CYP2D6*4 allele and breast cancer risk: is there any association?

Explore the distribution of (rs35742686, rs3892097 and rs1065852) genetic polymorphisms of cytochrome P4502D6 gene in the Moroccan population

Background

The CYP2D6 gene encodes a crucial enzyme involved in the metabolic pathways of many commonly used drugs. It is a highly polymorphic gene inducing an interethnic and interindividual variability in disease susceptibility and treatment response. The aim of this study is to evaluate the frequency of the three CYP2D6 most investigated alleles (CYP2D6*3, CYP2D6*4, and CYP2D6*10 alleles) in Morocco compared to other populations.

This study enrolled 321 healthy Moroccan subjects. CYP2D6 genotypes and allele frequencies were assessed using a restriction fragment length polymorphism–polymerase chain reaction genotyping method. The Principal Component Analysis (PCA) and dendrogram were conducted to evaluate genetic proximity between Moroccans and other populations depending on CYP2D6 allele frequencies.

Results

According to the current study, the results observed the homozygous wild type of the three studied SNPs were predominant among the Moroccan population, while 1.4% of Moroccans carried the CYP2D6*4 allele responsible for a Poor Metabolizer phenotype and associated with low enzyme activity which may induce a treatment failure. The PCA and cluster dendrogram tools revealed genetic proximity between Moroccans and Mediterranean, European and African populations, versus a distancing from Asian populations.

Conclusion

The distribution of CYP2D6 polymorphisms within Morocco follows the patterns generally found among the Mediterranean, European and African populations. Furthermore, these results will help to lay a basis for clinical studies, aimed to introduce and optimize a personalized therapy in the Moroccan population.

The Association of CYP2D6*4 and POR*28 Polymorphisms on Mirtazapine Plasma Level in Subjects with Major Depressive Disorder and Anxiety Disorders

AIMS AND OBJECTIVE

The plasma level of mirtazapine (MIR) varies between individuals primarily depending on the differences in metabolism during pharmacotherapy. CYP2D6 takes the role as a major enzyme in MIR metabolism and POR enzyme donates an electron to CYP2D6 for its activity. Single nucleotide polymorphisms in the genes encoding pharmacokinetic enzymes may cause changes in enzyme activity, leading to differences in metabolism of the drug. Our aim was to assess the influence of CYP2D6*4 and POR*28 polymorphisms on MIR plasma levels in Turkish psychiatric patients.

MATERIALS AND METHODS

The association between genetic variations and plasma level of MIR was investigated on 54 patients. CYP2D6*4 and POR*28 polymorphisms were analysed using Polymerase Chain Reaction- Restriction Fragment Length Polymorphism (PCR-RFLP) and plasma MIR levels were measured using HPLC.

RESULTS

Allele frequencies of CYP2D6*4 and POR*28 were 0.11 and 0.39, respectively in the study population. The results showed that CYP2D6*4 allele carriers have higher C/D MIR levels while POR*28 allele carriers have lower C/D MIR levels. Combined genotype analyses also revealed that individuals with CYP2D6*1/*1 - POR*28/*28 genotype have a statistically lower C/D MIR level (0.95 ng/ml/dose) when compared with individuals with CYP2D6*1/*1 - POR*1/*1 genotype (1.52 ng/ml/dose).

CONCLUSION

Our results indicate that CYP2D6*4 and POR*28 polymorphisms may have a potential in the explanation of differences in plasma levels in MIR treated psychiatric patients. A combination of these variations may be beneficial in increasing drug response and decreasing adverse drug reactions in MIR psychopharmacotherapy.

Polymorphic cytochrome P450 enzymes (CYPs) and their role in personalized therapy

The cytochrome P450 (CYP) enzymes are major players in drug metabolism. More than 2,000 mutations have been described, and certain single nucleotide polymorphisms (SNPs) have been shown to have a large impact on CYP activity. Therefore, CYPs play an important role in inter-individual drug response and their genetic variability should be factored into personalized medicine. To identify the most relevant polymorphisms in human CYPs, a text mining approach was used. We investigated their frequencies in different ethnic groups, the number of drugs that are metabolized by each CYP, the impact of CYP SNPs, as well as CYP expression patterns in different tissues. The most important polymorphic CYPs were found to be 1A2, 2D6, 2C9 and 2C19. Thirty-four common allele variants in Caucasians led to altered enzyme activity. To compare the relevant Caucasian SNPs with those of other ethnicities a search in 1,000 individual genomes was undertaken. We found 199 non-synonymous SNPs with frequencies over one percent in the 1,000 genomes, many of them not described so far. With knowledge of frequent mutations and their impact on CYP activities, it may be possible to predict patient response to certain drugs, as well as adverse side effects. With improved availability of genotyping, our data may provide a resource for an understanding of the effects of specific SNPs in CYPs, enabling the selection of a more personalized treatment regimen.

Relationship between genotypes Sult1a2 and Cyp2d6 and tamoxifen metabolism in breast cancer patients

Tamoxifen is a pro-drug widely used in breast cancer patients to prevent tumor recurrence. Prior work has revealed a role of cytochrome and sulfotransferase enzymes in tamoxifen metabolism. In this descriptive study, correlations were examined between concentrations of tamoxifen metabolites and genotypes for CYP2D6, CYP3A4, CYP3A5, SULT1A1, SULT1A2 and SULT1E1 in 135 patients with estrogen receptor-positive breast cancer. Patients were genotyped using the Roche-AmpliChip® CYP450 Test, and Real-Time and conventional PCR-RFLP. Plasma tamoxifen, 4-hydroxy-tamoxifen, N-desmethyl-tamoxifen, endoxifen and tamoxifen-N-oxide were isolated and quantified using a high-pressure liquid chromatography-tandem mass spectrometry system. Significantly higher endoxifen levels were detected in patients with the wt/wt CYP2D6 compared to the v/v CYP2D6 genotype (p<0.001). No differences were detected in the remaining tamoxifen metabolites among CYP2D6 genotypes. Patients featuring the SULT1A2*2 and SULT1A2*3 alleles showed significantly higher plasma levels of 4-hydroxy-tamoxifen and endoxifen (p = 0.025 and p = 0.006, respectively), as likely substrates of the SULT1A2 enzyme. Our observations indicate that besides the CYP2D6 genotype leading to tamoxifen conversion to potent hydroxylated metabolites in a manner consistent with a gene-dose effect, SULT1A2 also seems to play a role in maintaining optimal levels of both 4-hydroxy-tamoxifen and endoxifen.