ABCG2 Polymorphisms Research Articles

Genetic analysis of ABCG2 and SLC2A9 gene polymorphisms in gouty arthritis in a Korean population.

Background/Aims:Gout is a common inf lammatory arthritis triggered by the crystallization of uric acid in the joints. Serum uric acid levels are highly heritable, suggesting a strong genetic component. Independent studies to confirm the genetic associations with gout in various ethnic populations are warranted. We investigated the association of polymorphisms in the ABCG2 and SLC2A9 genes with gout in Korean patients and healthy individuals.Methods:We consecutively enrolled 109 patients with gout and 102 healthy controls. The diagnosis of gout was based on the preliminary criteria of the America College of Rheumatology. Genomic DNA was extracted from whole blood samples. We identified single nucleotide polymorphism (SNP) changes in the ABCG2 and SLC2A9 genes using a direct sequencing technique. rs2231142 in ABCG2 and rs6449213 and rs16890979 in SLC2A9 and nearby regions were amplified by polymerase chain reaction.Results:Patients with gout had significantly higher A/A genotype (29.3% vs. 4.9%, respectively) and A allele (52.8% vs. 26.5%, respectively) frequencies of rs2231142 in ABCG2 than did controls (χ2 = 29.42, p < 0.001; odds ratio, 3.32; 95% confidence interval, 2.11 to 5.20). We found novel polymorphisms (c.881A>G and c.1002+78G>A) in the SLC2A9 gene. The univariate logistic regression analysis revealed that the c.881A>G and c.1002+78G>A SNPs were significantly higher in patients than in controls.Conclusions:We demonstrated a significant association between rs2231142 in the ABCG2 gene and gout and identified novel SNPs, c.881A>G and c.1002+78G>A, in the SLC2A9 gene that may be associated with gout in a Korean population.

Quantitative Analysis of the ABCG2 c.421C > A Polymorphism Effect on In Vivo Transport Activity of Breast Cancer Resistance Protein (BCRP) Using an Intestinal Absorption Model

ABCG2 c.421C>A is one of the most frequent polymorphisms in ABCG2, which encodes the breast cancer resistance protein (BCRP). Clinical pharmacogenetic studies have shown that the plasma area under the concentration-time curve (AUC) values after oral administration of BCRP substrate drugs are significantly higher in subjects homozygous for the c.421C>A polymorphism (421AA) than in wild-type subjects (421CC). The aim of this study was to quantitatively estimate the in vivo decrease of BCRP function caused by the c.421C>A polymorphism based on clinical pharmacokinetic data. Assuming that the pharmacokinetic alteration is accounted for by intestinal BCRP, the ratio of the transport activity of the mutated BCRP to that of the wild-type was optimized by comparing calculations from an intestinal absorption model and clinical pharmacokinetic data. In conclusion, the in vivo intestinal BCRP transport activity in 421AA subjects is estimated to be approximately 23% of that in the 421CC subjects.

Association of ABCB1 and FLT3 Polymorphisms with Toxicities and Survival in Asian Patients Receiving Sunitinib for Renal Cell Carcinoma.

Sunitinib is a tyrosine kinase inhibitor used as first-line treatment for metastatic renal cell carcinoma (mRCC). Asian ethnicity has been previously associated with lower clearance and greater toxicities for sunitinib treatment, relative to Caucasian ethnicity. Research focusing on identifying corresponding biomarkers of efficacy and toxicity has been hitherto conducted in Caucasian populations, and few of the reported associations have been externally validated. Our work thus aims to investigate candidate biomarkers in Asian patients receiving sunitinib, comparing the observed genotype effects with those reported in Caucasian populations. Using data from 97 Asian mRCC patients treated with sunitinib, we correlated 7 polymorphisms in FLT3, ABCB1, VEGFR2, ABCG2 and BIM with patient toxicities, response, and survival. We observed a stronger association of FLT3 738T genotype with leucopenia in our Asian dataset than that previously reported in Caucasian mRCC patients (odds ratio [OR]=8.0; P=0.03). We observed significant associations of FLT3 738T (OR=2.7), ABCB1 1236T (OR=0.3), ABCB1 3435T (OR=0.1), ABCB1 2677T (OR=0.4), ABCG2 421A (OR=0.3) alleles and ABCB1 3435, 1236, 2677 TTT haplotype (OR=0.1) on neutropenia. Primary resistance (OR=0.1, P=0.004) and inferior survival (progression-free: hazard ratio [HR]=5.5, P=0.001; overall: HR=5.0, P=0.005) were associated with the ABCB1 3435, 1236, 2677 TTT haplotype. In conclusion, ABCB1 and FLT3 polymorphisms may be helpful in predicting sunitinib toxicities, response and survival benefit in Asian mRCC patients. We have also validated the association between FLT3 738T and sunitinib-induced leucopenia previously reported in Caucasian populations, but have not validated other reported genetic associations.

Polymorphisms in ATP-binding cassette transporter genes and interaction with diet and life style factors in relation to colorectal cancer in a Danish prospective case-cohort study

Background and aims. The ATP-binding cassette (ABC) transporter family transports various molecules across the enterocytes in the gut protecting the intestine against potentially harmful substances. Moreover, ABC transporters are involved in mucosal immune defence through interaction with cytokines. The study aimed to assess whether polymorphisms in ABCB1, ABCC2 and ABCG2 were associated with risk of colorectal cancer (CRC) and to investigate gene–environment (dietary factors, smoking and use of non-steroidal anti-inflammatory drugs) and gene–gene interactions between previously studied polymorphisms in IL1B and IL10 and ABC transporter genes in relation to CRC risk. Materials and methods. We used a Danish prospective case-cohort study of 1010 CRC cases and 1829 randomly selected participants from the Danish Diet, Cancer and Health cohort. Incidence rate ratios were calculated based on Cox’ proportional hazards model. Results. None of the polymorphisms were associated with CRC, but ABCB1 and ABCG2 haplotypes were associated with risk of CRC. ABCB1/rs1045642 interacted with intake of cereals and fiber (p-Value for interaction (Pint) = 0.001 and 0.01, respectively). In a three-way analysis, both ABCB1/rs1045642 and ABCG2/rs2231137 in combination with IL10/rs3024505 interacted with fiber intake in relation to risk of CRC (Pint = 0.0007 and 0.009). Conclusions. Our results suggest that the ABC transporters P-glycoprotein/multidrug resistance 1 and BRCP, in cooperation with IL-10, are involved in the biological mechanism underlying the protective effect of fiber intake in relation to CRC. These results should be replicated in other cohorts to rule out chance findings.

P0172Clinical relevance of a pharmacogenetic approach using multiple transporter genes to predict response and resistance to imatinib therapy in Malaysian patients with chronic myeloid leukaemia

Background Despite success with imatinib mesylate in patients with chronic myeloid leukaemia (CML), emergence of clinical resistance in 30% of patients treated with imatinib mesylate still remains a problem. Resistance could be due to a heterogenous array of mechanisms. Pharamcogenetic variability as a result of genetic polymorphisms in the imatinib mesylate transporter genes ABCB1 , ABCG2 , ABCC1 , and ABCC2 could be potential determinants of variability in imatinib mesylate disposition and efficacy. This study investigated the association between ten polymorphisms of ABCB1 (1236 T>C, 2677G>T/A, 3435C>T), ABCG2 (34G>A, 421 C>A), ABCC1 (2012G>T, 2168G>A), and ABCC2 (−24C>T, 1249G>A, 3972 C>T) genes and response to imatinib mesylate with the ultimate aim of identifying putative genotypes and haplotypes associated with good response or resistance. Methods Blood samples from 215 patients with CML (107 with a good response to imatinib mesylate and 108 who were resistant to imatinib mesylate) were genotyped for the 10 polymorphisms using PCR-RFLP. After determining the genotype and haplotype frequencies, their association with imatinib mesylate response was determined with odds ratio (OR). Findings Resistance was significantly associated with patients who had homozygous ABCB1 1236CC genotype (OR 2.79, p = 0.01). ABCG2 421AA genotype was associated with a good response (OR 0.29, p = 0.01) while 421CC genotype was associated with imatinib mesylate resistance (OR 1.87, p = 0.02). Haplotypes ABCB1 C 1236 G 2677 C 3435 and ABCC2 T- 24 G 1249 T 3972 were associated with imatinib mesylate resistance ( p = 0.04 and p = 0.03 respectively) while ABCG2 A 34 A 421 haplotype was associated with a good response to imatinib mesylate ( p = 0.03). Interpretation Genetic variation in these imatinib mesylate transporter genes might have consequences on mRNA stability, expression, protein folding degradation, intracellular localisation, substrate binding, and/or transporter kinetics and thus modulate variation in response. Pretreatment genotyping of these SNPs in patients with CML could be useful for predicting imatinib mesylate resistance which may allow the best choice of drug treatment for patients with CML.

ABCG2 Gene Polymorphisms as Risk Factors for Atorvastatin Adverse Reactions: A Case–Control Study

To explore the association between dose-related adverse drug reactions (ADRs) of atorvastatin and polymorphisms of ABCG2, taking into account the influence of CYP3A4 and SLCO1B1 genes. Sixty patients who experienced atorvastatin dose-related ADRs and 90 matched patients without ADRs were enrolled in the study. Genotyping for ABCG2 421C > A, CYP3A4*22, SLCO1B1 388A > G, SLCO1B1 521T > C variants was performed by real-time PCR. Patients with ABCG2 421CA or AA genotypes had 2.9 times greater odds of developing atorvastatin dose-dependent ADRs (OR: 2.91; 95% CI: 1.22-6.95; p = 0.016) than those with ABCG2 421CC genotype. After adjustments for clinical and genetic risk factors, ABCG2 remained a statistically significant predictor of adverse drug reactions (OR: 2.75; 95% CI: 1.1-6.87; p = 0.03;). Also, carriers of SLCO1B1 521 TC or CC genotypes had 2.3 greater odds (OR: 1.03-4.98; 95% CI: 1.03-4.98; p = 0.043) of experiencing ADRs caused by atorvastatin in comparison with carriers of SLCO1B1 521 TT genotype. Our study demonstrated an association between atorvastatin-induced ADRs and genetic variants in the ABCG2 gene.

Polymorphisms of ABCG2, ABCB1 and HNF4α are associated with Lamotrigine trough concentrations in epilepsy patients

Lamotrigine (LTG) is commonly used to control seizure in epilepsy patients and with referenced therapeutic windows in clinical practice. This study is to identify and characterize the function of genetic variants that influence the trough concentrations of LTG in epilepsy patients following monotherapy regimen (37.5–250 mg/d). Twelve single nucleotide polymorphisms (SNPs) involved in LTG metabolism and transport pathways, including UGT2B7, ABCB1, ABCG2, NR1I2 and HNF4α were genotyped in 140 Chinese epilepsy patients. Steady-state trough concentration of LTG was measured by a high-performance liquid chromatography method. Polymorphisms in ABCG2 rs2231142, rs3114020, HNF4α rs2071197 and ABCB1 rs1128503 were found to be associated with LTG CDR (concentration/dose normalized by body weight). In addition, multiple linear regression analysis revealed that ABCG2 rs2231142 had a remarkable effect on LTG concentrations which is stated to be 4.8% of the variability of LTG and may also help to interpret ethnic difference in LTG pharmacokinetics. Our findings provided new insights that SNPs of genes involved in the transport of LTG contribute to interpatient variation in LTG pharmacokinetics. Future studies are necessary to determine whether these SNPs can be used to provide LTG dosing guidance and influence seizure control and adverse reaction of LTG.

Impact of ABCG2 and SLCO1B1 polymorphisms on pharmacokinetics of rosuvastatin, atorvastatin and simvastatin acid in Caucasian and Asian subjects: a class effect?

Systemic exposure to rosuvastatin is approximately double that of Caucasians in Asian subjects. We investigated whether this pattern of increased exposure exists for other statins. Plasma exposure following single-dose rosuvastatin 20 mg, atorvastatin 40 mg or simvastatin 40 mg was studied in Chinese, Japanese and Caucasian subjects. Plasma concentrations were determined using LC-MS methods. Impact of polymorphisms in SLCO1B1 (T521>C and A388>G) and in ABCG2 (C421>A) on exposure to rosuvastatin, atorvastatin, simvastatin and simvastatin acid was assessed. Relative to Caucasians, geometric mean area under the curve from time zero to time of last quantifiable concentration was 86 % (90 % confidence interval (CI), 51-130 %) and 55 % (26-91 %) higher for rosuvastatin in Chinese and Japanese subjects, respectively, 53 % (25-88 %) and 69 % (37-108 %) higher for atorvastatin, 23 % (0-52 %) and 12 % (-0.9-39 %) higher for simvastatin and 28 % (5-56 %) and 34 % (10-64 %) higher for simvastatin acid. Geometric mean maximum drug concentration was also proportionally higher for each statin. Polymorphisms in SLCO1B1 T521>C or ABCG2 C421>A were associated with higher exposure to rosuvastatin, atorvastatin and simvastatin acid (but not simvastatin) within a population, but only the ABCG2 C421>A polymorphism contributed towards between-population exposure differences. In individuals carrying wild-type alleles for both SLCO1B1 and ABCG2, area under the plasma concentration-time curve (AUC) still appeared to be higher for rosuvastatin, atorvastatin and simvastatin acid in Chinese and Japanese subjects compared with Caucasians, respectively. Increased exposure to statins in Asian subjects versus Caucasians may represent a more general class phenomenon than previously recognized.

Genetic Variations in ABCG2 Gene Predict Breast Carcinoma Susceptibility and Clinical Outcomes after Treatment with Anthracycline-Based Chemotherapy.

The genetic variants of the ATP-binding cassette, subfamily G, member 2 (ABCG2) are known to be involved in developing cancer risk and interindividual differences in chemotherapeutic response. The polymorphisms in ABCG2 gene were genotyped by using PCR-RFLP assays. We found that ABCG2 G34A GA/AA genotype, C421A AA genotype, and haplotypes 34A-421C and 34G-421A were significantly associated with increased risk for developing breast carcinoma. Furthermore, ABCG2 C421A AA homozygote had a significant enhanced therapeutic response in patients with neoadjuvant anthracycline-based chemotherapy. Moreover, ABCG2 G34A AA genotype carriers displayed a longer OS in ER positive patients or PR positive patients after postoperative anthracycline-based chemotherapy. These results suggested that the ABCG2 polymorphisms might be a candidate pharmacogenomic factor to assess susceptibility and prognosis for breast carcinoma patients.

Population Pharmacokinetics of Daunorubicin in AML: Influence on Clinical Outcome

Daunorubicin (Dnr) has been the choice of anthracycline in the induction chemotherapy of Acute Myeloid Leukemia (AML) along with Cytarabine for the past 4 decades. Drug resistance and relapse of the disease has been the major concern in the success of AML therapy. Several factors, including pharmacokinetics (PK) of Dnr could have impact on treatment outcome as pharmacokinetic effects might limit the amount of drug that reaches the tumor. In this study, we analyzed the factors influencing plasma PK of Daunorubicin and its major metabolite Daunorubicinol (DOL) in AML patients receiving induction chemotherapy and compared PK parameters with clinical outcome (relapse).Sixty four adult denovo AML patients were enrolled in the study after obtaining informed consent. Dnr was given as 1 hour bolus infusion at a dose of 60mg/m2/day for the first 3 days of induction chemotherapy. Peripheral blood were collected at 0, 15min, 1hr, 2hr, 4hr, 6hr and 24hr on the first day of induction chemotherapy. Plasma levels of Dnr and DOL were measured using high performance liquid chromatography coupled with fluorescence detector. Population PK was analyzed by nonlinear mixed effects modeling using Monolix version 4.3.2. Common single nucleotide polymorphisms in ABCB1, ABCG2, CBR1 and CBR3 genes were screened by PCR followed by either sequencing or restriction digestion. In vitro cytotoxicity of the primary AML cells to Dnr was assessed by MTT cell viability assay and IC50 was calculated using ADAPT5 software. The role of plasma Dnr PK on relapse of disease was estimated using nonparametric Mann-Whitney U test.Demographics of the patients enrolled in the study are listed in table 1. PK parameters of Dnr and DOL showed wide inter-individual variation (table2). Older patients had a trend towards lower Dnr clearance (CL) (p=0.09). Patients harboring FLT3-ITD mutations had higher CL than the patients without mutation though not reaching statistical significance. Patients with variants of SNPs rs20572 (exon3) and rs9024 (3’UTR) in CBR1 (which were in complete linkage disequilibrium) had a trend towards significantly higher Dnr AUC [median-0.2711; (0.04903-2.165) vs. median 0.2117; (0.0546-0.9036); p=0.06] than patients with wild-type.Among the 64 patients, complete remission (CR) was documented in 42 (65%) of which, 31% relapsed eventually [median time to relapse 328 (104-864) days]. AML patients who relapsed had significantly lower Dnr AUC [median 0.17 (0.049-2.165) vs. median 0.31 (0.1-1.74); p=0.009] and higher DOL AUC [median 8.67 (1.6-20.1) vs.4.99 (1.3-16.5); p=0.015].Also, relapsed patients had higher Dnr clearance (CL)[median -546.54 (41.5-1632)vs. 329.3 (42.9-944.5); p=0.011] and lower DOL CL[median-9.8 (4.9-56)vs. median- 19.7 (6.1-57); p=0.015]than patients who did not relapse. IC50 of Dnr was higher in patients who relapsed (median-0.7 (0.02-1.46) vs. median- 0.23 (0.007-1.11); p=0.056) than in patients who did not relapse.To the best of our knowledge, this is the first population PK report in AML which is designed to evaluate various factors which might influence Dnr and DOL PK in AML. Though the number is small, our results suggest that plasma PK of Dnr influences clinical outcome in AML. Lower systemic exposure of Dnr in relapsed patients suggests that amount of drug required to completely eradicate the leukemic cells is not achieved and escalating dose might be an option to decrease relapse rates. Cellular pharmacokinetics of Dnr in these patients is ongoing in the lab, which will be more informative and help in prognosticating and dose adjustment for better treatment outcome.This data provides a probable biological basis for the previously reported clinical benefit of decreased relapses following the increase of the dose of DNR in induction to 90mg/m2/day (Tallman et al. NEJM 2009).Wide inter-individual variation in Dnr PK also suggests that this increased dose may not be necessary for all patients. Further studies are required to confirm this finding in a larger cohort of patients and to work towards strategies for TDM of Dnr in AML [Display omitted] [Display omitted] DisclosuresSrivastava:Octapharma: Consultancy, Other.

Transmembrane Transporters hOCT1 and SLCO1B3 Polymorphisms Could Have a Role in Patients Affected By Chronic Myeloid Leukemia Treated with Nilotinib

Background. Nilotinib represents an effective drug for the treatment of chronic myeloid leukemia after imatinib failure or, as more recently advocated, as first-line therapy. Its efficacy and tolerability allow the chronic administration of the drug, and some studies suggested that the greater benefit could be experienced when minimum plasma concentrations are above the limit of 1 mg/L. However, nilotinib is characterized by a non-negligible interpatient variability in its pharmacokinetics. The variable activity of transmembrane transporters should be not ruled out despite nilotinib has a lower substrate affinity for these proteins. In fact, recent in vitro studies demonstrated that SLCO1B3 and OCT3 are associated with nilotinib IC50 (Zimmermann, Clin Cancer Res 2013; Minematsu, Mol Cancer Ther 2011).Purpose. Therefore, the aim of this study was to investigate any possible influence of genetic polymorphisms in transmembrane transporters ABCB1, ABCG2, hOCT1 and SLCO1B3 on nilotinib pharmacokinetics, according to the procedures of the TIKlet protocol (ClinicalTrials.gov identifier: NCT 01860456).Methods. To accomplish with this objective, a population pharmacokinetic analysis was applied to investigate drug disposition in 21 men and 15 women (median age=62 years, range 38-84; Sokal high risk 15%, Hasford high risk 2%, EUTOS high risk 12%) who received nilotinib as second line therapy. Nilotinib plasma concentrations were measured by a validated UV-HPLC method, while patients’ genotype was obtained by real-time PCR on an ABI Prism 7900 HT instrumentation. The results were analysed through population pharmacokinetic modeling using NONMEM vers. 7.3.Results. With a median follow-up from nilotinib start of 42 months (range 3-86 months), 63% of patients were event-free, 25% of patients discontinuated treatment (2 deaths for MOF, other one for toxicity). After 3 months, all cases achieved the CHR, 82% presented a BCR-ABL1/ABL1 ratio <10%IS, and 74% achieved the MR3 by 12 months. Overall, 63% of treated cases achieved >MR4. When nilotinib plasma levels were measured, 80% of our patients had values higher than 1 mg/L. Results showed that elimination constant k10 was influenced by patient’s body mass index and the c.2677G>T/A polymorphism in exon 21 of the mdr1 gene. More interestingly, the polymorphism c.334T>G of the SLCO1B3 transporter was significantly associated with nilotinib bioavailability (F%). In particular, the wild-type genotype (TT) was associated with a 11% increase of F%, whereas the presence of at least one polymorphic allele (genotypes GT and GG) caused a reduction of F% of approximately 6%. Even if nilotinib plasma levels did not significantly influence its efficacy or toxicity, patients carrying the hOCT1 c.480C>G SNP (with lower influx pump activity) showed a shorter 3-year EFS (87% versus 54%, p=0.001) and cases with SLCO1B3 c.521 C allele showed a longer time to the CCyR (4.5 months vs 2.8, p=0.03) and to MR3 (14 months versus 9 months, p=n.s.).Conclusions. In conclusion, although the number of enrolled patients is limited, the present study suggests a role of transmembrane transporters hOCT1 and SLCO1B3 in the disposition of nilotinib. DisclosuresOff Label Use: Bendamustine.

Association of ABCG2 polymorphism with clinical efficacy of imatinib in patients with gastrointestinal stromal tumor.

Imatinib is a substrate of drug transporters and metabolizing enzymes, including members of the cytochrome P450 (CYP) system. Differences in imatinib pharmacokinetics among individuals might be influenced by genetic polymorphisms and be associated with variable clinical imatinib efficacy. This study sought to test how genetic polymorphisms can affect the clinical efficacy of imatinib and its blood levels in GIST patients. A total of 209 GIST patients who had received imatinib 400 mg daily were genotyped for six single-nucleotide polymorphisms in three genes (CYP3A5 6986A>G; ABCB1 1236C>T, 2677G>A/T, and 3435C>T; and ABCG2 34G>A and 421C>A) via blood samples. Progression-free survival (PFS) and imatinib plasma trough levels were evaluated and compared according to genotypes. With a median follow-up of 39.6 months (range 16.7-97.5 months), the estimated 5-year PFS rate was 67.5 % (95 % CI 59.9-75.1). Among the CYP3A5, ABCB1, and ABCG2 genotypes, ABCG2 421C>A was associated with PFS. The 5-year PFS rate in patients with the AA variant of ABCG2 421C>A (92.3 %; 95 % CI 77.8-100.0) was significantly superior to that of patients with CC/CA genotypes (65.0 %; 95 % CI 56.9-73.1; p = 0.047). For the imatinib trough levels, there were no statistically significant differences when comparing polymorphisms among all genotypes, even after adjusting for clinical factors, including sex, age, body surface area, hemoglobin, albumin, and creatinine clearance. The ABCG2 421C>A genetic variation could influence clinical efficacy in terms of PFS in patients with advanced GIST undergoing imatinib therapy.

Short communication: The gain-of-function Y581S polymorphism of the ABCG2 transporter increases secretion into milk of danofloxacin at the therapeutic dose for mastitis treatment

The ATP-binding cassette transporter ABCG2 restricts the exposure of certain drugs and natural compounds in different tissues and organs. Its expression in the mammary gland is induced during lactation and is responsible for the active secretion of many compounds into milk, including antimicrobial agents. This particular function of ABCG2 may affect drug efficacy against mastitis and the potential presence of drug residues in the milk. Previous in vitro and in vivo studies showed increased transport of several compounds, including fluoroquinolones, by the bovine ABCG2 Y581S polymorphism. Our main purpose was to study the potential effect of this bovine ABCG2 polymorphism on the secretion into milk of the antimicrobial danofloxacin administered at the therapeutic dose of 6mg/kg used for mastitis treatment. In addition, the effect of this polymorphism on the relative mRNA and protein levels of ABCG2 by quantitative real-time PCR and Western blot were studied. Danofloxacin 18% (6mg/kg) was administered to 6 Y/Y homozygous and 5 Y/S heterozygous cows. Danofloxacin levels in milk and milk-to-plasma concentration ratios were almost 1.5- and 2-fold higher, respectively, in Y/S cows compared with the Y/Y cows, showing a higher capacity of this variant to transport danofloxacin into milk. Furthermore, the higher activity of this polymorphism is not linked to higher ABCG2 mRNA or protein levels. These results demonstrate the relevant effect of the Y581S polymorphism of the bovine ABCG2 transporter in the secretion into milk of danofloxacin after administration of 6mg/kg, with potentially important consequences for mastitis treatment and for milk residue handling.

P1-5-4 - Association of Abcg2 Polymorphism with Plasma Concentrations of Axitinib in Patients with Renal Cell Carcinoma

Background: Axitinib is a selective inhibitor for VEGF receptors 1, 2, and 3 on renal cell carcinoma (RCC). The plasma concentrations and area under the blood concentration-time curve (AUC) of axitinib are known to correlate with response rate and survival rate in RCC patients. Breast cancer resistance protein (BCRP, ABCG2 gene) is an efflux ABC transporter, which is expressed at the apical membrane in intestine, and is involved in the absorption and excretion of various drugs. Several studies have demonstrated that ABCG2 polymorphism affects blood concentrations of oral anticancer drugs, especially molecular targeted drugs. To explore the relationship between pharmacokinetics and pharmacogenetics, we analyzed plasma concentrations of axitinib and ABCG2 polymorphism in RCC patients.Method: Eight RCC patients treated with axitinib at Nagoya University Hospital were enrolled in this study. All patients were orally administered 5mg axitinib twice a day. The blood samples were collected before (0 hr) and 0.5, 1, 2, 4 and 6 hr after administration of axitinib (6 points) on day 1 and day 8, respectively. The plasma concentrations of axitinb were analyzed by UPLC-MS/MS. The genetic polymorphism of ABCG2 was determined by real-time PCR. This study was approved by the ethical committee of Nagoya University Hospital, and all patients gave written informed consent.Result: The standard concentration-curve of axitinib in human plasma was linear in the range of 1-100 ng/mL. Intra- and inter-day precision ranged from 1.5 to 7.9% and accuracy were all less than 15%. The maximum concentration and AUC of axitinb in one patient carrying ABCG2 421A/A genotype were markedly higher than those carrying ABCG2 421C/A or C/C genotype on day 8.Conclusion: The plasma concentration of axitinb was analyzed accurately and reproducibly by UPLC-MS/MS. Our findings suggest that ABCG2 polymorphism, especially 421A/A genotype, may influence the plasma concentration of axitinib.

Epidermal Growth Factor Receptor (Egfr) and Abcg2 Polymorphisms and Treatment Outcome in the Randomized Phase III Torch Trial in Advanced Non-Small Cell Lung Cancer (Nsclc) Patients

ABSTRACT Aim: In the TORCH trial, molecularly unselected pts with advanced NSCLC were randomized to erlotinib or cisplatin + gemcitabine (CisGem) as first line within planned treatment sequences. To confirm previous data or explore new biomarkers, polymorphisms potentially affecting erlotinib activity (EGFR-216G > T [EGFR216], EGFR-191C > A [EGFR191], EGFR intron 1 CA-dinucleotide-repeat [CADR], ABCG2 + 421C > A [ABCG2]) were tested and the interaction with treatment was studied. Methods: Genotyping was by Sanger sequencing and Taqman. Interaction between each polymorphism and treatment outcome was tested by Cox model for progression-free survival (PFS) and by Zelen exact test for response rate (RR) and toxicity (skin and diarrhoea). Results: EGFR216 (known in 240 pts): G/G 32%, T/G 43%, T/T 25%. EGFR191 (240 pts): C/C 81%, A/C 17%, A/A 2%. ABCG2 (257 pts): C/C 85%, A/C 14%, A/A 1% (A/- 15%). CADR (262 pts): short/short (S/S) 28%, long/short 31%, long/long 40%. EGFR216 and EGFR191 had no significant interaction with treatment outcomes. ABCG2 polymorphism has no interaction with RR and toxicity but significantly affects treatment effect on PFS (interaction p = 0.039). HR (erlotinib vs CisGem) 1.69 (95% CI 1.28 – 2.23) in ABCG2 C/C and 0.71 (95% CI 0.34 – 1.47) in ABCG2 A/-. HR for ABCG2 A/- vs C/C was 0.68 (95% CI 0.40 – 1.14) and 1.47 (95%CI 0.90-2.44) in erlotinib and Cis/Gem arm respectively. CADR polymorphism was associated with skin toxicity but not diarrhoea: erlotinib produced more severe skin toxicity in CADR S/S pts (20% vs 6%, odds ratio 4.15, 95% CI 1.30-13.25, p = 0.013), while no severe skin toxicity was reported with CisGem. Conclusions: TORCH data: (a) do not confirm previous evidence on the value of EGFR216 as predictive of EGFR TKI effect; (b) confirm no value of EGFR191; (c) suggest that erlotinib efficacy might be higher in ABCG2 A/- cases; and (d) suggest that skin toxicity of erlotinib might be higher in CADR S/S cases. Disclosure: M. Di Maio and C. Gridelli: acted as consultant for Eli Lilli, Roche and received honoraria from Eli Lilli, Roche; M. Tsao: acted as consultant for AstraZeneca, Roche; he received honoraria from AstraZeneca, Roche and he received a research funding from Roche; C.A. Butts: acted as consultant for Roche and received honoraria from Roche; R. Feld: acted as consultant for Roche, received honoraria from Roche and received a research funding from Roche; F. Perrone: received honoraria from Roche and received a research funding from Roche. All other authors have declared no conflicts of interest.

Effects of the ABCG2 and ABCB1 drug transporter polymorphisms on the pharmacokinetics of bicalutamide in humans

BackgroundsBicalutamide is an oral non-steroidal anti-androgen used in the treatment of prostate cancer. Drug transporters P-glycoprotein encoded by ABCB1 and breast cancer resistance protein (BCRP) encoded by ABCG2 are involved in the transportation of bicalutamide and its treatment failure. We evaluated the roles of ABCB1 and ABCG2 genetic polymorphisms in the pharmacokinetics of bicalutamide in humans. MethodsAfter a single oral dose of 150mg bicalutamide was administered, plasma concentrations of bicalutamide were measured, and pharmacokinetic analyses were performed in 27 healthy subjects according to ABCB1 (c.1236C>T, c.2677G>T/A, and c.3435C>T) and ABCG2 (c.34G>A and c.421C>A). ResultsABCB1 polymorphisms did not affect the plasma levels of bicalutamide and the pharmacokinetic parameters did not differ among ABCB1 genotype groups. However, the ABCG2 c.421C>A polymorphism significantly influenced the plasma levels and pharmacokinetics of bicalutamide gene dose-dependently. ConclusionsThe ABCB1 genetic polymorphisms did not influence the pharmacokinetics of bicalutamide. However, ABCG2 c.421C>A significantly and gene dose-dependently influenced its pharmacokinetics, but c.34G>A did not.

Association of ABCG2 polymorphism with clinical efficacy of imatinib in patients with gastrointestinal stromal tumor.

10544 Background: Imatinib is a substrate of drug metabolizing enzymes, including those of the cytochrome P450 (CYP) system, and of several drug transporters. Differences in imatinib pharmacokineti...

High-dose methotrexate in Egyptian pediatric acute lymphoblastic leukemia: the impact of ABCG2 C421A genetic polymorphism on plasma levels, what is next?

High-dose methotrexate (HD-MTX) is a cornerstone antineoplastic drug in most treatment protocols of pediatric acute lymphoblastic leukemia (ALL). Among the membrane efflux transporters of MTX, the human breast cancer resistant protein is the second member of the G subfamily of ATP-binding cassette (ABC) efflux pump (ABCG2). A single-nucleotide polymorphism (SNP) in ABCG2, the exchange of C to A at position 421, represents 13 % in the Middle Eastern population. We studied the effect of this SNP on the plasma levels of HD-MTX in Egyptian pediatric ALL. Two hundred ALL patients were recruited from Children's Cancer Hospital Egypt-57357, and all were treated according to the St Jude Total XV protocol. Determination of plasma MTX levels was done at 23, 42 and 68 h. Genotyping of C421A of ABCG2 was done by polymerase chain reaction-restriction fragment length polymorphism. We found 14.5 % of the variant allele of the ABCG2 C421A SNP. The statistical association between ABCG2 421C>A SNP and the cutoff toxic plasma level of 24 h HD-MTX infusion at different time points tested was not statistically significant. There was no statistical significance between steady-state plasma concentration in patients with and without with this SNP. To date, this is the largest study on Egyptian ALL patients for this SNP. This study shows that there is no effect of ABCG2 421C>A on plasma concentrations of HD-MTX. Replacing candidate gene association studies with genome-wide studies of HD-MTX is now mandatory and is part of our research blueprint.

Association between statin-induced creatine kinase elevation and genetic polymorphisms in SLCO1B1, ABCB1 and ABCG2

Treatment with statins requires close monitoring of serum creatine kinase (CK) levels to prevent myopathy, a common and potentially serious dose-dependent adverse effect of these drugs. We have investigated the correlation between elevated CK levels and polymorphisms in the genes encoding transporters involved in statin disposition. Patients with and without statin-induced elevated serum CK levels were genotyped for polymorphisms in SLCO1B1 (SLCO1B1 A388G and SLCO1B1 T521C), ABCB1 (ABCB1 C1236T and ABCB1 C3435T) and ABCG2 (ABCG2 C421A). Patients carrying SLCO1B1 T521C or ABCB1 C1236T single nucleotide polymorphisms (SNPs) had an odds ratio (OR) for statin-induced elevated serum CK levels of 8.86 (p<0.01) and 4.67 (p<0.05), respectively, while patients carrying the SLCO1B1 A388G SNP had an OR of 0.24 (p<0.05). An arbitrary score based on genotype combination discriminated patients with and without CK elevation at a specificity of 97 % and a sensitivity of 39 %. Genotyping of the SLCO1B1, ABCB1 and ABCG2 genes deserves consideration as a clinical approach to improve statin safety while concomitantly reducing the burden of blood tests for CK measurements.

Genotype and allele frequencies of polymorphisms in ABCG2, PPARGC1A and OLR1 genes in indigenous cattle breeds in Turkey

Abstract This study was carried out to determine polymorphisms of four genes in South Anatolian Red (SAR) and East Anatolian Red (EAR) indigenous cattle breeds in Turkey. Single nucleotide polymorphisms (SNPs) monitored in this study are Y581S in ATP binding cassette sub family G member 2 (ABCG2) gene, c.1892T&gt;C and c.3359A&gt;C in peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) gene and g.8232C&gt;A in oxidized low-density lipoprotein receptor 1 (OLR1) gene. The frequency of the ancestral allele A of the ABCG2 gene Y581S polymorphism was found to be very high (SAR: 0.63; EAR: 0.64) in both cattle breeds. The CC genotypes of PPARGC1A gene c.1892T&gt;C (SAR: 0.65; EAR: 0.80) and OLR1 gene g.8232C&gt;A polymorphisms (SAR: 0.82; EAR: 0.86), which are associated with high milk fat percentage, had higher frequencies than those of the other genotypes. In conclusion, we might suggest that the allele distribution of the ABCG2 gene Y581S polymorphism can be the evidence indicating autosomal gene flow from zebu cattle to SAR and EAR cattle breeds.