A mouse with CYP3A5*1 is the first Tc mouse for predicting the SNP effect on pharmacokinetics in humans. The combination of Tc technology and genome editing enables the production of useful humanized models that reflect humans with different SNPs.

Pharmacology Res & Perspec

“…). Published discrepancies in variant CYP2C9 activity are common and likely arise from variations in experimental procedures between laboratories (Jarrar and Lee ).…”

Section: Discussionmentioning

confidence: 99%

“…In silico analyses by Matimba et al (2009) significant correlation between the CYP2C9*9 allele and phenytoin metabolism was not detected in African epilepsy patients (Matimba et al 2009). Published discrepancies in variant CYP2C9 activity are common and likely arise from variations in experimental procedures between laboratories (Jarrar and Lee 2014).…”

mentioning

confidence: 99%

In vitro metabolism of exemestane by hepatic cytochrome P450s: impact of nonsynonymous polymorphisms on formation of the active metabolite 17β‐dihydroexemestane

Peterson

Xia

Chen

et al. 2017

Exemestane (EXE) is an endocrine therapy commonly used by postmenopausal women with hormone‐responsive breast cancer due to its potency in inhibiting aromatase‐catalyzed estrogen synthesis. Preliminary in vitro studies sought to identify phase I EXE metabolites and hepatic cytochrome P450s (CYP450s) that participate in EXE biotransformation. Phase I metabolites were identified by incubating EXE with HEK293‐overexpressed CYP450s. CYP450s 1A2, 2C8, 2C9, 2C19, 2D6, 3A4, and 3A5 produce 17β‐dihydroexemestane (17β‐DHE), an active major metabolite, as well as two inactive metabolites. 17β‐DHE formation in pooled human liver microsomes subjected to isoform‐specific CYP450 inhibition was also monitored using tandem mass spectrometry. 17β‐DHE production in human liver microsomes was unaffected by isoform‐specific inhibition of CYP450s 2A6, 2B6, and 2E1 but decreased 12–39% following inhibition of drug‐metabolizing enzymes from CYP450 subfamilies 1A, 2C, 2D, and 3A. These results suggest that redundancy exists in the EXE metabolic pathway with multiple hepatic CYP450s catalyzing 17β‐DHE formation in vitro. To further expand the knowledge of phase I EXE metabolism, the impact of CYP450 genetic variation on 17β‐DHE formation was assessed via enzyme kinetic parameters. Affinity for EXE substrate and enzyme catalytic velocity were calculated for hepatic wild‐type CYP450s and their common nonsynonymous variants by monitoring the reduction of EXE to 17β‐DHE. Several functional polymorphisms in xenobiotic‐metabolizing CYP450s 1A2, 2C8, 2C9, and 2D6 resulted in deviant enzymatic activity relative to wild‐type enzyme. Thus, it is possible that functional polymorphisms in EXE‐metabolizing CYP450s contribute to inter‐individual variability in patient outcomes by mediating overall exposure to the drug and its active metabolite, 17β‐DHE.