Association of CYP2D6 and CYP2C19 polymorphisms and disease-free survival of Thai post-menopausal breast cancer patients who received adjuvant tamoxifen

Pharmacogenomics in Asians: Differences and similarities with other human populations

INTRODUCTION

Various pharmacogenomic (PGx) variants differ widely in different ethnicities. and clinical outcomes associated with these variants may also be substantially varied. Literature was searched in different databases, i.e. PubMed, ScienceDirect, Web of Science, and PharmGKB, from inception to 30 June 2022 for this review.

AREAS COVERED

Certain PGx variants were distinctly varied in Asian populations compared to the other human populations, e.g. CYP2C19*2,*3,*17; CYP2C9*2,*3; CYP2D6*4,*5,*10,*41; UGT1A1*6,*28; HLA-B*15:02, HLA-B*15:21, HLA-B*58:01, and HLA-A*31:01. However, certain other variants do not vary greatly between Asian and other ethnicities, e.g. CYP3A5*3; ABCB1, and SLCO1B1*5. As evident in this review, the risk of major adverse cardiovascular events (MACE) was much stronger in Asian patients taking clopidogrel and who inherited the CYP2C19 loss-of-function alleles, e.g. CYP2C19*2 and*3, when compared to the western/Caucasian patients. Additionally, the risk of carbamazepine-induced severe cutaneous adverse drug reactions (SCARs) for the patients inheriting HLA-B*15:02 and HLA-B*15:21 alleles varied significantly between Asian and other ethnicities. In contrast, both Caucasian and Asian patients inheriting the SLCO1B1*5 variant possessed a similar magnitude of muscle toxicity, i.e. myopathy.

EXPERT OPINION

Asian countries should take measures toward expanding PGx research, as well as initiatives for the purposes of obtaining clinical benefits from this newly evolving and economically viable treatment model.

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.

Resolving discordant CYP2D6 genotyping results in Thai subjects: platform limitations and novel haplotypes

Aim: Several CYP2D6 Luminex xTAG genotype calls were identified as inconsistent or suspicious among Thai subjects and further characterized to identify the root causes. Material & methods: Forty-eight subjects were followed-up with long-range-PCR, quantitative copy number assays and/or Sanger sequencing. Results: Most of the Luminex-duplication calls were either negative or had hybrid structures involving CYP2D6*36 in various configurations. Ten samples were inaccurately called as CYP2D6*2, *29 or *35 alleles. Sequencing revealed three novel haplotypes, CYP2D6*142, *143 and *144 of which two are nonfunctional. Conclusion: The Luminex platform produced a relatively high number of false genotype calls for Thai subjects. Our findings underscore the need for the systematic characterization of the CYP2D6 locus in diverse populations and rigorous platform validation.

Pharmacogenetics of tamoxifen therapy in Asian populations: from genetic polymorphism to clinical outcomes

BACKGROUND

Compared with western countries, Asian breast cancer patients have unique pathological and biological characteristics. Most of them are premenopausal women with HR positive. Tamoxifen as the first-line drug for premenopausal women with HR+ is involved in multiple enzymes and transporters during metabolizing and transporting process. Variants that cause decreased or inactive gene products leading to abnormal responses in tamoxifen therapy have well been studied in western countries, whereas such information is much less reported in Asian populations.

OBJECTIVE

In order to elucidate the relationship between genetic variants and tamoxifen-induced individual drug reactions in different Asian populations and further identify genotypes/phenotypes with potential therapeutic significance.

METHODS

We reviewed the frequencies of genetic variants in major enzymes and transporter genes involved in the metabolism and transport of tamoxifen across Asian populations as well as significant correlations between genotypes/metabolic phenotypes and metabolites concentrations or BC clinical outcomes.

RESULTS

Significant inter-ethnic differences in allele frequencies was found among Asian populations, such as CYP2D6*4, *10, *41, CYP2C9*2, ABCB1 C3435T and SLCO1B1*5, and CYP2D6*10/*10 is the most common genotype correlated with adverse clinical outcomes. Moreover, we summarized the barriers and controversies of implementing pharmacogenetics in tamoxifen therapy and concluded that more population-specific pharmacogenetic studies are needed in the future.

CONCLUSION

This review revealed more systematic pharmacogenomics of genes involved in the metabolism and transport besides CYP2D6, are required to optimize the genotyping strategies and guide the personalized tamoxifen therapy in Asian populations.

Association of CYP gene polymorphisms with breast cancer risk and prognostic factors in the Jordanian population

Background

Single nucleotide polymorphisms (SNPs) in several CYP genes have been associated with altered breast cancer (BC) risk in different populations. Despite this, there is a dearth of information on the roles of these SNPs in Jordanian BC patients. Therefore, this study aims to determine if there is any single nucleotide polymorphism (SNP) within CYP19A1, CYP2C19, CYP2C9, CYP1B1, CYP3A4, and CYP1A2 genes associated with BC in the Jordanian population. In addition, this work investigates the association between selected BC prognostic factors and variants of the aforementioned CYP candidate genes.

Methods

Blood samples were withdrawn from 221 BC patients and 218 healthy volunteers recruited from the Jordanian population. Genomic DNA was withdrawn and, after quantification and quality control, was genotyped using the Sequenom MassARRAY® system (iPLEX GOLD). Statistical analysis was then carried out to assess allelic and genotypic frequencies as well as genetic association between cases and controls.

Results

The CYP19A1 SNP rs7176005 (p < 0.0045) and the CYP1A2 SNP rs762551 (p = 0.004) were significantly associated with BC risk. However, no such association was found for the screened SNPs of the CYP2C9, CYP1B1, CYP2C19 and CYP3A4 genes. Regarding the prognostic factors of BC, several of the screened SNPs were associated with different pathological and clinical features.

Conclusions

Certain CYP genes, particularly CYP19A1 and CYP1A2, were associated with BC risk and development in the Jordanian population.

Real time PCR detection of common CYP2D6 genetic variants and its application in a Karen population study

BACKGROUND

Plasmodium vivax malaria is characterized by relapses arising from the hypnozoite stages in the liver. The only currently registered drug for radical treatment to prevent relapse is primaquine. Primaquine, a prodrug, requires metabolism through the liver cytochrome CYP2D6 isoenzyme to its active metabolite. Mutations in the CYP2D6 gene may thus affect primaquine efficacy. A SNPs genotyping technique was developed to characterize the CYP2D6 genetic variants and tested this in the patients with Plasmodium vivax infection collected in a Karen population on the Thailand-Myanmar border, where P. vivax malaria is endemic.

METHODS

Direct sequencing of PCR-reamplified products (DSP) was used to uncover exonic CYP2D6 sequence variations. Subsequently, an allele-specific oligonucleotide probe real-time SNPs genotyping (ASO) assay was developed for rapid detection of the four clinically relevant CYP2D6 variants occurring in this population. These two in-house developed assays were used to genotype CYP2D6 mutations in blood samples obtained from 70 Karen adults.

RESULTS

Results showed a high degree of concordance between the DSP and ASO methods. Six CYP2D6 point mutations were identified within the Karen population: C100T, C1039T, G1661C, G1846A, C2850T and G4180C, at frequencies of 0.43, 0.43, 0.76, 0.02, 0.32 and 0.76, respectively. The CYP2D6*2, *4, *5, *10 and *36 allelic frequencies were 0.33, 0.02, 0.03, 0.40 and 0.01, respectively. Alleles conferring an intermediate CYP2D6 metabolizer phenotype comprised 46% of the total number of alleles.

CONCLUSION

The newly developed ASO assay is a reliable and rapid tool for large-scale CYP2D6 genotyping. The high frequency of the CYP2D6*10 allele in the Karen population warrants further assessment of its association with the radical curative efficacy of primaquine.

The effect of CYP2D6 *10 polymorphism on adjuvant tamoxifen in Asian breast cancer patients: a meta-analysis

Objective

To evaluate the effect of CYP2D6 *10 polymorphism (C 100C>T, rs1065852) on clinical outcomes of female Asian breast cancer patients with tamoxifen adjuvant treatment.

Methods

Meta-analysis of retrospective cohort studies published in July 2017 was performed. Fifteen studies with 1,794 Asian breast cancer patients were included, using strict eligibility requirements. Associations of disease-free survival (DFS), overall survival (OS) and recurrence rate after tamoxifen intake, with CYP2D6 *10 polymorphism were investigated through random effects models.

Results

CYP2D6 *10 polymorphism was found to have effect on DFS and recurrence rate in various comparison models, but not on overall survival in the female Asian breast cancer patients.

Conclusion

In conclusion, our meta-analysis suggests that significant association of *10/*10 (TT) genotype with poorer DFS and recurrence exists in female Asian breast cancer patients with tamoxifen 20 mg/day adjuvant treatment. In the future, large and well-designed studies are required to illustrate the interactions of CYP2D6 genetic variants, including *10 polymorphism and tamoxifen response on female breast cancer patients.

CYP2C19*2 and CYP2C19*17 variants and effect of tamoxifen on breast cancer recurrence: Analysis of the International Tamoxifen Pharmacogenomics Consortium dataset

The role of cytochrome P450 drug metabolizing enzymes in the efficacy of tamoxifen treatment of breast cancer is subject to substantial interest and controversy. CYP2D6 have been intensively studied, but the role of CYP2C19 is less elucidated, and we studied the association of CYPC19 genotype and recurrence of breast cancer. We used outcome and genotyping data from the large publicly available International Tamoxifen Pharmacogenomics Consortium (ITPC) dataset. Cox regression was used to compute the hazard ratios (HRs) for recurrence. CYP2C19 genotype data was available for 2 423 patients and the final sample cohort comprised 2 102 patients. CYP2C19*2 or *19 alleles did not influence DFS. For the CYP2C19*2 allele, the HR was 1.05 (CI 0.78–1.42) and 0.79 (CI 0.32–1.94) for hetero- and homozygote carriers, respectively. The corresponding HR for hetero- and homozygote carriers of the CYP2C19*17 allele were 1.02 (CI 0.71–1.46) and 0.57 (CI 0.26–1.24), respectively. Accounting for CYP2D6 genotype status did not change these estimates. We found no evidence to support a clinically meaningful role of CYP2C19 polymorphisms and response to tamoxifen in breast cancer patients and, consequently, CYP2C19 genotype status should not be included in clinical decisions on tamoxifen treatment.

Catalpol promotes cellular apoptosis in human HCT116 colorectal cancer cells via microRNA-200 and the downregulation of PI3K-Akt signaling pathway

Catalpol is an effective active ingredient that functions as a diuretic and laxative, and exhibits blood sugar-lowering, liver protective, anti-aging and anticancer effects. In traditional Chinese medicine, catalpol is believed to be Yin nourishing. The anticancer effect of catalpol on human HCT116 colorectal cancer cells were investigated and the mechanism of action was evaluated. Cellular viability was detected using an MTT assay. Caspase-3 and caspase-9 activity, cellular apoptosis and nucleic morphology were analyzed using caspase-3 and caspase-9 activity assay kits, flow cytometric assays and DAPI staining assay, respectively. Western blot analysis was used to measure the protein expressions of phosphatidylinositol 3-kinase (PI3K), phosphorylated-protein kinase B (p-Akt) and Akt. Expression of microRNA-200 was detected using the reverse transcription-quantitative polymerase chain reaction. HCT116 cells were incubated with PI3K inhibitors in order to analyze the effect of catalpol on cell proliferation. Catalpol was able to inhibit HCT116 cell proliferation. Furthermore, catalpol induced apoptosis in HCT116 cells, which depended on the increased activities of caspase-3 and -9. In addition, catalpol reduced the expression of PI3K, p-Akt and Akt in HCT116 cells. However, downregulation of PI3K/Akt decreased the viability of HCT116 cells following treatment with catalpol and enhanced microRNA-200 expression. Catalpol promoted cellular apoptosis in human HCT116 colorectal cancer cells through upregulation of microRNA-200 expression, which depended on a downregulation of the phosphatase and tensin homolog/PI3K-Akt signaling pathway.

Effects of CYP2D6 and CYP3A5 polymorphisms on tamoxifen and its metabolites in Thai breast cancer patients

Purpose

This study aimed to determine the effects of CYP2D6 and CYP3A5 polymorphisms on the levels of tamoxifen (TAM) and its metabolites in the plasma of breast cancer patients. The protocol was designed to test the associations between CYP2D6, CYP3A5 genotypes and phenotypes (extensive metabolizer [EM], intermediate metabolizer [IM] and poor metabolizer [PM]) and TAM, N-desmethyl tamoxifen (NDMT), endoxifen (END) and 4-hydroxytamoxifen (4OHT) concentrations.

Patients and methods

One hundred and thirty-four Thai breast cancer patients from the Thai Tamoxifen Project undergoing TAM treatment who met the inclusion/exclusion criteria were recruited. Plasma samples were assessed for the concentrations of TAM and its metabolites using high-performance liquid chromatography. The data are presented as actual values and metabolic ratios (MR). The hypotheses were tested using Kruskal–Wallis or Mann–Whitney U test, including the simple main effects analysis.

Results

The patients had stage 0–IV breast cancer. The mean age and body mass index were 51.6±11.6 years and 24.0±4.3, respectively. Also, 53.0% of them were premenopausal, 10.4% were perimenopausal and 36.6% were postmenopausal, while 23.1% were CYP2D6-EM/CYP3A5-EM and 20.9% carried only CYP2D6 and CYP3A5 incomplete alleles. The median concentrations of TAM, NDMT, END and 4OHT were 374.7 (interquartile range [IQR] 230.2) ng/mL, 1,064.9 (IQR 599.6) ng/mL, 54.5 (IQR 52.5) ng/mL and 5.0 (IQR 3.1) ng/mL, respectively. MR (TAM-NDMT) and MR (NDMT-END) were statistically different (p=0.013 and p=0.014, respectively), while MR (4OHT-END) was not statistically different within the CYP2D6 phenotype (p=0.594). MR (TAM-4OHT) was not statistically different within the CYP2D6 phenotype (p=0.079), but it was potentially different from CYP3A5-PM (p=0.056). None of the MR was statistically different within the CYP3A5 phenotype.

Conclusion

CYP2D6 polymorphisms appear to affect END concentration through an NDMT subpathway and potentially affect 4OHT concentrations through a 4OHT subpathway in CYP3A5-PM group.

Cytochrome P-450 2D6 (CYP2D6) Genotype and Breast Cancer Recurrence in Tamoxifen-Treated Patients: Evaluating the Importance of Loss of Heterozygosity

Tamoxifen therapy for estrogen receptor-positive breast cancer reduces the risk of recurrence by approximately one-half. Cytochrome P-450 2D6, encoded by the polymorphic cytochrome P-450 2D6 gene (CYP2D6), oxidizes tamoxifen to its most active metabolites. Steady-state concentrations of endoxifen (4-hydroxy-N-desmethyltamoxifen), the most potent antiestrogenic metabolite, are reduced in women whose CYP2D6 genotypes confer poor enzyme function. Thirty-one studies of the association of CYP2D6 genotype with breast cancer survival have yielded heterogeneous results. Some influential studies genotyped DNA from tumor-infiltrated tissues, and their results may have been susceptible to germline genotype misclassification from loss of heterozygosity at the CYP2D6 locus. We systematically reviewed 6 studies of concordance between genotypes obtained from paired nonneoplastic and breast tumor-infiltrated tissues, all of which showed excellent CYP2D6 genotype agreement. We applied these concordance data to a quantitative bias analysis of the subset of the 31 studies that were based on genotypes from tumor-infiltrated tissue to examine whether genotyping errors substantially biased estimates of association. The bias analysis showed negligible bias by discordant genotypes. Summary estimates of association, with or without bias adjustment, indicated no clinically important association between CYP2D6 genotype and breast cancer survival in tamoxifen-treated women.

CYP2D6 polymorphisms and their influence on risperidone treatment

Cytochrome P450 enzyme especially CYP2D6 plays a major role in biotransformation. The interindividual variations of treatment response and toxicity are influenced by the polymorphisms of this enzyme. This review emphasizes the effect of CYP2D6 polymorphisms in risperidone treatment in terms of basic knowledge, pharmacogenetics, effectiveness, adverse events, and clinical practice. Although the previous studies showed different results, the effective responses in risperidone treatment depend on the CYP2D6 polymorphisms. Several studies suggested that CYP2D6 polymorphisms were associated with plasma concentration of risperidone, 9-hydroxyrisperidone, and active moiety but did not impact on clinical outcomes. In addition, CYP2D6 poor metabolizer showed more serious adverse events such as weight gain and prolactin than other predicted phenotype groups. The knowledge of pharmacogenomics of CYP2D6 in risperidone treatment is increasing, and it can be used for the development of personalized medication in term of genetic-based dose recommendation. Moreover, the effects of many factors in risperidone treatment are still being investigated. Both the CYP2D6 genotyping and therapeutic drug monitoring are the important steps to complement the genetic-based risperidone treatment.

Association of CYP2D6*10 (c.100C>T) polymorphisms with clinical outcome of breast cancer after tamoxifen adjuvant endocrine therapy in Chinese population

Tamoxifen is the most widely used adjuvant endocrine therapy for breast cancer. However, the pharmacogenetic effect of CYP2D6 on its efficacy remains unclear. Therefore, this study aimed to evaluate the association of CYP2D6*10 (c.100C>T) polymorphisms with clinical outcome in Chinese breast cancer patients. A total of 72 tamoxifen-treated early breast cancer patients were included in this study. CYP2D6*10 (c.100C>T) polymorphisms (C/C: wild type; T/T: homozygous mutant genotype T; C/T: heterozygote genotype C) were detected by pyrosequencing. The plasma concentrations of tamoxifen and its two major active metabolites were determined by liquid chromatography tandem mass spectrometry (LC-MS). Disease-free survival (DFS) and overall survival (OS) were assessed by Kaplan-Meier analysis, while the Cox proportional hazards model was used in multivariate tests for prognostic significance. We found that T/T carrier showed the lowest serum concentration of endoxifen as compared to C/C and C/T carriers (p<0.01). In the subgroup of patients below 40 years of age, T/T carriers appeared to have the shortest DFS and OS as compared to other genotype carriers (p<0.01). When genotypes (C/C, C/T and T/T carriers) and other clinical characteristics were adjusted, tumor size (>2 cm) and grades were independent prognostic factors for DFS but not OS (tumor size >2 cm: HR: 3.870, 95% CI: 1.045-14.330, P = 0.043; tumor grades: HR: 2.230, 95% CI: 1.090-4.562, P = 0.028). In conclusion, the T/T genotype is a negative prognostic factor in young breast cancer patients using tamoxifen. Tumor size (>2 cm) and grades are independent prognostic factors for DFS, when genotype of CYP2D6*10 (c.100C>T) is adjusted.

Prevalence of CYP2D6*2, CYP2D6*4, CYP2D6*10, and CYP3A5*3 in Thai breast cancer patients undergoing tamoxifen treatment

Background

Tamoxifen (TAM) is used in breast cancer treatment, but interindividual variabilities in TAM-metabolizing enzymes exist and have been linked to single nucleotide polymorphisms in the respective encoding genes. The different alleles and genotypes of these genes have been presented for Caucasians and Asians. This study aimed to explore the prevalence of the incomplete functional alleles and genotypes of the CYP2D6 and CYP3A5 genes in Thai breast cancer patients undergoing TAM treatment.

Patients and methods

In total, 134 Thai breast cancer patients were randomly invited to join the Thai Tamoxifen Project. Their blood samples were collected and extracted for individual DNA. The alleles and genotypes were determined by real-time polymerase chain reaction with TaqMan^® Drug Metabolism Genotyping Assays.

Results

The patients were aged from 27.0 years to 82.0 years with a body mass index range from 15.4 to 40.0, with the majority (103/134) in the early stage (stages 0–II) of breast cancer. The median duration of TAM administration was 17.2 months (interquartile range 16.1 months). Most (53%) of the patients were premenopausal with an estrogen receptor (ER) and progesterone receptor (PR) status of ER+/PR+ (71.7%), ER+/PR− (26.9%), ER−/PR+ (0.7%), and ER−/PR− (0.7%). The allele frequencies of CYP2D6*1, CYP2D6*2, CYP2D6*4, CYP2D6*10, CYP3A5*1, and CYP3A5*3 were 72.9%, 3.2%, 1.1%, 22.8%, 37.3%, and 62.7%, respectively, while the genotype frequencies of CYP2D6*1/*1, CYP2D6*1/*2, CYP2D6*2/*2, CYP2D6*4/*4, CYP2D6*1/*10, CYP2D6*2/*10, CYP2D6*4/*10, CYP2D6*10/*10, CYP3A5*1/*1, CYP3A5*1/*3, and CYP3A5*3/*3 were 9.7%, 2.2%, 3.7%, 1.5%, 15.7%, 9.7%, 3.7%, 53.7%, 13.4%, 47.8%, and 38.8%, respectively.

Conclusion

The majority (97.8%) of Thai breast cancer patients undergoing TAM treatment carry at least one incomplete functional allele, including 20.9% of the patients who carry only incomplete functional alleles for both the CYP2D6 and CYP3A5 genes. This research indicates the high prevalence of these defective alleles that are involved in TAM-metabolic pathways that might further affect TAM treatment.

Effects of Pharmacogenetics on the Pharmacokinetics and Pharmacodynamics of Tamoxifen

The antiestrogenic drug tamoxifen is widely used in the treatment of estrogen receptor-α-positive breast cancer and substantially decreases recurrence and mortality rates. However, high interindividual variability in response is observed, calling for a personalized approach to tamoxifen treatment. Tamoxifen is bioactivated by cytochrome P450 (CYP) enzymes such as CYP2B6, CYP2C9, CYP2C19, CYP2D6 and CYP3A4/5, resulting in the formation of active metabolites, including 4-hydroxy-tamoxifen and endoxifen. Therefore, polymorphisms in the genes encoding these enzymes are proposed to influence tamoxifen and active tamoxifen metabolites in the serum and consequently affect patient response rates. To tailor tamoxifen treatment, multiple studies have been performed to clarify the influence of polymorphisms on its pharmacokinetics and pharmacodynamics. Nevertheless, personalized treatment of tamoxifen based on genotyping has not yet met consensus. This article critically reviews the published data on the effect of various genetic polymorphisms on the pharmacokinetics and pharmacodynamics of tamoxifen, and reviews the clinical implications of its findings. For each CYP enzyme, the influence of polymorphisms on pharmacokinetic and pharmacodynamic outcome measures is described throughout this review. No clear effects on pharmacokinetics and pharmacodynamics were seen for various polymorphisms in the CYP encoding genes CYP2B6, CYP2C9, CYP2C19 and CYP3A4/5. For CYP2D6, there was a clear gene-exposure effect that was able to partially explain the interindividual variability in plasma concentrations of the pharmacologically most active metabolite endoxifen; however, a clear exposure-response effect remained controversial. These controversial findings and the partial contribution of genotype in explaining interindividual variability in plasma concentrations of, in particular, endoxifen, imply that tailored tamoxifen treatment may not be fully realized through pharmacogenetics of metabolizing enzymes alone.

Clinically relevant genetic variants of drug-metabolizing enzyme and transporter genes detected in Thai children and adolescents with autism spectrum disorder

Single-nucleotide polymorphisms (SNPs) among drug-metabolizing enzymes and transporters (DMETs) influence the pharmacokinetic profile of drugs and exhibit intra- and interethnic variations in drug response in terms of efficacy and safety profile. The main objective of this study was to assess the frequency of allelic variants of drug absorption, distribution, metabolism, and elimination-related genes in Thai children and adolescents with autism spectrum disorder. Blood samples were drawn from 119 patients, and DNA was extracted. Genotyping was performed using the DMET Plus microarray platform. The allele frequencies of the DMET markers were generated using the DMET Console software. Thereafter, the genetic variations of significant DMET genes were assessed. The frequencies of SNPs across the genes coding for DMETs were determined. After filtering the SNPs, 489 of the 1,931 SNPs passed quality control. Many clinically relevant SNPs, including CYP2C19*2, CYP2D6*10, CYP3A5*3, and SLCO1B1*5, were found to have frequencies similar to those in the Chinese population. These data are important for further research to investigate the interpatient variability in pharmacokinetics and pharmacodynamics of drugs in clinical practice.

Association of CYP2D6*10, OATP1B1 A388G, and OATP1B1 T521C polymorphisms and overall survival of breast cancer patients after tamoxifen therapy

Background

The global incidence of breast cancer is increasing, mainly due to the sharp rise in breast cancer incidence in Asia. The aim of this study was to evaluate the association of CYP2D6*10 (c.100C>T and c.1039C>T), OATP1B1 A388G, and OATP1B1 T521C polymorphisms with overall survival (OS) for hormone receptor (estrogen receptor or progesterone receptor)-positive tumors (ER+/PR+) breast cancer patients after adjuvant tamoxifen (TAM) therapy.

Material/Method

We included 296 invasive breast cancer patients with hormone receptor-positive tumors during the period 2002–2009. We collected patient data, including clinical features, TAM therapy, and survival status. Archived paraffin blocks from surgery were the source of tissue for genotyping. CYP2D6*10, OATP1B1 A388G, and T521C polymorphisms were detected by direct sequencing of genomic DNA. OS was assessed with Kaplan-Meier analysis, while the Cox proportional hazards model was used to implement multivariate tests for the prognostic significance.

Results

There was a significant difference in OS between OATP1B1 T521C wild-type and the mutant genotype C carrier (P=0.034). However, there was no difference in overall survival between wild-type and carrier groups for CYP2D6*10 (P=0.096) and OATP1B1 A388G (P=0.388), respectively.

Conclusions

These results suggest that the OATP1B1 T521C mutation may be an independent prognostic marker for breast cancer patients using TAM therapy.

Association of CYP3A4/5, ABCB1 and ABCC2 polymorphisms and clinical outcomes of Thai breast cancer patients treated with tamoxifen

Background

Pharmacogenetic study of cytochrome P450 (CYP) gene CYP2D6 and tamoxifen outcomes remain controversial. Apart from CYP2D6, other drug-metabolizing enzymes and transporters also play a role in tamoxifen metabolic pathways. The aim of this study is to investigate the impact of CYP3A4/5, ABCB1, and ABCC2 polymorphisms on the risk of recurrence in Thai patients who received tamoxifen adjuvant therapy.

Methods

Patients with early-stage breast cancer who received tamoxifen adjuvant therapy were recruited in this study. All six single-nucleotide polymorphisms (SNPs), including CYP3A4*1B (−392 A>G)/*18(878 T>C), CYP3A5*3(6986 G>A), ABCB1 3435 C>T, ABCC2*1C(−24 C>T), and ABCC2 68231 A>G, were genotyped using real-time polymerase chain reaction assays. The impacts of genetic variants on disease-free survival (DFS) were analyzed using the Kaplan–Meier method and Cox regression analysis.

Results

The ABCB1 3435 C>T was found to have the highest allele frequency among other variants; however, CYP3A4*1B/*18 could not be found in this study. Patients with heterozygous ABCB1 3435 CT genotype showed significantly shorter DFS than those with homozygous 3435 CC genotype (P = 0.041). In contrast, patients who carried homozygous 3435 TT genotype showed no difference in DFS from wild-type 3435 CC patients. Cox regression analysis showed that the relative risk of recurrence was increased by five times (P = 0.043; hazard ratio = 5.11; 95% confidence interval: 1.05–24.74) in those patients carrying ABCB1 3435 CT genotype compared to those with ABCB1 3435 CC.

Conclusion

ABCB1 3435 C>T is likely to have a clinically significant impact on recurrence risk in Thai patients with breast cancer who receive tamoxifen adjuvant therapy.