ABCB1 Gene Variants Research Articles

Influence of CYP2C19, CYP2D6, and ABCB1 Gene Variants and Serum Levels of Escitalopram and Aripiprazole on Treatment-Emergent Sexual Dysfunction: A Canadian Biomarker Integration Network in Depression 1 (CAN-BIND 1) Study.

Treatment-emergent sexual dysfunction is frequently reported by individuals with major depressive disorder (MDD) on antidepressants, which negatively impacts treatment adherence and efficacy. We investigated the association of polymorphisms in pharmacokinetic genes encoding cytochrome-P450 drug-metabolizing enzymes, CYP2C19 and CYP2D6, and the transmembrane efflux pump, P-glycoprotein (i.e., ABCB1), on treatment-emergent changes in sexual function (SF) and sexual satisfaction (SS) in the Canadian Biomarker Integration Network in Depression 1 (CAN-BIND-1) sample. A total of 178 adults with MDD received treatment with escitalopram (ESC) from weeks 0-8 (Phase I). At week 8, nonresponders were augmented with aripiprazole (ARI) (i.e., ESC + ARI, n = 91), while responders continued ESC (i.e., ESC-Only, n = 80) from weeks 8-16 (Phase II). SF and SS were evaluated using the sex effects (SexFX) scale at weeks 0, 8, and 16. We assessed the primary outcomes, SF and SS change for weeks 0-8 and 8-16, using repeated measures mixed-effects models. In ESC-Only, CYP2C19 intermediate metabolizer (IM) + poor metabolizers (PMs) showed treatment-related improvements in sexual arousal, a subdomain of SF, from weeks 8-16, relative to CYP2C19 normal metabolizers (NMs) who showed a decline, F(2,54) = 8.00, p < 0.001, q = 0.048. Specifically, CYP2C19 IM + PMs reported less difficulty with having and sustaining vaginal lubrication in females and erection in males, compared to NMs. Furthermore, ESC-Only females with higher concentrations of ESC metabolite, S-desmethylcitalopram (S-DCT), and S-DCT/ESC ratio in serum demonstrated more decline in SF (r = -0.42, p = 0.004, q = 0.034) and SS (r = -0.43, p = 0.003, q = 0.034), respectively, which was not observed in males. ESC-Only females also demonstrated a trend for a correlation between S-DCT and sexual arousal change in the same direction (r = -0.39, p = 0.009, q = 0.052). CYP2C19 metabolizer phenotypes may be influencing changes in sexual arousal related to ESC monotherapy. Thus, preemptive genotyping of CYP2C19 may help to guide selection of treatment that circumvents selective serotonin reuptake inhibitor-related sexual dysfunction thereby improving outcomes for patients. Additionally, further research is warranted to clarify the role of S-DCT in the mechanisms underlying ESC-related changes in SF and SS. This CAN-BIND-1 study was registered on clinicaltrials.gov (Identifier: NCT01655706) on 27 July 2012.

ABCB1 Gene Variants and Antidepressant Treatment Outcomes: A Systematic Review and Meta-Analysis Including Results from the CAN-BIND-1 Study.

The P-glycoprotein efflux pump, encoded by the ABCB1 gene, has been shown to alter concentrations of various antidepressants in the brain. In this study, we conducted a systematic review and meta-analysis to investigate the association between six ABCB1 single-nucleotide polymorphisms (SNPs; rs1045642, rs2032582, rs1128503, rs2032583, rs2235015, and rs2235040) and antidepressant treatment outcomes in individuals with major depressive disorder (MDD), including new data from the Canadian Biomarker and Integration Network for Depression (CAN-BIND-1) cohort. For the CAN-BIND-1 sample, we applied regression models to investigate the association between ABCB1 SNPs and antidepressant treatment response, remission, tolerability, and antidepressant serum levels. For the meta-analysis, we systematically summarized pharmacogenetic evidence of the association between ABCB1 SNPs and antidepressant treatment outcomes. Studies were included in the meta-analysis if they investigated at least one ABCB1 SNP in individuals with MDD treated with at least one antidepressant. We did not find a significant association between ABCB1 SNPs and antidepressant treatment outcomes in the CAN-BIND-1 sample. A total of 39 studies were included in the systematic review. In the meta-analysis, we observed a significant association between rs1128503 and treatment response (T vs. C-allele, odds ratio=1.30, 95% confidence interval=1.15-1.48, P value (adjusted)=0.024, n=2,526). We did not find associations among the six SNPs and treatment remission nor tolerability. Our findings provide limited evidence for an association between common ABCB1 SNPs and antidepressant outcomes, which do not support the implementation of ABCB1 genotyping to inform antidepressant treatment at this time. Future research, especially on rs1128503, is recommended.

ABCB1 gene variants as risk factors and modulators of age of onset of demyelinating disease in Mexican patients.

The C1236T, G2677T/A, and C3435T variants of the ABCB1 gene alter the functioning of P-glycoprotein and the transport of endogenous and exogenous substances across the blood-brain barrier, and act as risk factors for some neurodegenerative diseases. This study aimed to determine the association between demyelinating disease and the C1236T, G2677T/A, and C3435T variants of ABCB1 and its haplotypes and combinations of genotypes. Polymerase chain reaction with restriction fragment length polymorphism analysis (PCR-RFLP) and Sanger sequencing were used to genotype 199 patients with demyelinating disease and 200 controls, all Mexicans of mixed race; frequencies of alleles, genotypes, haplotypes, and genotype combinations were compared between patients and controls. We conducted a logistic regression analysis and calculated chi-square values and 95% confidence intervals (CI); odds ratios (OR) were calculated to evaluate the association with demyelinating disease. The TTT and CGC haplotypes were most frequent in both patients and controls. The G2677 allele was associated with demyelinating disease (OR: 1.79; 95% CI, 1.12-2.86; P = .015), as were the genotypes GG2677 (OR: 2.72; 95% CI, 1.11-6.68; P = .025) and CC3435 (OR: 1.82; 95% CI, 1.15-2.90; P = .010), the combination GG2677/CC3435 (OR: 2.02; 95% CI, 1.17-3.48; P = .010), and the CAT haplotype (OR: 0.21; 95% CI, 0.05-0.66; P = .001). TTTTTT carriers presented the earliest age of onset (23.0 ± 7.7 years, vs 31.6 ± 10.7; P = .0001). The GG2677/CC3435 genotype combination is associated with demyelinating disease in this sample, particularly among men, who may present toxic accumulation of P-glycoprotein substrates. In our study, the G2677 allele of ABCB1 may differentially modulate age of onset of demyelinating disease in men and women.

Impact of ABCB1, ABCC1, ABCC2, and ABCG2 variants in predicting prognosis and clinical outcomes of north Indian lung cancer patients undergoing platinum-based doublet chemotherapy.

ABC transporters are membrane proteins expressed in the lungs and are crucial for efflux of various chemotherapeutic agents. Polymorphisms of ABC transporters have a certain impact on the transporter activity because their expression levels may influence the extent and longevity of chemotherapeutic drug outflow, affecting patient outcomes. The present study aimed to assess the impact of ABCB1, ABCC1/2, and ABCG2 gene variants in predicting prognosis and clinical outcomes in lung carcinoma patients. In total, 502 lung cancer patients undergoing platinum-based chemotherapy were recruited in this prospective study. Genotyping of ABCB1 (C1236 T, C3435 T, and G2677 T/A), ABCC1 (G3173 A and G2168 A), ABCC2 (G4544 A), and ABCG2 (C421 A) polymorphisms in Northern Indian lung carcinoma patients were evaluated using polymerase chain reaction-restriction fragment length polymorphism analysis. Poor survival outcomes were noted in patients carrying a heterozygous genotype (CT) for the ABCB1 C1236 T polymorphism compared to the wild-type genotype (CC) (p = 0.04). The mutant genotype (AA) for ABCC1 G3173 A exhibited a lower median survival time compared to the reference genotype (GG) (p = 0.009). Lower survival was observed in individuals carrying a heterozygous genotype (GA) for ABCC2 G4544 A polymorphism compared to the wild-type genotype (GG) (p = 0.017). Small cell lung cancer patients with the ABCB1 G2677 A polymorphism having a heterozygous genotype (GA) showed poor survival compared to the wild-type genotype (GG) (p = 0.03). For ABCC1 G3173 A, adenocarcinoma patients having a mutant genotype (AA) had reduced survival compared to the wild-type (GG) genotype (p = 0.03). For ABCB1 C3435 T, individuals carrying a heterozygous (CT) (p = 0.018) and mutant (TT) genotype (p = 0.007) had poor survival compared to the wild-type (CC) genotype in patients treated with pemetrexed and cisplatin. The patients administered cisplatin and irinotecan and having mutant alleles (AA) for the ABCB1 G2677 A polymorphism showed a lower survival compared to the individuals carrying wild-type alleles (GG) (p = 0.009). Our findings suggest that ABCB1 C1236 T, ABCB1 C3435 T, ABCB1 G2677 A, ABCC1 G3173 A, and ABCC2 G4544 A are involved in predicting prognosis. Genotyping of the ABC polymorphism is essential for predicting prognosis in lung carcinoma patients.

P256. ABCB1 Gene Variants and Antidepressant Response and Tolerability: A Systematic Review and Meta-Analysis Including Results From the CAN-BIND-1 Cohort

The p-glycoprotein efflux pump, encoded by the ABCB1 gene, has been shown to alter concentrations of various antidepressants in the brain. In this study, we investigated the association between selected ABCB1 single nucleotide polymorphisms (SNPs) and antidepressant treatment outcomes, including new and unpublished data from the Canadian Biomarker and Integration Network for Depression (CAN-BIND-1) cohort.

The Relationship of ABCB1/MDR1 and CYP1A1 Variants with the Risk of Disease Development and Shortening of Overall Survival in Patients with Multiple Myeloma.

(1) Background: The aim of our study was to analyze the possible relationship of ABCB1 and CYP1A1 gene variants with susceptibility and outcome of multiple myeloma (MM); (2) Methods: Genomic DNA samples from 110 newly-diagnosed MM patients and 100 healthy blood donors were analyzed by methods-PCR-RFLP (for ABCB1 3435C > T, CYP1A1 6235T > C—m1), automated DNA sequencing (for ABCB1 1236C > T, 2677G > T/A) and allele-specific PCR (for CYP1A1 4889A > G—m2); (3) Results: The genotypic frequencies of CYP1A1 4889A > G variant were not in Hardy-Weinberg equilibrium for MM patients. The presence of m1 and m2 CYP1A1 alleles decreased the risk of MM—OR = 0.49 (p = 0.011) and OR = 0.27 (p = 0.0003), respectively. In turn, TT genotype (ABCB1 2677G > T/A) increased the risk of this disease (p = 0.007). In the multivariate Cox analysis CT + TT genotypes (ABCB1 3435C > T) were associated with decreased risk of death (HR = 0.29, p = 0.04). In log-rank test in patients with CT genotype (ABCB1 3435C > T) was observed association of overall survival with the type of treatment; (4) Conclusions: Our findings suggest that T-alleles of ABCB1 2677G > T/A and m1/m2 alleles of CYP1A1 affected the susceptibility of MM. Moreover, T-allele of ABCB1 3435C > T might be independent positive prognostic factor in MM.

Lack of Association between C1236T, G2677T/A and C3435T Variants of the ABCB1 Gene and Imatinib Response in Iranian Chronic Myeloid Leukemia Patients

Imatinib introduction caused to improve the clinical outcomes of chronic myeloid leukemia (CML) patients. Despite the significant effects of Imatinib, pharmacogenetic variables induced treatment resistant is also observed.. Imatinib is known as a P-glycoprotein (P-gp) efflux pump substrate encoded by the ABCB1 gene. The ABCB1 C1236T, G2677T/A and C3435T variants are possibly correlated with interindividual variation in pharmacokinetic response to Imatinib therapy. The present study aimed to examine the effect of ABCB1 gene variants on the therapeutic response of Imatinib in CML patients. Sixty-nine Iranian CML patients treated with Imatinib or Nilotinib were selected and divided into two groups of sensitive and resistant to Imatinib. C1236T and G2677T/A variants were genotyped by high resolution melting (HRM) analysis, and C3435T variant was genotyped using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). Then, the results were compared between the two groups of patients. Our results showed that there were no significant differences between C1236T, G2677T/A and C3435T variants of ABCB1 gene and clinical response to Imatinib in the Iranian CML patients. According to the results of this study, genotyping of ABCB1 C1236T, G2677T/A and C3435T variants couldn’t help to predict the outcomes of Imatinib treatment in CML patients. So, these variants are not useful to make decisions about treatment, but it is suggested to do further investigations.

Influence of ABCB-1, ERCC-1 and ERCC-2 gene polymorphisms on response to capecitabine and oxaliplatin (CAPOX) treatment in colorectal cancer (CRC) patients of South India.

High interindividual response variability was reported with capecitabine and oxaliplatin (CAPOX) regimen in colorectal cancer (CRC). The single nucleotide polymorphisms (SNPs) of the genes related to drug efflux transport (ABCB1) and DNA repair (ERCC) could result in altered tumour response. Hence, this study was designed to assess the influence of ABCB1, ERCC-1 and ERCC-2 gene polymorphisms on tumour response to CAPOX treatment in CRC patients of South Indian origin. A total of 145 newly diagnosed CRC patients were included in the final analysis. Response to CAPOX treatment in the adjuvant setting was assessed in terms of disease-free survival rate (DFSR) and overall survival rate (OSR) at 3years, whereas in the palliative setting, the response was assessed as progression-free survival rate (PFSR) and OSR at 3years. Five millilitres of the venous blood sample was collected from each patient for genomic DNA extraction by the manual phenol-chloroform method. Genotyping and allelic discrimination analysis were done using real-time PCR (RT-PCR). With ABCB1 gene polymorphism rs1045642 (A>G), patients with AG/GG genotype showed better DFSR [P value=.02, OR=2 (CI: 1.5-3)] and PFSR [P value=.02, OR=1.6 (CI: 1.1-2.5)] when compared to AA genotype in the adjuvant and palliative settings, respectively. Similarly with rs1128503 (A>G) polymorphism, patients with AG/GG genotype were found to have better DFSR [P value=.02, OR=1.9 (CI: 1.3-3)] and PFSR [P value=.01, OR=2 (CI: 1.1-3.7)] when compared to AA genotype. However, we did not find any association between CAPOX response and ABCB1 gene polymorphisms in a binary logistic regression when non-genetic predictors were considered for analysis. We did not find any association with ERCC1 (rs11615 A>G) and ERCC2 (rs13181 T>G) gene polymorphisms with respect to CAPOX response in either of the treatment settings. The response to CAPOX treatment was found to be influenced by the ABCB1 gene variants (rs1128503 and rs1045642), thereby strengthening their predictive role. No association was found between ERCC1 (rs11615 A>G), ERCC2 (rs13181 T>G) gene polymorphisms and tumour response to CAPOX treatment in CRC patients of South Indian origin.

Genetic variation in the ABCB1 gene associated with post treatment lyme disease syndrome status

Post Treatment Lyme Disease Syndrome (PTLDS) poses a difficult to understand health issue. This multi-centered, randomized control trial studied the possible correlation between ABCB1 (MDR1) gene variants and the incidence of PTLDS in affected patients. Genomic DNA was isolated and analyzed for four ABCB1 gene SNPs (rs1128503, rs1045642, rs2235067, and rs4148740). Significant findings include the association of rs1128503 TC variant with PTLDS status. Additionally, the rs1128503+ rs1045642+ rs2235067 SNP combination increased rs1128503 genotype TC significance to 3.83 times the rs1128503 genotype CC. The TT variant of rs4148740 in conjunction with rs1128503 reduced the odds ratio and appeared to convey a PTLDS protective status to the rs1128503 TC variant.

Prolactin levels: sex differences in the effects of risperidone, 9-hydroxyrisperidone levels, CYP2D6 and ABCB1 variants.

The role of sex on the association of plasma prolactin levels with risperidone (R) and 9-hydroxyrisperidone (9-OHR) concentrations is investigated. Plasma R and prolactin concentrations, CYP2D6 and exon 21 and 26 ABCB1 gene variants were studied in 110 patients. In females, a 1ng/ml increase in R levels was associated with a significant 1.02% increase in prolactin levels. In males, a 1ng/ml increase in 9-OHR levels was associated with a significant 1.18% increase in prolactin levels. ABCB1 haplotype 12 had significant but opposite effects in males and females. In the combined sample, 9-OHR, but not R levels had significant effects on prolactin levels. Genes had sex-specific effects on risperidone-associated prolactin elevations.

Pharmacogenetics of post-transplant diabetes mellitus in children with renal transplantation treated with tacrolimus.

Post-transplant diabetes mellitus (PTDM) is a major complication of immunosuppressive therapy, with many risk factors reported in adults with renal transplantation. The objective of this study was to investigate potential non-genetic and genetic risk factors of PTDM in children with renal transplantation treated with tacrolimus. A national database was screened for patients developing PTDM within 4years following tacrolimus introduction. PTDM was defined as glucose disorder requiring anti-diabetic treatment. PTDM patients were matched to "non-PTDM" control transplanted children according to age, gender, and duration of post-transplant follow-up. Patients were genotyped for six selected genetic variants in POR*28 (rs1057868), PPARa (rs4253728), CYP3A5 (rs776746), VDR (rs2228570 and rs731236), and ABCB1 (rs1045642) genes, implicated in glucose homeostasis and tacrolimus disposition. Among the 98 children with renal transplantation enrolled in this multicentre study, 18 developed PTDM. None of the clinical and biological parameters was significant between PTDM and control patients. Homozygous carriers of POR*28 or wild-type ABCB1 (rs1045642) gene variants were more frequent in PTDM than in control patients with differences close to significance (p= 0.114 and p= 0.066 respectively). A genetic score based on these variants demonstrated that POR*28/*28 and ABCB1 CC or CT genotype carriers were at a significantly higher risk of developing PTDM after renal transplantation. Identification of PTDM risk factors should allow clinicians to allocate the best immunosuppressant for each patient with renal transplantation, and improve care for patients who are at a higher risk.

The predictive value of ABCB1, ABCG2, CYP3A4/5 and CYP2D6 polymorphisms for risperidone and aripiprazole plasma concentrations and the occurrence of adverse drug reactions.

We investigated in ninety Caucasian pediatric patients the impact of the main polymorphisms occurring in CYP3A, CYP2D6, ABCB1 and ABCG2 genes on second-generation antipsychotics plasma concentrations, and their association with the occurrence of adverse drug reactions. Patients with the CA/AA ABCG2 genotype had a statistically significant lower risperidone plasma concentration/dose ratio (Ct/ds) (P-value: 0.007) and an higher estimated marginal probability of developing metabolism and nutrition disorders as compared to the ABCG2 c.421 non-CA/AA genotypes (P-value: 0.008). Multivariate analysis revealed that the ABCG2 c.421 CA/AA genotype was found associated to a higher hazard (P-value: 0.004) of developing adverse drug reactions classified as metabolism and nutrition disorders. The ABCB1 2677TT/3435TT genotype had a statistically significant lower aripiprazole Ct/ds if compared with patients with others ABCB1 genotypes (P-value: 0.026). Information obtained on ABCB1 and ABCG2 gene variants may result useful to tailor treatments with these drugs in Caucasian pediatric patients.

Prognostic Value and Implication for Chemotherapy Treatment of ABCB1 in Epithelial Ovarian Cancer: A Meta-Analysis.

BackgroundChemotherapy resistance is reported to correlate with up-regulation of anti-tumor agent transporter ABCB1 (p-gp) in epithelial ovarian cancer (EOC), but the results remain controversial. To reconcile the results, a systematic review followed by meta-analysis was performed to assess the association between high ABCB1 status or ABCB1 gene variants and overall survival (OS), progression free survival (PFS), and total response rate (TR) in patients with EOC.Materials and MethodsElectronic searches were performed using Pubmed, EMBASE, Web of Science and Chinese Wanfang databases from January 1990 to February 2016. Summary hazard ratio (HR), risk ratio (RR) and 95% confidence intervals (CIs) were combined using fixed or random-effects models as appropriate.ResultsThirty-eight retrospective studies of 8607 cases qualified for meta-analysis were identified. Our results suggested that ABCB1 over-expression was significantly associated with unfavorable OS (HR = 1.54; 95% CI, 1.25–1.90), PFS (HR = 1.49; 95% CI, 1.22–1.82) and TR (RR = 0.63; 95% CI, 0.54–0.75). After adjustment for age, clinical stage, residual disease, histological type and tumor grade, high ABCB1 status remained to be a significant risk factor for adverse OS and PFS. Patients with recurrent ABCB1 positivity suffered from poorer OS than those with primary ABCB1 positivity. However, stratified by chemotherapy regimen, inverse correlation between high ABCB1 status and poor OS, PFS and TR were only found in patients underwent platinum-based chemotherapy but not in patients received standard platinum/paclitaxel-based chemotherapy. No evidence was found for any association between ABCB1 gene polymorphisms and OS, PFS or TR.ConclusionHigh ABCB1 status is significantly associated with chemo-resistance and poor prognosis in patients with EOC. Large-scale, prospective studies are needed to assess the clinical value of ABCB1 expression in EOC more accurately.

Association of ABCB1 gene variants, plasma antidepressant concentration, and treatment response: Results from a randomized clinical study

P-glycoprotein, encoded by the ABCB1 gene, functions as an ATP-driven efflux pump in the blood–brain barrier, extruding its substrates and thereby limiting their passage into the brain. ABCB1 polymorphisms predicted antidepressant drug response: Minor allele carriers of SNPs rs2032583 and rs2235015 had higher remission rates than major allele homozygotes. The aim of the current study was to evaluate an ABCB1 genotype-dependent efficacy of a quick dose escalation strategy.Depressed inpatients (n = 73) treated with antidepressants that are P-glycoprotein substrates were randomly assigned to a standard or high dose condition for 28 days. HAM-D scores, adverse effects and plasma antidepressant concentration were measured weekly and tested among two intronic SNPs rs2032583 and rs2235015. A treatment as usual control sample (n = 128) was retrospectively matched to the study group by gender, age, and diagnosis.There was a significant interaction of genotype x plasma antidepressant concentration: Minor allele carriers of rs2032583 [F(1,65) = 7.221, p = 0.009] and rs2235015 [F(1,65) = 4.939, p = 0.030] whose plasma drug concentration were within recommended range had a greater symptom reduction at study endpoint which exceeded the therapeutic benefit of the treatment as usual group [for rs2032583: F(1,163) = 4.366, p = 0.038]. Minor allele carriers of rs2032583 with high plasma drug levels had more sleep-related side effects than major allele homozygotes with high plasma drug levels.The treatment of MDD can be optimized by ABCB1 genotyping combined with monitoring of plasma drug concentrations: For minor allele carriers of rs2032583 and rs2235015, plasma antidepressant levels should not exceed the recommended range in order to obtain optimal treatment outcome.

Genetic variability in ABCB1, occupational pesticide exposure, and Parkinson’s disease

BackgroundStudies suggested that variants in the ABCB1 gene encoding P-glycoprotein, a xenobiotic transporter, may increase susceptibility to pesticide exposures linked to Parkinson's Disease (PD) risk. ObjectivesTo investigate the joint impact of two ABCB1 polymorphisms and pesticide exposures on PD risk. MethodsIn a population-based case control study, we genotyped ABCB1 gene variants at rs1045642 (c.3435C/T) and rs2032582 (c.2677G/T/A) and assessed occupational exposures to organochlorine (OC) and organophosphorus (OP) pesticides based on self-reported occupational use and record-based ambient workplace exposures for 282 PD cases and 514 controls of European ancestry. We identified active ingredients in self-reported occupational use pesticides from a California database and estimated ambient workplace exposures between 1974 and 1999 employing a geographic information system together with records for state pesticide and land use. With unconditional logistic regression, we estimated marginal and joint contributions for occupational pesticide exposures and ABCB1 variants in PD. ResultsFor occupationally exposed carriers of homozygous ABCB1 variant genotypes, we estimated odds ratios of 1.89 [95% confidence interval (CI): (0.87, 4.07)] to 3.71 [95% CI: (1.96, 7.02)], with the highest odds ratios estimated for occupationally exposed carriers of homozygous ABCB1 variant genotypes at both SNPs; but we found no multiplicative scale interactions. ConclusionsThis study lends support to a previous report that commonly used pesticides, specifically OCs and OPs, and variant ABCB1 genotypes at two polymorphic sites jointly increase risk of PD.

Genetic polymorphisms, efficiency and toxicity of cancer chemotherapy

Human reaction to drugs, including chemotherapeutics, is an extremely complex process, with many enzymes of different metabolic and signal transduction pathways involved. Despite the knowledge already gathered, the exact mechanisms responsible for individual patients’ responses to chemotherapy drugs, including adverse reactions, are still not clear. Cellular transport and detoxification systems evolved as natural protection against xeniobiotics and they process substrates that belong to diverse chemical classes. There is evidence that polymorphic variants in genes encoding proteins involved in influx, efflux and two metabolism phases (i.e. ABC and SLC transporters, CYP and GST enzymes family) can both influence chemotherapeutic regimes' effectiveness and toxicity. Also, because the drug-induced damages to nucleic acid structure are responsible for activating cell death programme, it is assumed that, apart from transport and detoxification systems, resistance to these drugs can also be the result of effective DNA repair systems, defective checkpoint activation and flawed recognition of DNA adducts. It is plausible that functional polymorphisms in genes encoding key proteins of said mechanisms (i.e. ERCC and XRCC families, p53, ATM) will influence cells’ sensitivity to drugs. Chemotherapeutic regimes are usually composed of non-crossing agents aimed at a variety of cellular targets and processes in order to overcome cells' resistance to single drugs, for example 5-fluorouracil, doxorubicin and cyclophosphamide are used as FAC regime in breast cancer, or carbo/cisplatin administered with paclitaxel in treatment of ovarian cancer. This approach substantially increases the chance of success of a treatment, but also increases the number of factors potentially responsible for treatment failure and/or severe adverse reactions. Consistently, insensitivity or oversensitivity to multidrug treatment has to be a result of global changes in activity of proteins involved in every, or some of the mechanisms responsible for used drugs transport, metabolism, and their specific impact on the cell. For FAC, it has been shown that pyrimidine analog 5-fluorouracil's effectiveness could be modulated in the presence of polymorphic variants in SLC22, CYP, and GST gene families. Similarly to 5-fluorouracil, polymorphisms in genes for CYPs could be responsible for different cells’ reaction to cyclophosphamide, and reduced drug detoxification rates could be connected to functional variants in GST isoform genes. For the ovarian cancer paclitaxel/cisplatin regime there is strong evidence that accumulation of several polymorphic variants is responsible for elevated risk of death and progression (PGR, ATM and ABCB1 gene variants). Such accumulation is also correlated with many symptoms of chemotherapy systemic toxicities, such as haematological - including neutropenia, gastro-intestinal and hepatological toxicity (polymorphisms in ATP7B and PGR genes). The search for genetic factors connected to the high risk of treatment failure and severe toxicity has become one of the foundations of personalised medicine. Simultaneous analysis of many genetic factors, which individually may have very subtle impact on the cellular processes and therefore may be omitted, allows the understanding of their cumulative impact on the chemotherapy response. Insight into the complex molecular mechanisms resulting in drug resistance or oversensitivity during cancer treatment, may be potentially relevant for the further research focused on developing drugs tailored to cancer patients’ genetic profile.

Optimizing antidepressant treatment dosage based on ABCB1 gene variants – Results from a randomized clinical study

The gene product of the ABCB1 gene, the P-glycoprotein (P-gp), functions as a custodian molecule in the blood-brain barrier extruding its substrates and thereby limiting their passage to the brain. ABCB1 polymorphisms rs2032583 and rs2235015 predicted the response to antidepressants with P-gp substrate properties (Uhr et al., 2008). The aim of this study was to evaluate an ABCB1 genotype-dependent efficacy of a quick dose-escalation strategy. Depressed inpatients (n = 73) treated with antidepressant that are P-gp substrates were randomly assigned to a standard or high dose condition for 28 days. HAM-D scores, adverse effects and plasma levels were measured weekly and tested among two intronic ABCB1 SNPs rs2032583 and rs2235015. A treatment as usual (TAU) control sample (n = 128) was retrospectively matched by gender, age, diagnosis. There was an interaction of genotype x plasma group: Minor allele carriers of rs2032583 whose plasma levels were within the recommended range had a greater symptom reduction than the TAU group [for rs2032583:F(1,163) = 4.366,p = 0.038]. Minor allele carriers in the high plasma group had more sleep disturbances than those in the normal plasma group and noncarriers. The treatment of MDD can be optimized by ABCB1 genotyping combined with monitoring of plasma drug concentration: For minor allele carriers of rs2032583 and rs2235015, antidepressant plasma levels should not exceed the recommended range in order to obtain optimal treatment outcome. This study was supported by HMNC GmbH

Role of SLCO1B1, ABCB1, and CHRNA1 gene polymorphisms on the efficacy of rocuronium in Chinese patients.

This study explored the role of SLCO1B1, ABCB1, and CHRNA1 gene polymorphisms on the efficacy and duration of action of rocuronium in Chinese patients. Two hundred seven unrelated Chinese patients scheduled for elective surgery were recruited, and 200 completed the study. Their ABCB1, SLCO1B1, and CHRNA1 genotypes were determined. Demographic and clinical non-genetic data also were collected. The SLCO1B1, ABCB1, and CHRNA1 variants did not affect the onset time of rocuronium. Clinical duration and recovery time of rocuronium were prolonged in patients with the ABCB1 rs1128503TT and SLCO1B1 rs2306283 AG and GG genotypes. We demonstrate that the SLCO1B1 and ABCB1 gene variants could affect the pharmacodynamics of rocuronium. The ABCB1 rs1128503 C>T genotype was the most important factor on the efficacy of rocuronium.

Association analysis of three ABCB1 (MDR1) gene variants (C1236T, G2677A/T and C3435T) and their genotype/haplotype combinations with the familial Mediterranean fever

1. Familial Mediterranean fever (FMF) is considered an autosomal recessive disorder, associated with a single gene named Mediterranean fever (MEFV). The aim of this study was to perform genotyping and haplotyping analysis of the multidrug resistance (ATP-binding cassette, subfamily B, member 1 – ABCB1) gene in FMF patients.2. Three ABCB1 gene polymorphisms (C1236T, G2677T/A and C3435T) were analyzed in 309 FMF patients and 250 healthy control subjects. All subjects were genotyped by PCR–restriction fragment length polymorphism analysis, and statistical analysis was performed using the Arlequin 3.1.1 and SPSS 16.0 software packages.3. The CT genotype frequency of the C3435T polymorphism (p = 0.003), the CT–GT–CT (C1236T–G2677T/A–C3435T) triple genotype (p = 0.001) and the C–G (C1236T–G2677T/A) haplotype (p = 0.030) were more common in the FMF patients. The CT–GG–CC triple genotype and T–G–C, C–T–T and T–G–T haplotypes (C1236T–G2677T/A–C3435T) were higher in the control subjects (p = 0.011, 0.001, 0.009 and 0.000, respectively). The CT–GG binary genotype and C–T and T–G haplotypes for C1236T–G2677T/A polymorphisms may have a high degree of protective effect against FMF (p = 0.0005, 0.002 and 0.000, respectively).4. Our study showed that genotypes and haplotypes of ABCB1 gene polymorphisms may affect patients’ FMF susceptibility.

The impact of APOL1, CAV1, and ABCB1 gene variants on outcomes in kidney transplantation: donor and recipient effects

Dramatic improvements have been seen in short-term kidney allograft survival over recent decades with introduction of more potent immunosuppressant medications and regimens. Unfortunately, improvements in long-term graft survival have lagged behind. The genomics revolution is providing new insights regarding the potential impact of kidney donor genotypes on long-term graft survival. Variation in the donor apolipoprotein L1 (APOL1), caveolin 1 (CAV1), and multi-drug resistance 1 encoding P-glycoprotein genes (ABCB1) are all associated with graft survival after kidney transplantation. Although the precise mechanisms whereby these donor gene variants confer risk for graft loss have yet to be determined, these findings provide novel opportunities for modifying interactive environmental factors and optimizing kidney allocation with the ultimate goal of improving long-term graft survival rates.