Publications by authors named "Tahar van der Straaten"

49 Publications

Effects of age and genetic variations in VKORC1, CYP2C9 and CYP3A4 on the phenprocoumon dose in pediatric patients.

Pharmacogenomics 2018 10 12;19(15):1195-1202. Epub 2018 Sep 12.

Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands.

Aim: To study the effects of clinical and genetic factors on the phenprocoumon dose requirement in pediatric patients and to develop a dosing algorithm.

Methods: Pediatric patients who used phenprocoumon were invited to participate in a retrospective follow-up study. Clinical information and genotypes of genetic variations in CYP2C9, VKORC1, CYP4F2, CYP2C18 and CYP3A4 were collected and tested with linear regression for association with phenprocoumon dose requirement.

Results: Of the 41 patients included in the analysis, age, VKORC1, CYP2C9*2/*3 and CYP3A4*1B were statistically significantly associated with dose requirement, and together explained 80.4% of the variability in phenprocoumon dose requirement.

Conclusion: Our study reveals that age and genetic variations explain a significant part of the variability in phenprocoumon dose requirement in pediatric patients.
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http://dx.doi.org/10.2217/pgs-2018-0095DOI Listing
October 2018

Genetic polymorphisms in angiogenesis-related genes are associated with worse progression-free survival of patients with advanced gastrointestinal stromal tumours treated with imatinib.

Eur J Cancer 2017 11 18;86:226-232. Epub 2017 Oct 18.

Department of Medical Oncology, Leiden University Medical Center, Leiden, The Netherlands.

Background: Imatinib 400 mg per day is first-line therapy for patients with gastrointestinal stromal tumours (GISTs). Although clinical benefit is high, progression-free survival (PFS) is variable. This study explores the relationship of single nucleotide polymorphisms (SNPs) in genes related to imatinib pharmacokinetics and pharmacodynamics and PFS in imatinib-treated patients with advanced GIST.

Methods: In 227 patients a pharmacogenetic pathway analysis was performed. Genotype data from 36 SNPs in 18 genes were tested in univariate analyses to investigate their relationship with PFS. Genetic variables which showed a trend (p < 0.1) were tested in a multivariate model, in which each singular SNP was added to clinicopathological factors.

Results: In univariate analyses, PFS was associated with synchronous metastases (p = 0.0008) and the mutational status (p = 0.004). Associations with rs1870377 in KDR (additive model, p = 0.0009), rs1570360 in VEGFA (additive model, p = 0.053) and rs4149117 in SLCO1B3 (mutant dominant model, 0.027) were also found. In the multivariate model, significant associations and trends with shorter PFS were found for synchronous metastases (HR 1.94, p = 0.002), KIT exon 9 mutation (HR 2.45, p = 0.002) and the SNPs rs1870377 (AA genotype, HR 2.61, p = 0.015), rs1570360 (AA genotype, HR 2.02, p = 0.037) and rs4149117 (T allele, HR 0.62, p = 0.083).

Conclusion: In addition to KIT exon 9 mutation and synchronous metastases, SNPs in KDR, VEGFA and SLCO1B3 appear to be associated with PFS in patients with advanced GIST receiving 400-mg imatinib. If validated, specific SNPs may serve as predictive biomarkers to identify patients with an increased risk for progressive disease during imatinib therapy.
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http://dx.doi.org/10.1016/j.ejca.2017.09.025DOI Listing
November 2017

Single-nucleotide polymorphisms in the genes of CES2, CDA and enzymatic activity of CDA for prediction of the efficacy of capecitabine-containing chemotherapy in patients with metastatic breast cancer.

Pharmacol Res 2018 02 18;128:122-129. Epub 2017 Aug 18.

Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands. Electronic address:

We examined whether genetic polymorphisms (SNPs) in the capecitabine activation pathway and CDA enzymatic activity were associated with prognosis, benefit from capecitabine-containing treatment or capecitabine-related toxicities. The study population comprised 188 metastatic breast cancer patients of the ATX trial (EudraCT 2006-006058-83) randomized for first-line paclitaxel and bevacizumab with (ATX) or without capecitabine (AT). Cumulative capecitabine dose until grade ≥2 hand-foot syndrome or until first dose reduction were toxicity endpoints. We genotyped CDA c.-451C>T (rs532545), CDA c.-33delC (rs3215400) and CES2 c.-806C>G (rs11075646). CDA activity in baseline serum was measured with a spectrophotometric assay and values were analyzed using a median cut-off or as continuous variable. CDA c.-33delC was prognostic for overall survival (OS) independent of hormone receptor status. For the predictive analysis, progression-free survival benefit from ATX over AT was observed in patients with a CDA c.-33del/del or del/insC genotype, a CDA c.-451CC or CT genotype, and a CES2 c.-806CC genotype compared with their counterparts. There was a higher response rate for ATX over AT in patients with a CDA c.-451CT or TT genotype. Patients with high CDA enzymatic activity had more benefit from capecitabine, while this was marginally observed in the CDA low group. Toxicity endpoints were not associated with any candidate markers. In conclusion, CDA c.-33delC was associated with OS. Since particular SNPs in CDA and CES2 were associated with benefit from the addition of capecitabine to AT, their predictive value should be explored in a higher number of patients.
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http://dx.doi.org/10.1016/j.phrs.2017.08.005DOI Listing
February 2018

Flexible and Scalable Full-Length CYP2D6 Long Amplicon PacBio Sequencing.

Hum Mutat 2017 03 18;38(3):310-316. Epub 2017 Jan 18.

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, Leiden, 2333ZA, The Netherlands.

Cytochrome P450 2D6 (CYP2D6) is among the most important genes involved in drug metabolism. Specific variants are associated with changes in the enzyme's amount and activity. Multiple technologies exist to determine these variants, like the AmpliChip CYP450 test, Taqman qPCR, or Second-Generation Sequencing, however, sequence homology between cytochrome P450 genes and pseudogene CYP2D7 impairs reliable CYP2D6 genotyping, and variant phasing cannot accurately be determined using these assays. To circumvent this, we sequenced CYP2D6 using the Pacific Biosciences RSII and obtained high-quality, full-length, phased CYP2D6 sequences, enabling accurate variant calling and haplotyping of the entire gene-locus including exonic, intronic, and upstream and downstream regions. Unphased diplotypes (Roche AmpliChip CYP450 test) were confirmed for 24 of the 25 samples, including gene duplications. Cases with gene deletions required additional specific assays to resolve. In total, 61 unique variants were detected, including variants that had not previously been associated with specific haplotypes. To further aid genomic analysis using standard reference sequences, we have established an LOVD-powered CYP2D6 gene-variant database, and added all reference haplotypes and data reported here. We conclude that our CYP2D6 genotyping approach produces reliable CYP2D6 diplotypes and reveals information about additional variants, including phasing and copy-number variation.
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http://dx.doi.org/10.1002/humu.23166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5324676PMC
March 2017

ERCC2/XPD Lys751Gln alter DNA repair efficiency of platinum-induced DNA damage through P53 pathway.

Chem Biol Interact 2017 Feb 24;263:55-65. Epub 2016 Dec 24.

Dept. of Toxicology, School of Public Health, China Medical University, Shenyang, PR China. Electronic address:

Platinum-based treatment causes Pt-DNA adducts which lead to cell death. The platinum-induced DNA damage is recognized and repaired by the nucleotide excision repair (NER) system of which ERCC2/XPD is a critical enzyme. Single nucleotide polymorphisms in ERCC2/XPD have been found to be associated with platinum resistance. The aim of the present study was to investigate whether ERCC2/XPD Lys751Gln (rs13181) polymorphism is causally related to DNA repair capacity of platinum-induced DNA damage. First, cDNA clones expressing different genotypes of the polymorphism was transfected to an ERCC2/XPD defective CHO cell line (UV5). Second, all cells were treated with cisplatin. Cellular survival rate were investigated by MTT growth inhibition assay, DNA damage levels were investigated by comet assay and RAD51 staining. The distribution of cell cycle and the change of apoptosis rates were detected by a flow cytometric method (FCM). Finally, P53mRNA and phospho-P53 protein levels were further investigated in order to explore a possible explanation. As expected, there was a significantly increased in viability of UV5 as compared to UV5 after cisplatin treatment. The DNA damage level of UV5 was significant decreased compared to UV5 at 24 h of treatment. Mutation of ERCC2rs13181 AA to CC causes a prolonged S phase in cell cycle. UV5 alleviated the apoptosis compared to UV5, meanwhile P53mRNA levels in UV was also lower when compared UV5. It co-incides with a prolonged high expression of phospho-P53, which is relevant for cell cycle regulation, apoptosis, and the DNA damage response (DDR). We concluded that ERCC2/XPD rs13181 polymorphism is possibly related to the DNA repair capacity of platinum-induced DNA damage. This functional study provides some clues to clarify the relationship between cisplatin resistance and ERCC2/XPDrs13181 polymorphism.
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http://dx.doi.org/10.1016/j.cbi.2016.12.015DOI Listing
February 2017

Genetic polymorphisms in 19q13.3 genes associated with alteration of repair capacity to BPDE-DNA adducts in primary cultured lymphocytes.

Mutat Res Genet Toxicol Environ Mutagen 2016 Dec 29;812:39-47. Epub 2016 Oct 29.

Dept. of Toxicology, School of Public Health, China Medical University, Shenyang, PR China. Electronic address:

Benzo[a]pyrene(B[a]P), and its ultimate metabolite Benzo[a]pyrene 7,8-diol 9,10-epoxide (BPDE), are classic DNA damaging carcinogens. DNA damage in cells caused by BPDE is normally repaired by Nucleotide Excision Repair (NER) and Base Excision Repair (BER). Genetic variations in NER and BER can change individual DNA repair capacity to DNA damage induced by BPDE. In the present study we determined the number of in vitro induced BPDE-DNA adducts in lymphocytes, to reflect individual susceptibility to Polycyclic aromatic hydrocarbons (PAHs)-induced carcinogenesis. The BPDE-DNA adduct level in lymphocytes were assessed by high performance liquid chromatography (HPLC) in 281 randomly selected participants. We genotyped for 9 single nucleotide polymorphisms (SNPs) in genes involved in NER (XPB rs4150441, XPC rs2228001, rs2279017 and XPF rs4781560), BER (XRCC1 rs25487, rs25489 and rs1799782) and genes located on chromosome 19q13.2-3 (PPP1R13L rs1005165 and CAST rs967591). We found that 3 polymorphisms in chromosome 19q13.2-3 were associated with lower levels of BPDE-DNA adducts (MinorT allele in XRCC1 rs1799782, minor T allele in PPP1R13L rs1005165 and minor A allele in CAST rs967571). In addition, a modified comet assay was performed to further confirm the above conclusions. We found both minor T allele in PPP1R13L rs1005165 and minor A allele in CAST rs967571 were associated with the lower levels of BPDE-adducts. Our data suggested that the variant genotypes of genes in chromosome 19q13.2-3 are associated with the alteration of repair efficiency to DNA damage caused by Benzo[a]pyrene, and may contribute to enhance predictive value for individual's DNA repair capacity in response to environmental carcinogens.
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http://dx.doi.org/10.1016/j.mrgentox.2016.10.004DOI Listing
December 2016

Genotypes of CYP2C8 and FGD4 and their association with peripheral neuropathy or early dose reduction in paclitaxel-treated breast cancer patients.

Br J Cancer 2016 Nov 13;115(11):1335-1342. Epub 2016 Oct 13.

Department of Medical Oncology, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.

Background: The purpose of this study was to evaluate single-nucleotide polymorphisms (SNPs) in genes encoding key metabolising enzymes or involved in pharmacodynamics for possible associations with paclitaxel-induced peripheral neuropathy.

Methods: The study population consists of 188 women from the multicenter, randomised, phase II ATX trial (BOOG2006-06; EudraCT number 2006-006058-83) that received paclitaxel and bevacizumab without or with capecitabine as first-line palliative therapy of HER2-negative metastatic breast cancer. Genotyping of CYP2C8*3 (c.416G>A), CYP3A4*22 (c.522-191C>T), TUBB2A (c.-101T>C), FGD4 (c.2044-236G>A) and EPHA5 (c.2895G>A) was performed by real-time PCR. Toxicity endpoints were cumulative dose (1) until first onset of grade ⩾1 peripheral neuropathy and (2) until first paclitaxel dose reduction from related toxicity (NCI-CTCAE version 3.0). SNPs were evaluated using the Kaplan-Meier method, the Gehan-Breslow-Wilcoxon test and the multivariate Cox regression analysis.

Results: The rate of grade ⩾1 peripheral neuropathy was 67% (n=126). The rate of dose reduction was 46% (n=87). Age ⩾65 years was a risk factor for peripheral neuropathy (HR=1.87, P<0.008), but not for dose reduction. When adjusted for age, body surface area and total cumulative paclitaxel dose, CYP2C8*3 carriers had an increased risk of peripheral neuropathy (HR=1.59, P=0.045). FGD4 c.2044-236 A-allele carriers had an increased risk of paclitaxel dose reduction (HR per A-allele=1.38, P=0.036) when adjusted for total cumulative paclitaxel dose.

Conclusions: These findings may point towards clinically useful indicators of early toxicity, but warrant further investigation.
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http://dx.doi.org/10.1038/bjc.2016.326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5129817PMC
November 2016

Exploring genetic and non-genetic risk factors for delayed graft function, acute and subclinical rejection in renal transplant recipients.

Br J Clin Pharmacol 2016 07 10;82(1):227-37. Epub 2016 May 10.

Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands.

Aims: This study aimed at identifying pharmacological factors such as pharmacogenetics and drug exposure as new predictive biomarkers for delayed graft function (DGF), acute rejection (AR) and/or subclinical rejection (SCR).

Methods: Adult renal transplant recipients (n = 361) on cyclosporine-based immunosuppression were followed for the first 6 months after transplantation. The incidence of DGF and AR were documented as well as the prevalence of SCR at 6 months in surveillance biopsies. Demographic, transplant-related factors, pharmacological and pharmacogenetic factors (ABCB1, CYP3A5, CYP3A4, CYP2C8, NR1I2, PPP3CA and PPP3CB) were analysed in a combined approach in relation to the occurrence of DGF, AR and prevalence of SCR at month 6 using a proportional odds model and time to event model.

Results: Fourteen per cent of the patients experienced at least one clinical rejection episode and only DGF showed a significant effect on the time to AR. The incidence of DGF correlated with a deceased donor kidney transplant (27% vs. 0.6% of living donors). Pharmacogenetic factors were not associated with risk for DGF, AR or SCR. A deceased donor kidney and acute rejection history were the most important determinants for SCR, resulting in a 52% risk of SCR at 6 months (vs. 11% average). In a sub-analysis of the patients with AR, those treated with rejection treatment including ATG, significantly less frequent SCR was found in the 6-month biopsy (13% vs. 50%).

Conclusions: Transplant-related factors remain the most important determinants of DGF, AR and SCR. Furthermore, rejection treatment with depleting antibodies effectively prevented SCR in 6-month surveillance biopsies.
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http://dx.doi.org/10.1111/bcp.12946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4917801PMC
July 2016

The ERCC2/XPD Lys751Gln polymorphism affects DNA repair of benzo[a]pyrene induced damage, tested in an in vitro model.

Toxicol In Vitro 2016 Aug 29;34:300-308. Epub 2016 Apr 29.

Dept. Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden, The Netherlands.

Nucleotide excision repair (NER) is an important defense mechanism of the body to exogenous carcinogens and mutagens, such as benzo[a]pyrene (B[a]P). Genetic polymorphisms in ERCC2/XPD, a critical element in NER, are thought to be associated with individual's cancer susceptibility. Although ERCC2/XPD Lys751Gln (rs13181) is the most studied polymorphism, the impact of this polymorphism on DNA repair capacity to carcinogen remains unclear. In the present study, cDNA clones carrying different genotypes of ERCC2/XPD (Lys751Gln) were introduced into an ERCC2/XPD deficient cell line (UV5) in a well-controlled biological system. After B[a]P treatment, cell growth inhibition rates and DNA damage levels in all cells were detected respectively. As expected, we found that the DNA repair capacity in UV5 cells was restored to levels similar to wildtype parent AA8 cells upon introduction of the cDNA clone of ERCC2/XPD (Lys751). Interestingly, after B[a]P treatment, transfected cells expressing variant ERCC2/XPD (751Gln) showed an enhanced cellular sensitivity and a diminished DNA repair capacity. The wildtype genotype AA (Lys) was found to be associated with a higher DNA repair capacity as compared to its polymorphic genotype CC (Gln). These data indicate that ERCC2/XPD Lys751Gln polymorphism affects DNA repair capacity after exposure to environmental carcinogens such as B[a]P in this well-controlled in vitro system and could act as a biomarker to increase the predictive value to develop cancer.
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http://dx.doi.org/10.1016/j.tiv.2016.04.015DOI Listing
August 2016

Insulin-like growth factor 1 receptor expression and IGF1R 3129G > T polymorphism are associated with response to neoadjuvant chemotherapy in breast cancer patients: results from the NEOZOTAC trial (BOOG 2010-01).

Breast Cancer Res 2016 Jan 6;18(1). Epub 2016 Jan 6.

Department of Medical Oncology, Leiden University Medical Center, Albinusdreef 2, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.

Background: The insulin-like growth factor 1 (IGF-1) pathway is involved in cell growth and proliferation and is associated with tumorigenesis and therapy resistance. This study aims to elucidate whether variation in the IGF-1 pathway is predictive for pathologic response in early HER2 negative breast cancer (BC) patients, taking part in the phase III NEOZOTAC trial, randomizing between 6 cycles of neoadjuvant TAC chemotherapy with or without zoledronic acid.

Methods: Formalin-fixed paraffin-embedded tissue samples of pre-chemotherapy biopsies and operation specimens were collected for analysis of IGF-1 receptor (IGF-1R) expression (n = 216) and for analysis of 8 candidate single nucleotide polymorphisms (SNPs) in genes of the IGF-1 pathway (n = 184) using OpenArray® RealTime PCR. Associations with patient and tumor characteristics and chemotherapy response according to Miller and Payne pathologic response were performed using chi-square and regression analysis.

Results: During chemotherapy, a significant number of tumors (47.2 %) showed a decrease in IGF-1R expression, while in a small number of tumors an upregulation was seen (15.1 %). IGF-1R expression before treatment was not associated with pathological response, however, absence of IGF-1R expression after treatment was associated with a better response in multivariate analysis (P = 0.006) and patients with a decrease in expression during treatment showed a better response to chemotherapy as well (P = 0.020). Moreover, the variant T allele of 3129G > T in IGF1R (rs2016347) was associated with a better pathological response in multivariate analysis (P = 0.032).

Conclusions: Absent or diminished expression of IGF-1R after neoadjuvant chemotherapy was associated with a better pathological response. Additionally, we found a SNP (rs2016347) in IGF1R as a potential predictive marker for chemotherapy efficacy in BC patients treated with TAC.

Trial Registration: ClinicalTrials.gov NCT01099436 . Registered April 6, 2010.
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http://dx.doi.org/10.1186/s13058-015-0663-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4702399PMC
January 2016

Genome Wide Association Study for Predictors of Progression Free Survival in Patients on Capecitabine, Oxaliplatin, Bevacizumab and Cetuximab in First-Line Therapy of Metastatic Colorectal Cancer.

PLoS One 2015 29;10(7):e0131091. Epub 2015 Jul 29.

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, The Netherlands; PO box 9600, 2300 RC Leiden, The Netherlands.

Purpose: Despite expanding options for systemic treatment, survival for metastatic colorectal cancer (mCRC) remains limited and individual response is difficult to predict. In search of pre-treatment predictors, pharmacogenetic research has mainly used a candidate gene approach. Genome wide association (GWA) studies offer the benefit of simultaneously analyzing a large number of SNPs, in both known and still unidentified functional regions. Using a GWA approach, we searched for genetic markers affecting progression free survival (PFS) in mCRC patients treated with first-line capecitabine, oxaliplatin and bevacizumab (CAPOX-B), with or without cetuximab.

Patients And Methods: 755 patients were included in the CAIRO2-trial, a multicenter phase III trial, randomizing between first-line treatment with CAPOX-B versus CAPOX-B plus cetuximab. Germline DNA and complete clinical information was available from 553 patients and genome wide genotyping was performed, using Illumina's OmniExpress beadchip arrays, with 647,550 markers passing all quality checks. Another 2,202,473 markers were imputated by using HapMap2. Association with PFS was analysed using a Cox proportional hazards model.

Results: One marker, rs885036, associated significantly with PFS (P = 2.17x10(-8)) showing opposite effects on PFS depending on treatment arm. The minor allele was associated with increased PFS in patients receiving cetuximab. A cluster of markers located on chromosome 8 associated with PFS, irrespective of treatment arm (P-values of 2.30x10(-7) to 1.04x10(-6)).

Conclusion: This is the first GWA study to find SNPs affecting PFS in mCRC patients treated with CAPOX-B, either with or without cetuximab. Rs885036 is a potential predictive marker for cetuximab efficacy. These markers need to be validated in independent treatment cohorts.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131091PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4519298PMC
April 2016

A misleading false-negative result using Neisseria gonorrhoeae opa MGB multiplex PCR assay in patient's rectal sample due to partial mutations of the opa gene.

New Microbiol 2015 Jul 6;38(3):431-4. Epub 2015 Jul 6.

Medical Microbiology Laboratory, Atal-Medial Medical Diagnostic Center, Jan Tooropstraat, Amsterdam, Netherlands.

A 53-year-old homosexual man presented at his general practitioner (GP) practice with a suspicion of sexually transmitted infection. Initial NAAT screening was performed for Chlamydia trachomatis and Neisseria gonorrhoeae. The patient was positive for Neisseria gonorrhoeae both for his urine and rectal sample. The subsequent confirmation test for Neisseria gonorrhoeae by a second laboratory was only confirmed for the urine sample and the rectal sample was negative. We report a case of a potential false-negative diagnosis of Neisseria gonorrhoeae due to mutations of DNA sequence in the probe region of opa-MGB assay of the rectal sample. The patient did not suffer any discomfort as diagnosis of Neisseria gonorrhoeae in his urine sample had already led to treatment by prescribing the patient with Ceftriaxone 500 mg IV dissolved in 1 ml lidocaine 2% and 4 mL saline. The patient also received a prescription for Azithromycin (2x500 mg).
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July 2015

GenoChip CYP2D6 macroarray as a method to genotype for CYP2D6 variants: results of a validation study in a Caucasian population.

Pharmacogenomics 2015 1;16(7):681-7. Epub 2015 May 1.

Aim: The aim of this study was to investigate the concordance between the novel GenoChip CYP2D6 macroarray and the AmpliChip, which is considered the gold standard in CYP2D6 genotyping.

Materials & Methods: Germline DNA of 200 patients was genotyped with both the AmpliChip and the GenoChip CYP2D6 macroarray.

Results: One hundred and ninety-eight samples (99%) showed concordance. In two discordant samples the AmpliChip identified a *41 allele while the GenoChip CYP2D6 macroarray did not. Sanger sequencing showed that the 2988G>A mutation and thus the *41 allele was not present in both samples.

Conclusion: We conclude that that the GenoChip CYP2D6 macroarray is a valid method for detecting genetic variants of CYP2D6 in a Caucasian population. Original submitted 10 November 2014; Revision submitted 23 February 2015.
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http://dx.doi.org/10.2217/pgs.15.30DOI Listing
March 2016

FcGR genetic polymorphisms and the response to adalimumab in patients with rheumatoid arthritis.

Pharmacogenomics 2015 ;16(4):373-81

Department of Clinical Pharmacy, San Cecilio University Hospital, Instituto de Investigación Biosanitaria ibs. Granada, Granada, Spain.

Aim: The aim of our study was to explore the potential of FcGR genetic polymorphisms as a predictor of adalimumab efficacy in rheumatoid arthritis (RA) patients.

Materials & Methods: The study population was composed of 302 Dutch RA patients receiving adalimumab therapy. The FcGR2A (R131>H; rs1801274) and FcGR3A (F158>V; rs396991) genetic variants were genotyped using the TaqMan(®) allelic discrimination technology. Treatment outcome was evaluated with the use of the 28-joint disease activity score criteria (DAS28) and good response and remission were classified according to European League Against Rheumatism (EULAR) criteria.

Results: Comparing allelic frequencies between responders and nonresponders, the presence of the FcGR2A*R allele was associated with EULAR good response at 14 weeks (p = 0.017, odds ratio: 1.53, 95% CI: 1.08-2.17). No significant association was found for FcGR3A, with good response or remission. The combined effect of both FcGR2A and FcGR3A SNPs showed a trend for association with EULAR good response (p-value = 0.041, odds ratio: 1.38, 95% CI: 1.01-1.89).

Conclusion: Our results indicate that FcGR polymorphisms could be a determinant of adalimumab efficacy in RA patients. Original submitted 28 July 2014; Revision submitted 19 December 2014.
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http://dx.doi.org/10.2217/pgs.14.178DOI Listing
January 2016

High-quality genotyping data from formalin-fixed, paraffin-embedded tissue on the drug metabolizing enzymes and transporters plus array.

J Mol Diagn 2015 Jan;17(1):4-9

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, Leiden, the Netherlands.

The Affymetrix Drug Metabolizing Enzymes and Transporters (DMET) Plus array covers 1936 markers in 231 genes involved in drug metabolism and transport. Blood- and saliva-derived DNA works well on the DMET array, but the utility of DNA from FFPE tissue has not been reported for this array. As the ability to use DNA from FFPE tissue on the array could open the potential for large retrospective sample collections, we examined the performance and reliability of FFPE-derived DNA on the DMET Plus array. Germline DNA isolated from archived normal FFPE tissue blocks stored for 3 to 19 years and matched blood or saliva from 16 patients with osteosarcoma were genotyped on the DMET Plus array. Concordance was assessed by calculating agreement and the κ-statistic. We observed high call rates for both the blood- or saliva-derived DNA samples (99.4%) and the FFPE-derived DNA samples (98.9%). Moreover, the concordance among the 16 blood- or saliva-derived DNA and FFPE DNA pairs was high (97.4%, κ = 0.915). This is the first study showing that DNA from normal FFPE tissue provides accurate and reliable genotypes on the DMET Plus array compared with blood- or saliva-derived DNA. This finding provides an opportunity for pharmacogenetic studies in diseases with high mortality rates and prevents a bias in studies where otherwise only alive patients can be included.
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http://dx.doi.org/10.1016/j.jmoldx.2014.08.003DOI Listing
January 2015

Germline variants in the CYP19A1 gene are related to specific adverse events in aromatase inhibitor users: a substudy of Dutch patients in the TEAM trial.

Breast Cancer Res Treat 2014 Apr 4;144(3):599-606. Epub 2014 Mar 4.

Department of Surgery, Leiden University Medical Center, Leiden, The Netherlands.

Musculoskeletal adverse events (MSAEs) and vasomotor symptoms (VMSs) are known side-effects of aromatase inhibitors, and may be related to genetic variations of the aromatase gene (CYP19A1). We investigated the relationship between these specific AEs and single nucleotide polymorphisms (SNPs) in the CYP19A1 gene in postmenopausal, hormone receptor-positive early breast cancer (BC) patients treated with adjuvant exemestane for 5 years. Dutch patients who were randomized to receive 5 years of exemestane in the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial were included. A tagging-SNP approach was performed, covering 80 % of variations of the CYP19A1 gene with 30 SNPs. Logistic regression analyses were used to assess the risk of reporting VMSs or MSAEs in relation to genotypes within selected SNPs. Of 737 included patients, 281 patients reported at least one MSAE (n = 210) or VMS (n = 163). Homozygous AA genotype of rs934635 was associated with a significantly higher odds of MSAEs (multivariate odds ratio (OR) 4.66, p = 0.008) and VMSs (multivariate OR 2.78, p = 0.044). Regarding both rs1694189 and rs7176005, the homozygous variant genotypes (TT) were associated with a higher odds of VMSs, but not MSAEs (OR 1.758, p = 0.025 and OR 6.361, p = 0.021, respectively). Our exploratory analysis demonstrated that some CYP19A1 gene variations may be associated with MSAEs and/or VMSs. Specifically, patients with the homozygous variant rs934635 genotype reported more MSAEs and VMSs. Although further confirmatory studies are warranted, genomic profiling can help identify patients at an increased risk of reporting these specific AEs, potentiating further personalized BC treatment.
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http://dx.doi.org/10.1007/s10549-014-2873-2DOI Listing
April 2014

Concordance of genotype for polymorphisms in DNA isolated from peripheral blood and colorectal cancer tumor samples.

Pharmacogenomics 2013 Dec;14(16):2005-12

Department of Clinical Oncology (K-1-P), Leiden University Medical Center, PO Box 9600, 2300 RC, Leiden, The Netherlands.

Background & Aim: Results from different pharmacogenetic association studies in colorectal cancer are often conflicting. Both peripheral blood and formalin-fixed, paraffin-embedded (FFPE) tissue are routinely used as DNA source. This could cause bias due to somatic alterations in tumor tissue, such as loss of heterozygosity. We therefore compared genotypes in DNA from peripheral blood and FFPE colorectal tumor samples for SNPs with putative influence on the cytotoxicity of chemotherapy.

Materials & Methods: Eleven SNPs in nine genes involved in anticancer drug metabolism or efficacy were determined in matched samples from blood and FFPE tissue of colorectal tumors by pyrosequencing and TaqMan(®) techniques. The κ-statistic was calculated to assess concordance.

Results: A total of 149 paired FFPE tissue and EDTA blood DNA samples were available for comparison. Overall, 20 out of 1418 genotypes were discordant (1.4%); in ten cases, loss of heterozygosity could not be ruled out. Only GSTP1 showed significant discordance between FFPE tissue and blood genotype (κ = 0.947; 95% CI: 0.896-0.998).

Conclusion: FFPE tissue-derived DNA can be used as a valid proxy for germline DNA for a selection of SNPs in (retrospective) pharmacogenetic association studies in colorectal cancer. However, for future studies, genotyping of blood-derived DNA is preferred.
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http://dx.doi.org/10.2217/pgs.13.169DOI Listing
December 2013

CYP2D6 genotype in relation to hot flashes as tamoxifen side effect in a Dutch cohort of the tamoxifen exemestane adjuvant multinational (TEAM) trial.

Breast Cancer Res Treat 2014 Jan 22;143(1):171-9. Epub 2013 Nov 22.

Department of Clinical Oncology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.

In tamoxifen-treated breast cancer patients the occurrence of hot flashes may be associated with effective estrogen receptor antagonism dependent on genetic variations of metabolic enzymes and the estrogen receptor. Early breast cancer patients who were randomized to receive tamoxifen, followed by exemestane within the tamoxifen exemestane adjuvant multinational trial were genotyped for five CYP2D6 alleles. CYP2D6 genotypes and phenotypes were related to the occurrence of hot flashes as adverse event during the first year of tamoxifen use (primary aim) and the time to the occurrence of hot flashes as AE during the complete time on tamoxifen (secondary aim). In addition, exploratory analyses on 22 genetic variants of other metabolic enzymes and two common polymorphisms in the estrogen receptor-1 were performed. No association was found between the CYP2D6 genotype/phenotype or any other genetic variant and hot flashes during the first year. Only higher age was related to a lower incidence of hot flashes in the first year (adjusted odds ratio 0.94, 95 % CI 0.92-0.96; p < 0.001). The ESR1 PvuII XbaI CG haplotype was associated with the time to the occurrence of hot flashes during the complete time on tamoxifen (CG/CG vs. CG/other + other/other: adjusted hazard ratio 0.49, 95 % CI 0.25-0.97; p = 0.04). In conclusion, the CYP2D6 genotypes and phenotypes were not associated with the occurrence of hot flashes. Common polymorphisms in the estrogen receptor-1 might predict hot flashes as common tamoxifen side effect, although this finding needs replication.
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http://dx.doi.org/10.1007/s10549-013-2777-6DOI Listing
January 2014

Excision Repair Cross-Complementation group 1 (ERCC1) C118T SNP does not affect cellular response to oxaliplatin.

Mutat Res 2014 Jan 9;759:37-44. Epub 2013 Nov 9.

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands. Electronic address:

Aims: ERCC1 is involved in the repair of oxaliplatin-induced DNA damage. Studies for the association of the C118T SNP with clinical response to treatment with platinum drugs have rendered inconsistent results. We investigated the ERCC1 C118T SNP with respect to overall and progression-free survival in patients with advanced colorectal cancer (ACC) treated with oxaliplatin and in vitro DNA repair capacity after oxaliplatin exposure. In addition we discuss discrepancies from other studies concerning ERCC1 C118T.

Materials And Methods: Progression-free survival was determined in 145 ACC patients treated with oxaliplatin-based chemotherapy in a phase 3 trial. For the in vitro studies regarding ERCC1 functionality, we transfected an ERCC1 negative cell line with 118C or 118T ERCC1. Cellular sensitivity and DNA repair capacity after exposure to oxaliplatin was examined by Sulphorodamine B growth inhibition assay, COMET assay and Rad51 foci staining.

Results: We found no association between ERCC1 C118T and progression-free or overall survival. In addition, transfection of either 118C or 118T restores DNA-repair capacity of UV20 cells to the same level and chemosensitivity to oxaliplatin was similar in ERCC1 118C and 118T transfected cells.

Conclusion: This study shows that the ERCC1 C118T variants are not associated with survival in ACC patients treated with oxaliplatin or the in vitro sensitivity and DNA-repair capacity in 118C and 118T transfected cell lines. Therefore, ERCC1 C118T genotyping seems of no value in individualizing oxaliplatin based chemotherapy in ACC.
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http://dx.doi.org/10.1016/j.mrfmmm.2013.11.001DOI Listing
January 2014

Exploratory analysis of 1936 SNPs in ADME genes for association with busulfan clearance in adult hematopoietic stem cell recipients.

Pharmacogenet Genomics 2013 Dec;23(12):675-83

Departments of aClinical Pharmacy and Toxicology bMedical Statistics and Bioinformatics cHematology, Leiden University Medical Center, Leiden, The Netherlands.

Background: Busulfan is used in preparative regimens before stem cell transplantation. There is significant interpatient variability in busulfan pharmacokinetics (PK) and exposure is related to outcome. Polymorphisms in genes encoding glutathione-S-transferases have been associated with busulfan PK but only explain a limited portion of the observed variability.

Aim: The aim of this study is to identify additional genetic variants associated with busulfan PK by interrogating 1936 variants in 225 genes involved in drug absorption, distribution, metabolism, and excretion (ADME).

Materials And Methods: In an exploratory cohort (n=65), patients who received busulfan were genotyped with the DMET array. Top SNPs and haplotypes associated with busulfan clearance were validated in an independent validation cohort (n=78).

Results: In the exploratory cohort, seven variants were identified to be associated with busulfan clearance (P<0.001). In the validation cohort, only GSTA5 (rs4715354 and rs7746993) remained significantly associated with busulfan clearance (P=0.025).

Conclusion: This is the first study using an exploratory pharmacogenetic approach to explain the interindividual variability in busulfan PK. The role of glutathione-S-transferases was confirmed, but no additional genetic markers involved in drug ADME appear to be associated with busulfan PK.
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http://dx.doi.org/10.1097/FPC.0000000000000007DOI Listing
December 2013

Effect of genetic variants GSTA1 and CYP39A1 and age on busulfan clearance in pediatric patients undergoing hematopoietic stem cell transplantation.

Pharmacogenomics 2013 Nov;14(14):1683-90

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.

Background: Busulfan is used in preparative regimens prior to stem cell transplantation in pediatric patients. There is significant interpatient variability in busulfan pharmacokinetics (PK) and exposure is related to outcome. To date, only polymorphisms in genes encoding for glutathione-S-transferases were studied, but could only explain a small portion of the variability in PK.

Aim: To investigate the effect of seven genetic markers on busulfan clearance and the effect of ontogenesis on these genetic variants in a pediatric population.

Materials & Methods: In an earlier study of our group seven genetic markers in GSTA1, CYP2C19, CYP39A1, ABCB4, SLC22A4 and SLC7A8 were associated with busulfan clearance in adult patients. Eighty four pediatric patients were genotyped for these markers and genotype was associated with busulfan clearance.

Results & Conclusion: GSTA1 and CYP39A1 were found to be associated with busulfan clearance. When combined, the two haplotypes explained 17% of the variability in busulfan clearance. Furthermore, the effect of GSTA1 haplotype on clearance was dependent on age.
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http://dx.doi.org/10.2217/pgs.13.159DOI Listing
November 2013

A novel specific pyrosequencing method for genotyping FCGR3A rs396991 without coamplification of homologous gene FCGR3B.

Pharmacogenet Genomics 2013 Nov;23(11):631-5

Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden, The Netherlands.

Monoclonal antibodies, such as rituximab, trastuzumab, and cetuximab, mediate immune response by binding to Fcγ receptors. The frequently occurring Phe158Val variant of the FCGR3A gene has increased binding affinity and consequently may affect immune response. Several pharmacogenetic association studies have genotyped this variant (FCGR3A rs396991), but with disconcordant results. In addition, in some of these studies genotype distribution was not in Hardy-Weinberg equilibrium, and samples were excluded from analysis because of genotype inconsistency. Genotyping problems of FCGR3A rs396991 are most likely due to sequence homology with the FCGR3B gene. For that reason, we developed a novel pyrosequencing method specifically for genotyping FCGR3A rs396991 and confirmed that the FCGR3B gene is not coamplified.
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http://dx.doi.org/10.1097/FPC.0b013e328365a4f2DOI Listing
November 2013

Plasmid derived external quality controls for genetic testing.

Methods Mol Biol 2013 ;1015:189-97

Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden, The Netherlands.

Since the human genome has been fully sequenced, and presence of single nucleotide polymorphisms (SNPs) appeared abundant, many studies are associating SNPs with clinical response or even with disease. For some diseases or drug treatments these associations are clear, so that genetic screening for such SNPs or mutations is a standard procedure. For that reason, many different techniques have been developed for fast and easy screening for such specific SNPs/mutations. For reliable screening, the use of controls with known genotypes is indispensable. Plasmids are an ideal tool for making controls which can serve as an inexhaustible source, making new validation superfluous.In this chapter we describe how plasmid controls can be made using DNA with a heterozygous genotype, and also from DNA of which only one allele is available.
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http://dx.doi.org/10.1007/978-1-62703-435-7_12DOI Listing
February 2014

ERCC1 and ERCC2 haplotype modulates induced BPDE-DNA adducts in primary cultured lymphocytes.

PLoS One 2013 4;8(4):e60006. Epub 2013 Apr 4.

Department of Toxicology, School of Public Health, China Medical University, Shenyang, People's Republic of China.

Background: Benzo[a]pyrene(B[a]P), and its ultimate metabolite Benzo[a]pyrene 7,8-diol 9,10-epoxide (BPDE), are classic DNA damaging carcinogens. DNA damage caused by BPDE is normally repaired by Nucleotide Excision Repair (NER), of which ERCC1 and ERCC2/XPD exert an indispensable role. Genetic variations in ERCC1 and ERCC2 have been related to DNA repair efficiency. In this study we used lymphocytes from healthy individuals to show that polymorphisms in ERCC1 and ERCC2 are directly associated with decreased DNA repair efficiency.

Methods: ERCC1 (rs3212986 and rs11615) and ERCC2 (rs13181, rs1799793 and rs238406) were genotyped in 818 healthy Han individuals from the northeast of China. BPDE induced DNA adducts in lymphocytes were assessed by high performance liquid chromatography (HPLC) in 282 randomly selected participants. The effect of ERCC1 rs3212986 and ERCC2 rs238406 on DNA damage caused by B[a]P was assessed with a modified comet assay.

Results: We found that the variant genotypes of ERCC1 rs3212986 and ERCC2 rs238406 were associated with the high levels of BPDE-DNA adducts. Especially ERCC1 rs3212986 A-allele variant was significantly associated with the high BPDE-DNA adducts. Haplotype analysis showed that the ERCC1 haplotype AC (OR = 2.36, 95% CI = 1.84-2.97), ERCC2 haplotype AGA (OR = 1.51, 95% CI = 1.06-2.15) and haplotype block AGAAC (OR = 5.28, 95% CI = 2.95-9.43), AGCAC (OR = 1.35 95% CI = 1.13-1.60) were linked with high BPDE-DNA adducts. In addition, we found that the combined minor alleles of ERCC1 rs3212986 and ERCC2 rs238406 were associated with a reduced DNA repair capacity.

Conclusions: Our results suggest that the variant genotypes of ERCC1 rs3212986 and ERCC2 rs238406 are associated with decreased repair efficiency of BPDE induced DNA damage, and may be predictive for an individual's DNA repair capacity in response to environmental carcinogens.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0060006PLOS
November 2013

Excision repair of BPDE-adducts in human lymphocytes: diminished capacity associated with ERCC1 C8092A (rs3212986) polymorphism.

Arch Toxicol 2013 Apr 1;87(4):699-709. Epub 2012 Dec 1.

Department of Toxicology, School of Public Health, China Medical University, 92#, North 2 Road, Heping District, Shenyang 110001, Liaoning Province, People's Republic of China.

Benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), a metabolite of Benzo[a]pyrene (B[a]P), is a high-risk factor for development of a number of cancers. DNA damage caused by BPDE is normally repaired by Nucleotide Excision Repair system of which ERCC1 exerts an important role. We investigated whether two single nucleotide polymorphisms in ERCC1 (C19007T; rs11615 and C8092A; rs3213986) affected the repair efficacy of BPDE-DNA adducts. We collected peripheral blood of 780 healthy individuals from the northeast of China and detected the genotypes of rs11615 and rs3213986. The amount of induced BPDE-DNA adducts in lymphocytes from 117 randomly selected participants was assessed by HPLC. Presence of BPDE-DNA adducts in nucleus of lymphocytes was visualized using the modified comet assay. ERCC1 and CAST (3' adjacent gene of ERCC1) mRNA expression levels were quantified after in vitro exposure to BPDE. We found that the minor A allele in rs3212986 was related to higher levels of BPDE-DNA adducts and holistic marking DNA damage (P < 0.01). Haplotype CA (rs11615 and rs3213986) was also associated with an elevated risk of high BPDE-DNA adduct levels (OR = 1.801, 95 % CI of OR 1.191-2.724). Interestingly, in participants with AA genotype for rs3213986, CAST mRNA level was decreased compared to individuals with the homozygous CC genotype. Our findings suggests that ERCC1 C8092A (rs3213986) is associated with a diminished capacity of repairing BPDE-DNA adducts and may be used as a valid biomarker to predict an individual's risk to develop cancer upon exposure to environmental carcinogens.
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http://dx.doi.org/10.1007/s00204-012-0986-0DOI Listing
April 2013

Population pharmacokinetics and pharmacogenetics of everolimus in renal transplant patients.

Clin Pharmacokinet 2012 Jul;51(7):467-80

Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, the Netherlands.

Background And Objective: Everolimus is a novel macrolide immunosuppressant used in the prevention of acute and chronic rejection of solid organ transplants. Everolimus is being actively investigated worldwide as a non-nephrotoxic alternative for calcineurin inhibitors. Its highly variable pharmacokinetics and narrow therapeutic window make it difficult to maintain an adequate exposure to prevent serious adverse effects. The primary objective of this study was to improve prediction of everolimus systemic exposure in renal transplant patients by describing the pharmacokinetics of everolimus and identifying the influence of demographic factors and a selection of polymorphisms in genes coding for ABCB1, CYP3A5, CYP2C8 and PXR. The secondary objective of this study was to develop a limited sampling strategy to enable prediction of everolimus exposure in an efficient way and to compare it with the widely used trough blood concentration (C(trough)) monitoring.

Methods: A total of 783 blood samples were obtained from 53 renal transplant patients who had been switched from a triple therapy of ciclosporin, mycophenolate mofetil and prednisolone to a calcineurin inhibitor-free dual therapy of everolimus (twice daily) and prednisolone. Everolimus blood concentrations were analysed in whole blood using liquid chromatography-tandem mass spectrometry during routine therapeutic drug monitoring targeting an area under the blood concentration-time curve from time zero to 12 hours (AUC(12)) of 120 μg · h/L. A population pharmacokinetic model was developed and demographic factors and genetic polymorphisms in genes coding for ABCB1, CYP3A5, CYP2C8 and PXR were included as covariates. In addition, a limited sampling strategy was developed.

Results: Maintaining everolimus systemic exposure at an AUC(12) of 120 μg · h/L resulted in low rejection rates but considerable numbers of adverse events and toxicity. Everolimus pharmacokinetics were best described by a two-compartment model with lag-time (oral clearance = 17.9 L/h; volume of distribution of the central compartment after oral administration [V(1)/F] = 148 L and first-order absorption rate constant [k(a)] = 7.36 h-1). Ideal body weight was significantly related to V(1)/F. None of the selected polymorphisms in genes coding for enzymes involved in distribution and metabolism of everolimus had a significant influence on everolimus pharmacokinetics. The pharmacokinetic limited sampling model (C(trough) and whole blood drug concentration at 2 hours postdose [C(2)]) resulted in a significantly improved prediction of everolimus exposure compared with the widely used C(trough) monitoring.

Conclusion: A two-compartment pharmacokinetic model with lag-time describing the concentration-time profile of oral everolimus in renal transplant patients has been developed using pharmacokinetic modelling. Ideal body weight significantly influenced V(1)/F of everolimus; however, the selected polymorphisms in genes coding for ABCB1, CYP3A5, CYP2C8 and PXR had no clinically relevant effect on everolimus pharmacokinetics. Everolimus C(trough) and C(2) as a limited sampling model can be used to accurately estimate everolimus systemic exposure, an improvement over the widely used C(trough) monitoring.
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http://dx.doi.org/10.2165/11599710-000000000-00000DOI Listing
July 2012

ERCC1 and XPD/ERCC2 polymorphisms' predictive value of oxaliplatin-based chemotherapies in advanced colorectal cancer has an ethnic discrepancy: a meta-analysis.

J Clin Lab Anal 2012 Jan;26(1):10-5

Department of Hygiene Toxicology, China Medical University, Shenyang, People's Republic of China.

Our purpose is to evaluate the predictive value of the genetic polymorphisms of Excision repair cross-complementing group 1 (ERCC1) and xeroderma pigmentosum group D/excision repair cross-complementing group 2 (XPD/ERCC2) in patients with advanced colorectal cancer receiving oxaliplatin-based chemotherapy, and we performed a meta-analysis in order to obtain a more precise estimation for a more optimizing individual chemotherapy. The relevant cohort studies were identified by searching the electronic databases of MEDLINE, EMBASE, and CNKI. We used ''colorectal,'' ''cancer,'' ''carcinoma,'' ''ERCC1,'' ''XPD or ERCC2,'' ''polymorphism,'' ''oxaliplatin,'' ''treatment,'' or ''chemotherapy'' as key words. Inclusion criteria were patients with advanced colorectal cancer receiving oxaliplatin-based chemotherapy, evaluation of polymorphism of ERCC1 and XPD/ ERCC2, and overall response rate (ORR). In this meta-analysis, a total of seven studies were selected according to the inclusion criteria. Five studies investigated ERCC1 codon 118 polymorphisms and three studies evaluated XPD/ERCC2 codon 751 polymorphisms. For ERCC1 codon C118T polymorphism, the ORR to oxaliplatin-based chemotherapy in patients with C/C wild genotype was 77.27% and it was 69.30% for C/T and T/T variant genotype. The pooled odds ratio (OR) for C/C wild-type vs. C/T and T/T genotype was 1.11 (95% CI, 0.86-1.42; P = 0.42). For XPD/ERCC2 Lys751Gln polymorphism, the response rate was 86.58 and 67.57% in patients with the A/A and either one or two C alleles (A/C or C/C) respectively, and the pooled OR was 1.15 (95% CI, 1.01-1.30; P = 0.03). Furthermore, we chose subgroup analysis in order to find the difference between the Caucasian and Asian ethnicity. The results indicated that Oxaliplatin sensitivity was significantly associated with ERCC1 C118T polymorphism in Asian people. XPD/ERCC2 Lys751Gln polymorphism had the predictive value especially for the patients from the America and Europe.
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http://dx.doi.org/10.1002/jcla.20494DOI Listing
January 2012

Alternative methods to a TaqMan assay to detect a tri-allelic single nucleotide polymorphism rs757210 in the HNF1β gene.

Clin Chem Lab Med 2011 Oct 21;50(2):279-84. Epub 2011 Oct 21.

Department of Clinical Pharmacy and Toxicology, Leiden, University Medical Center, Leiden, The Netherlands.

Background: Several studies report difficulties in genotyping HNF1β rs757210 using TaqMan probes. This is possibly due to the tri-allelic nature of this single nucleotide polymorphism (SNP). The aim of the present research was to develop alternative methods for genotyping rs757210.

Methods: Pyrosequencing and high resolution melting analysis of small amplicons (HRM) were developed and tested in panels of type 2 diabetes mellitus patients (n=258) and healthy blood donors (n=183). Results were confirmed by Sanger sequencing.

Results: With pyrosequencing, allele frequencies for the A, G and C allele of 0.42, 0.56, 0.02 and 0.37, 0.62, 0.01 were established in the panel of type 2 diabetes mellitus patients and healthy blood donors, respectively. Similar results were found using the more routinely available HRM method. Results for pyrosequencing and HRM were in 99.6% concordance.

Conclusions: Pyrosequencing and HRM can be used to genotype the tri-allelic SNP rs757210 in the HNF1β gene and have the advantage over the commercially available TaqMan analysis that they can determine the rare C-allele variant.
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http://dx.doi.org/10.1515/CCLM.2011.758DOI Listing
October 2011

Activation of tumor-promoting type 2 macrophages by EGFR-targeting antibody cetuximab.

Clin Cancer Res 2011 Sep 25;17(17):5668-73. Epub 2011 Jul 25.

Department of Clinical Pharmacy & Toxicology, Leiden University Medical Center, Leiden, The Netherlands.

Purpose: In a recent randomized phase III clinical trial in metastatic colorectal cancer patients, the addition of the anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) cetuximab to bevacizumab and chemotherapy resulted in decreased progression-free survival, in particular for patients with the high-affinity FcγRIIIA.

Experimental Design: The presence of natural killer (NK) cells and type 2 (M2) macrophages in colorectal cancer was determined by immunohistochemistry, using antibodies to lineage-specific markers NKp46 and CD68 with CD163, respectively. Influence of tumor-bound cetuximab on M2 macrophages was carried out in vitro with EGFR-expressing tumor cells and short-term differentiated monocytes from blood donors, who were typed for the FcγRIIIA polymorphism (CD16).

Results: Antibody-dependent cellular cytotoxicity by NK cells is generally proposed as one of the antitumor mechanisms of mAbs. We found that CD163-positive M2 macrophages are much more abundant in colorectal carcinomas. In vitro analysis of M2 macrophages revealed high levels of Fc-gamma receptors (FcγR) and PD-L1 and production of IL-10 and VEGF but not IL-12. These anti-inflammatory and tumor-promoting mediators were released upon coculture with EGFR-positive tumor cells loaded with low concentrations of cetuximab. Macrophage activation depended on EGFR expression on the tumor cells, FcγRs, target specificity of the mAb and mobility of antibody complexes. Cetuximab-induced macrophage responses were more pronounced for FCGR3A 158-Val (high-affinity) carriers.

Conclusion: These results suggest that tumor-promoting M2 macrophages are activated by the therapeutic mAb cetuximab in the local tumor microenvironment and argue that this immune mechanism should be taken into account for the application of therapeutic antibodies.
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http://dx.doi.org/10.1158/1078-0432.CCR-11-0239DOI Listing
September 2011
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