Association of MDR1 genotypes with susceptibility to colorectal cancer in older non-smokers

LncRNA <i>SNHG16</i> promotes colorectal cancer proliferation by regulating ABCB1 expression through sponging miR-214-3p

Mounting evidence indicates that long non-coding RNAs (lncRNAs) have critical roles in colorectal cancer (CRC) progression, providing many potential diagnostic biomarkers, prognostic biomarkers, and treatment targets. Here, we sought to investigate the role and underlying regulatory mechanism of lncRNA small nucleolar RNA host gene 16 (SNHG16) in CRC. The expressions of SNHG16 in CRC were identified by RNA-sequencing and quantitative reverse transcription PCR. The functions of SNHG16 were explored by a series of in vitro and in vivo assays (colony formation assay, flow cytometry assay, and xenograft model). Bioinformatics analysis, RNA fluorescencein situ hybridization and luciferase reporter assay were used to investigate the regulatory mechanism of effects of SNHG16. SNHG16 was found to be significantly elevated in human CRC tissues and cell lines. Functional studies suggested that SNHG16 promoted CRC cell growth both in vitro and in vivo. Mechanistically, we identified that SNHG16 is expressed predominantly in the cytoplasm. SNHG16 could interact with miR-214-3p and up-regulated its target ABCB1. This study indicated that SNHG16 plays an oncogenic role in CRC, suggesting it could be a novel biomarker and therapeutic target in CRC.

Association between ABCB1 (3435C>T) polymorphism and susceptibility of colorectal cancer: A meta-analysis

Studies on the relationship between ABCB1 3435C>T polymorphism (rs1045642) and colorectal cancer (CRC)susceptibility have yielded inconclusive results. To clarify this issue, we undertook a meta-analysis to investigate the relationship between rs1045642 and CRC risk.Three electronic scientific publication databases (Cochrane Library, Pubmed, Embase) were screened using specific search terms. Relevant literature was identified using literature traceability methods. Selected publications were evaluated according to the inclusion and exclusion criteria. Effect size information (odds ratio and the corresponding 95% confidence interval [CI]) was obtained following quality assessment and data extraction from the included publications, and a meta-analysis conducted. Statistical analysis was performed with the Stata sofz (Version 13.0) software.Overall, 17 case-control studies involving 7129 CRC patients and 7710 healthy control subjects satisfied the criteria for inclusion in the meta-analysis. There was no significant association between ABCB1 3435C>T polymorphism and CRC risk in any of the genetic models. In the CC versus CT model (I = 20.9%, Pheterogeneity = .276), CC versus CT + TT model (I = 45.6%, Pheterogeneity = .102) and CT versus CC + TT model (I = 17.8%, Pheterogeneity = .298) analyses, between-study heterogeneities were detected as significant in Asian populations. In the CT versus TT model (I = 24%, Pheterogeneity = .254) and CC + CT versus TT model (I = 0, Pheterogeneity = .55), between-study heterogeneities were found to be significant in groups of different populations.The meta-analysis described here suggests that the ABCB1 3435C>T polymorphism is not related to CRC susceptibility.

ADME pharmacogenetics: future outlook for Russia

This systematic review reflects the results of pharmacogenetic studies in the Russian Federation aimed at studying the genes involved in the drug biotransformation system. The works of Russian researchers found by us are mostly devoted to microsomal liver oxidation enzymes (metabolism) and membrane transporter systems (absorption and excretion). This review presents population-ethnic and associative clinical studies on the genes of the CYP450 system, noncytochrome oxidation enzymes ( SULT1A1, CES1), membrane transporter system genes ( ABCB1, SLCO1B1) and warfarin biotransformation enzymes ( VKORC1, GGCX). The information is structured in the form of 11 tables, divided by regions of the Russian Federation.

Common variants in glucuronidation enzymes and membrane transporters as potential risk factors for colorectal cancer: a case control study

Background

Associations between polymorphisms of UDP-glucuronosyltransferases (UGTs) or efflux transporters (e.g., P-glycoprotein and MRP2) and different types of cancer have been described, whereas the role of influx transporters (e.g. OATP1B1 and OATP2B1) has been seldom explored. The GenColon study investigated potential associations between variant alleles of UGTs, efflux and influx transporters and CRC.

Methods

Three hundred CRC cases were matched with 300 controls for age, sex and enrolment site. Fifteen SNPs in UGT1A6–9, UGT2B7, ABCB1, ABCC2, SLCO1B1 and SLCO2B1 genes were characterized using Taqman® PCR. Using multivariate conditional logistic regression, we investigated the relationships between CRC and “environmental” risk factors (physical activity, housing and working areas, consumption of red meat, tobacco, alcohol); genetic polymorphisms, in the study population and in the subgroups with “environmental” risk factors.

Results

No significant association was observed for the analyzed SNPs (or haplotypes). However, an increased CRC risk was found in carriers of the UGT1A8 rs1042597-G variant allele (additive risk OR = 3.39[1.29–8.89], p = 0.02951) in the subgroup of meat-consumers (n = 84), and in carriers of the ABCB1 rs1045642-T (exon26) variant allele (additive risk; OR = 1.89[1.10–3.39], p = 0.0257) in the “never alcohol consumption subgroup” (n = 125). In addition, as previously reported, the following CRC risk factors were identified: absence of physical activity (OR = 6.35[3.70–10.9], p < 0.0001), living or working in rural or mix area (OR = 2.50[1.48–4.23], p = 0.0006 and OR = 2.99[1.63–5.48], p = 0.004, respectively) and tobacco exposure >30 years (3.37[1.63–6.96], p = 0.0010).

Conclusions

Variant genotypes of influx transporters (OATP1B1 and 2B1) were not associated with CRC. This study confirmed the influence of lifestyle factors, but not the previously reported detrimental effect of SNPs in intestinal UGTs or efflux transporters, except for a UGT1A8 variant in subjects consuming meat and the exon 26 SNP of ABCB1 in the never alcohol consumption subgroup.

Trial registration

Registered in Direction Générale de la Santé the 1st July 2008 under the number DGS2008–0144.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3728-0) contains supplementary material, which is available to authorized users.

The importance of G2677T/A and C3435T polymorphisms of the MDR1 gene in the aetiology of colorectal cancer

Introduction

Colorectal cancer (CRC) is the most common cancer among patients, and its aetiology is still not precisely known. It is believed that 15–30% of colorectal cancers are genetically determined. P-glycoprotein (P-gp) encoded by the MDR1 gene in normal conditions plays an important role in the action of colon epithelial cells. However, the MDR1 polymorphism influences the P-gp expression and can weaken its effect against xenobiotics (procarcinogens) and increase the frequency of CRC.

Aim

To evaluate the correlation between the MDR1 C3435T and G2677T/A polymorphisms and the risk of colorectal cancer.

Material and methods

The study group with colorectal cancer included 47 women and 60 men while the control group consisted of 110 healthy patients. The diagnosis in patients suffering from CRC was confirmed by histopathological report. Genetic analysis was performed using PCR-RFLP method.

Results

We showed only a correlation between the frequency of CT and TT genotypes of C3435T polymorphism and the risk of colorectal cancer in younger age. There was no correlation between the C3435T and G2677T/A polymorphisms of the MDR1 gene and other clinical parameters.

Conclusions

Our findings suggest that T allele carriers of C3435T polymorphism have an increased risk of CRC. However, further studies are needed on a much larger number of patients and genes associated with metabolism and transport of xenobiotics including procarcinogens.

Colorectal cancer susceptibility: apparent gender-related modulation by ABCB1 gene polymorphisms

BACKGROUND

The ATP-binding cassette transporter B1 (ABCB1) gene codes for a membrane efflux pump localized in epithelial cells. Together with other Permeability-glycoproteins in the small and large intestine, its product represents a barrier against xenobiotics, bacterial toxins, drugs and other substances introduced with diet, including carcinogens. The aim of this investigation was to verify the possible contribution of ABCB1 single nucleotide polymorphisms (SNPs) to the genetic risk of colorectal cancer (CRC).

RESULTS

DNA obtained from the peripheral blood of 98 CRC patients and 100 healthy controls was genotyped for the three selected SNPs: 1236C > T (rs1128503), 2677G > T/A (rs2032582), and 3435C > T (rs1045642). Molecular data were analyzed to asses allele and haplotype association with CRC. No evidence of an association between ABCB1 alleles and CRC occurrence as a whole was found. However, ABCB1 showed either association with carcinoma of the sigmoid colon, and appeared able to influence the sex ratio among CRC patients. These two effects seemed to act independently based on multivariate analysis. We showed that ABCB1 polymorphisms were able to influence CRC susceptibility related to tumor localization and patient gender.

CONCLUSIONS

We suggest that sensitivity to undetermined risk factors could depend on the genetic background of ABCB1 locus, with a mechanism that also depends on patient gender.

Meta-Analysis of ABCB1 3435C>T Polymorphism and Colorectal Cancer

OBJECTIVE

Many studies have focused on the association between the ABCB1 3435C>T polymorphism and colorectal cancer (CRC) risk. However, the results were conflicting. The aim of this meta-analysis is to evaluate the precise association between this polymorphism and CRC risk.

METHODS

We formally reviewed the literature at Pubmed, EMBASE and the Cochrane Library with the key words as follows: ABCB1/MDR1/P-glycoprotein, polymorphism, colorectal and cancer/neoplasm/tumor. This meta-analysis was assessed by Review manager 5.0. The fixed-effects model was used to pool the odds ratios (OR) with 95% confidence intervals (CI) for CRC risk.

RESULTS

There were 8 studies identified. The pooled OR with 95% CI of CC+CT versus TT genotype of the ABCB1 3435C>T polymorphism for CRC risk was 1.01 [0.90-1.13]. The sensitivity analysis further confirmed the result. Heterogeneity and publication bias were not observed in this meta-analysis.

CONCLUSIONS

In summary, there was no significant association between the ABCB1 3435C>T polymorphism and CRC risk. Abbreviations used: the ATP-binding cassette, subfamily B, member 1 (ABCB1); multidrug resistance gene 1 (MDR1); P-glycoprotein (P-gp); colorectal cancer (CRC); single nucleotide polymorphisms (SNPs); odds ratio (OR); confidence interval (CI); Hardy-Weinberg equilibrium (HWE).

Association of ABCB1 genetic polymorphisms with susceptibility to colorectal cancer and therapeutic prognosis

AIM

To evaluate the association of ABCB1 gene polymorphisms with susceptibility to colorectal cancer (CRC) and clinical outcomes of CRC patients with chemotherapy.

PATIENTS & METHODS

A case-control study was performed on the C3435T, C1236T and G2677T/A polymorphisms in the ABCB1 gene in 1028 CRC patients and 1230 controls.

RESULTS

We observed that the ABCB1 C3435T and G2677T/A variants as well as the 3435T-1236T-2677T haplotype significantly increased the risk of CRC. The ABCB1 C3435T CT genotype had a significant effect on the time to recurrence (adjusted hazard ratio [HR; 95% CI]: 0.560 [0.355-0.882]; p = 0.012). Moreover, ABCB1 C1236T variant carriers displayed a longer overall survival after postoperative oxaliplatin-based chemotherapy (adjusted HR [95% CI]: 0.354 [0.182-0.692], 0.646 [0.458-0.910], respectively). In addition, 1236TT-2677TT-3435TT haplotype carriers showed a worse progression-free survival (adjusted HR [95% CI]: 1.477 [1.012-3.802]; p = 0.043) and recurrence-free survival (adjusted HR [95% CI]: 2.183 [1.253-3.802]; p = 0.006).

CONCLUSION

The ABCB1 polymorphisms might be a candidate pharmacogenomic factor to assess susceptibility and prognosis after oxaliplatin-based chemotherapy for CRC patients.

The association between polymorphisms in the MDR1 gene and risk of cancer: a systematic review and pooled analysis of 52 case-control studies

Background

The multidrug resistance (MDR) 1 gene encodes a 170-kDa membrane transporter called P-glycoprotein, which plays an important role in protecting cells against lipophilic xenobiotics by the way of an ATP-dependent cellular efflux mechanism. Three polymorphisms of MDR1, 3435C > T located in exon 26, 1236C > T in exon 12 and 2677G > T/A in exon 21 were the most extensively studied and were identified functionally important and ethnically diverse mapping to the gene region. Considering the potential influence of altering MDR1 activity, it is plausible that MDR1 polymorphisms might play a role in the development of cancer. Although the effects of MDR1 polymorphisms on susceptibility to human cancer have been investigated in many studies, the results still remain conflicting.

Methods

To resolve these conflicts, we performed a quantitative synthesis of the association between these three polymorphisms and cancer risk, including 52 studies (15789 cases and 20274 controls) for 3435C > T polymorphism, 10 studies (2101 cases and 2842 controls) for 1236C > T polymorphism and 18 studies (3585 cases and 4351 controls) for 2677G > T/A polymorphism.

Results

The stratified analyses for 3435C > T polymorphism, individuals with T-allele in 3435C > T had significantly higher ALL risks (TT versus CC: OR =1.286, 95% CI =1.123-1.474); significantly elevated risks were observed among Caucasian populations (TT versus CC: OR =1.276, 95% CI =1.112-1.464). When restricting the analysis to the source of controls, we found that HB (hospital-based) genetic models had higher risks (TT versus CC: OR =1.307, 95% CI =1.046-1.632), as well as in PB (population-based) genetic models (TT versus CC: OR =1.294, 95% CI =1.079-1.55).

The T/A-allele frequency of 2677G > T/A polymorphism was associated with higher risk of cancer (TT + TA + AA vs. GG: OR =1.348, 95% CI =1.031-1.762), significantly elevated risks were observed among Asian populations (TT + TA + AA vs. GG: OR =1.642, 95% CI =1.340-2.012), and elevated risks could be associated with PB models (TT + TA + AA vs. GG: OR =1.641, 95% CI =1.018-2.646).

Conclusions

Our meta-analysis suggested that 3435C > T polymorphism and 2677G > T/A polymorphism were associated with cancer risk when all studies were pooled together, while 1236C > T polymorphism not.

Association between the C3435T polymorphism of ABCB1/MDR1 gene (rs1045642) and colorectal cancer susceptibility : a meta-analysis based on 11,339 subjects

The association between ABCB1/MDR1 C3435T polymorphism and colorectal cancer has been evaluated. However, the results of these studies on the association remain inconsistent. To derive a more precise estimation of the relationship, a meta-analysis was performed. A comprehensive search was conducted to identify the eligible studies of ABCB1/MDR1 C3435T polymorphism and colorectal cancer risk. Summary odds ratios (OR) and 95 % confidence interval (CI) for ABCB1/MDR1 C3435T polymorphism and colorectal cancer were calculated. Statistical analysis was performed with the Stata (Version 12.0). Thirteen case-control studies, a total of 11,339 persons including 5,485 cases and 5,854 controls, met the included criteria and thus were selected. Collectively, the results of the present study suggest that there were no significant associations of ABCB1/MDR1 C3435T polymorphism with colorectal cancer observed for all comparison models. In the subgroup analysis, the same results were detected for both Caucasian and Asian populations. The results of this meta-analysis suggest that ABCB1/MDR1 C3435T polymorphism might be not related to colorectal cancer susceptibility.

Associations between the functional polymorphisms in the ABCB1 transporter gene and colorectal cancer risk: a case-control study in Turkish population

Colorectal cancer is among the most common cancer types in the world and its etiology involves the interaction of genetic and environmental factors. ABCB1 is highly expressed in the apical surface of colonic epithelial cells and acts as an efflux pump by transporting toxic endogenous substances, drugs and xenobiotics out of cells. ABCB1 polymorphisms may either change its protein expression or alter its function. Several studies have reported a possible association between ABCB1 variants and colorectal cancer, but no consistent conclusion has been arrived at. Therefore, we aimed to investigate the relationship between colorectal cancer and the functional common variants of ABCB1 (1236C > T; 2677G > T/A; 3435C > T). The distributions of the variants were determined in 103 patients with colorectal cancer and 150 healthy volunteers using polymerase chain reaction-restriction fragment length polymorphism methods. ABCB1 1236C > T was statistically significantly associated with colorectal cancer risk (OR, odd ratio = 1.91; 95% CI, confidence interval = 1.09-3.35; p = 0.034). In haplotype-based analysis, the proportion of individuals with the ABCB1 haplotype C1236-G2677-T3435 was significantly more common in patients than in controls (OR = 11.96; 95% CI = 2.59-55.32; p = 0.0004). We believe that the findings may be beneficial to the development of efficacious preventive strategies and therapies for colorectal cancer.

ABCB1/MDR1 gene polymorphism and colorectal cancer risk: a meta-analysis of case-control studies

AIM

ABCB1/MDR1 protein is found in high concentrations on the apical surfaces of colonic epithelial cells. It acts as an efflux pump by transporting toxic endogenous substances, drugs and xenobiotics out of cells. Polymorphisms in the ABCB1/MDR1 gene may either change expression of the ABCB1/MDR1 protein or alter its function, suggesting its possible association with colorectal cancer. Several studies have reported a relationship between ABCB1 gene polymorphisms and colorectal cancer risk, but no consistent conclusion has been reached. We therefore conducted a meta-analysis to identify any association between the ABCB1 gene and CRC risk.

METHOD

PubMed, Embase, Google Scholar, Cbmdisc and CNKI were searched for studies on the relationship of ABCB1/MDR1 gene SNPs and the incidence of colorectal cancer. Eligible articles were included for data extraction. The main outcome was the frequency of ABCB1/MDR1 gene SNPs among cases and controls. Comparison of the distribution of SNPs was performed mainly using Review Manager 5.0.

RESULTS

Ten, four and two trials were identified that focussed on the ABCB1 gene SNPs rs1045642, rs2032582 and rs3789243, respectively. A total of 3175 cases and 3715 controls were included. The meta-analysis, stratified by ethnicity or population source, indicated no association between the ABCB1 gene rs1045642 polymorphism and colorectal cancer risk. However, when the study by Bae et al. was removed from the analysis, there was some evidence to indicate a higher T-allele frequency in Asian colorectal cancer patients (OR = 1.30, 95% CI: 1.02-1.67, P = 0.03). Neither ABCB1 rs2032582 nor ABCB1 rs3789243 indicated an association with colorectal cancer risk. An increased frequency only of the wild-type combined allele (rs2032582G/rs1045642C) was found in Caucasian patients (OR = 1.22, 95% CI: 1.03-1.44, P = 0.02).

CONCLUSION

There is some evidence to indicate an association between ABCB1 rs1045642T and colorectal cancer risk in Asians. Compared with the ABCB1 gene SNPs rs1045642, rs2032582 or rs3789243 alone, combined haplotypes of several SNPs might be a better marker to determine the genetic influence on the susceptibility to colorectal cancer among Caucasians.

MDR1 gene C3435T polymorphism and cancer risk: a meta-analysis of 34 case-control studies

BACKGROUND

P-glycoprotein, the product of the MDR1 gene, is a transmembrane active efflux pump for a variety of environmental toxins and xenobiotics. Epidemiological studies have evaluated the association between MDR1 C3435T polymorphism and cancer susceptibility. However, published data are still inconclusive.

METHODS

To derive a more precise assessment of this relevance, we performed a meta-analysis, up to September 2010, of 5,196 cases with different cancer types and 6,827 controls from 34 published case-control studies. Summary odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for MDR1 C3435T polymorphism and cancer were estimated using fixed- and random-effects models when appropriate.

RESULTS

The overall results suggested that the variant was associated with a moderately increased cancer risk in all comparison models tested (OR = 1.26, 95% CI: 1.06-1.50 for TT vs. CC; OR = 1.19, 95% CI: 1.04-1.37 for CT vs. CC; OR = 1.15, 95% CI: 1.01-1.32 for recessive model; OR = 1.21, 95% CI: 1.06-1.38 for domain model, and OR = 1.14, 95% CI: 1.04-1.26 for allele contrast). In the subgroup analysis by cancer types, significant associations were found in breast cancer (OR = 1.66, 95% CI: 1.24-2.21 for TT vs. CC; OR = 1.44, 95% CI: 1.14-1.82 for recessive model; OR = 1.41, 95% CI: 1.10-1.81 for domain model; and OR = 1.31, 95% CI: 1.13-1.52 for allele contrast) and renal cancer (OR = 1.99, 95% CI: 1.37-2.90 for TT vs. CC; OR = 1.74, 95% CI: 1.25-2.42 for domain model; OR = 1.43, 95% CI: 1.09-1.88 for recessive model; and OR = 1.40, 95% CI: 1.17-1.68 for allele contrast). However, no significant associations were found in colorectal cancer, gastric cancer, and acute lymphoblastic leukemia for all genetic models. In the ethnicity subgroup analysis, a significant association with cancer among Caucasians was found under the dominant model, homozygote comparison, CT versus CC comparison, and allele comparison.

CONCLUSIONS

In summary, this meta-analysis suggests that the MDR1 C3435T polymorphism is associated with cancer susceptibility, increasing the risk of breast and renal cancer.

A comprehensive investigation on common polymorphisms in the MDR1/ABCB1 transporter gene and susceptibility to colorectal cancer

ATP Binding Cassette B1 (ABCB1) is a transporter with a broad substrate specificity involved in the elimination of several carcinogens from the gut. Several polymorphic variants within the ABCB1 gene have been reported as modulators of ABCB1-mediated transport. We investigated the impact of ABCB1 genetic variants on colorectal cancer (CRC) risk. A hybrid tagging/functional approach was performed to select 28 single nucleotide polymorphisms (SNPs) that were genotyped in 1,321 Czech subjects, 699 CRC cases and 622 controls. In addition, six potentially functional SNPs were genotyped in 3,662 German subjects, 1,809 cases and 1,853 controls from the DACHS study. We found that three functional SNPs (rs1202168, rs1045642 and rs868755) were associated with CRC risk in the German population. Carriers of the rs1202168_T and rs868755_T alleles had an increased risk for CRC (P(trend) = 0.016 and 0.029, respectively), while individuals bearing the rs1045642_C allele showed a decreased risk of CRC (P(trend) = 0.022). We sought to replicate the most significant results in an independent case-control study of 3,803 subjects, 2,169 cases and 1,634 controls carried out in the North of Germany. None of the SNPs tested were significantly associated with CRC risk in the replication study. In conclusion, in this study of about 8,800 individuals we show that ABCB1 gene polymorphisms play at best a minor role in the susceptibility to CRC.

MDR1 C3435T polymorphism and cancer risk: a meta-analysis based on 39 case-control studies

Multidrug resistance 1 (MDR1) gene encodes the ATP-dependent cellular efflux pump P-glycoprotein (P-gp) which efflux of a variety of substances across the membrane. P-gp could serve a role in cancer etiology based on its physiological role of protecting cells from xenobiotics or metabolites. The C3435T (rs1045642) polymorphism of the MDR1 gene which could influence the P-gp expression and function have been implicated in the cancer risk. However, the results from the published studies on the association between this polymorphism and cancer risk are conflicting. To drive a more precise estimation of this association, we performed a meta-analysis of 39 case-control studies, including a total of 9,265 cancer cases and 13,502 controls. We used odds ratios (ORs) with their 95% confidence intervals (CIs) to assess the strength of the association. Overall, individuals with the MDR1 3435TT genotype were associated with an increased cancer risk than those with the CC (OR = 1.29, 95% CI: 1.10-1.51) or CT/CC (OR = 1.18, 95% CI: 1.04-1.34) genotypes, similar to the CT or CT/TT compared with the CC genotype. In the stratified analyses, the increased risks were more pounced among hematologic malignances (OR = 1.27, 95% CI: 1.10-1.46, P (heterogeneity) = 0.415), breast cancer (1.42, 1.04-1.94, 0.018), renal cancer (1.77, 1.28-2.46, 0.307), Caucasians (1.21, 1.07-1.38, 0.000) and population-based studies (1.20, 1.05-1.36, 0.000) in a dominant model. The results suggested that the MDR1 C3435T polymorphism may contribute to cancer risk.

APEX microarray panel for genotyping polymorphisms in cancer chemotherapy and estimation frequencies in a Slovak population

Aim: Many studies focus on monitoring response to chemotherapy, adverse effects and prediction of therapeutic effects, which depend on individual gene variability. The amount of various polymorphisms in genes involved in the folate cycle, and other metabolic pathways involved in the metabolism of chemotherapeutic drugs, are an essential topic of such studies. This work focuses on the design and establishment of a pharmacogenetically relevant panel, which could be applied to the rapid genotyping of patients treated with thiopurines, 5-fluorouracil, methotrexate, irinotecan and glucocorticoids. Materials & methods: A total of 97 variations in 36 genes associated with side effects of chemotherapeutic treatment were selected. Of these, 94 SNPs were genotyped by the arrayed primer extension (APEX; Asper Biotech Ltd) microarray method or direct sequencing. Variations of tandem repeats or gene deletions were genotyped by capillary electrophoresis and PCR detection. A total of 300 DNA samples from healthy volunteers were tested to estimate genotype frequencies for a Slovak population. All data were checked for Hardy–Weinberg equilibrium and genetic linkage between variations. Results: We designed an APEX microarray for genotyping pharmacologically relevant polymorphisms in patients undergoing chemotherapy. We estimated genotype frequencies for all 97 polymorphisms testing 300 individuals from the Slovak population, which may also serve as an estimate of central European frequencies. These data also allowed for the testing of genetic linkage between loci. Many of the determined genotype frequencies in this study were in similar ranges found in other European populations but four SNPs, rs11760837 (p = 0.018), rs1801265 (p = 0.0375), rs1801394 (p = 0.0066) and rs182455 (p = 0.0083), demonstrated stronger deviation. Conclusion: Genetic variability in genes involved in metabolic pathways of chemotherapeutic drugs, such as methotrexate, 5-fluorouracil, thiopurines or irinotecan, is responsible for individual therapy response and development of side effects. A comprehensive approach in genotyping of numerous variants is aimed to improve individual access to patients and the selection of appropriate drugs for treatment. The APEX microarray method is a valuable tool for fast, reliable and cost-effective genotyping of variants which can be used for the typing of known variants in patients prior to treatment as well as in studies searching for new genotype–phenotype associations. The opportunity of adding additional variants during the study makes the APEX microarray technology flexible and suitable for such trials.

Original submitted 4 October 2010; Revision submitted 23 November 2010.

Pharmacogenetics of ATP-binding cassette transporters and clinical implications

Drug resistance is a severe limitation of chemotherapy of various malignancies. In particular efflux transporters of the ATP-binding cassette family such as ABCB1 (P-glycoprotein), the ABCC (multidrug resistance-associated protein) family, and ABCG2 (breast cancer resistance protein) have been identified as major determinants of chemoresistance in tumor cells. Bioavailability depends not only on the activity of drug metabolizing enzymes but also to a major extent on the activity of drug transport across biomembranes. They are expressed in the apical membranes of many barrier tissues such as the intestine, liver, blood-brain barrier, kidney, placenta, testis, and in lymphocytes, thus contributing to plasma, liquor, but also intracellular drug disposition. Since expression and function exhibit a broad variability, it was hypothesized that hereditary variances in the genes of membrane transporters could explain at least in part interindividual differences of pharmacokinetics of a variety of anticancer drugs and many others contributing to the clinical outcome of certain leukemias and further malignancies.

Polymorphisms in the xenobiotic transporter Multidrug Resistance 1 (MDR1) and interaction with meat intake in relation to risk of colorectal cancer in a Danish prospective case-cohort study

Background

The xenobiotic transporters, Multidrug Resistance 1 (MDR1/ABCB1) and Breast Cancer Resistance Protein (BCRP/ABCG2) may restrict intestinal absorption of various carcinogens, including heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH). Cyclooxygenase-2 (COX-2) derived prostaglandins promote gastrointestinal carcinogenesis, affecting angiogenesis, apoptosis, and invasiveness.

The aim of this study was to investigate if polymorphisms in these genes were associated with risk of colorectal cancer (CRC), and to investigate possible interactions with lifestyle factors such as smoking, meat consumption, and NSAID use.

Methods

The following polymorphisms were analyzed; a synonymous MDR1 C3435T (rs1045642) in exon26, G-rs3789243-A in intron3, the functional BCRP C421A (rs2231142), the two COX-2 A-1195G (rs689466) and G-765C (rs20417) in the promoter region, and the COX-2 T8473C (rs5275) polymorphisms in the 3'-untranslated region. The polymorphisms were assessed together with lifestyle factors in a nested case-cohort study of 359 cases and a random cohort sample of 765 participants from the Danish prospective Diet, Cancer and Health study.

Results

Carriers of the variant allele of MDR1 intron 3 polymorphism were at 1.52-fold higher risk of CRC than homozygous wild type allele carriers (Incidence rate ratio (IRR) = 1.52, 95% Confidence Interval (CI): 1.12-2.06). Carriers of the variant allele of MDR1 C3435T exon 26 had a lower risk of CRC than homozygous C-allele carriers (IRR = 0.71 (CI:0.50-1.00)). There was interaction between these MDR1 polymorphisms and intake of red and processed meat in relation to CRC risk. Homozygous MDR1 C3435T C-allele carriers were at 8% increased risk pr 25 gram meat per day (CI: 1.00-1.16) whereas variant allele carriers were not at increased risk (p for interaction = 0.02). COX-2 and BCRP polymorphisms were not associated with CRC risk. There was interaction between NSAID use and MDR1 C3435T and COX-2 T8473C (p-values for interaction 0.001 and 0.04, respectively).

Conclusion

Two polymorphisms in MDR1 were associated with CRC risk and there was interaction between these polymorphisms and meat intake in relation to CRC risk. Our results suggest that MDR1 polymorphisms affect the relationship between meat and CRC risk.

ABCB1 gene polymorphisms and haplotype analysis in colorectal cancer

PURPOSE

The aim of this study was to determine the significance of three most common single-nucleotide polymorphisms (SNPs) of ABCB1 gene in the development of colorectal cancer and to estimate the influence of these SNPs to surviving patients' treatment combination adjuvant therapy 5-fluorouracil/leucovorin. Haplotype structure of ABCB1 was analysed, and degree of linkage disequilibrium (LD) between SNPs of ABCB1 was estimated.

MATERIALS AND METHODS

Tumour specimens of 95 patients with colorectal cancer and blood samples of 95 healthy cases were studied. Genotyping of ABCB1 gene was performed by automated sequencing or polymerase chain reaction-restriction fragment length polymorphism method. Comparison of frequencies of alleles/genotypes/haplotypes between the studied group (colorectal cancer samples) and the control group (blood samples) were analysed. These results were correlated with the surviving patients after treatment of adjuvant chemotherapy.

RESULTS

Significant differences in ABCB1 (1236C>T) (p = 0.00043) and ABCB1 (2677G>T/A) (p = 0.04) genotype distribution and T(1236) allele distribution (CT(1236) or TT(1236) vs CC(1236); p = 0.0499, OR = 0.55, Fi-Yule coefficient = 0.14) were found. A strong LD between ABCB1 (1236C>T) and ABCB1 (2677G>T/A) SNPs (D' = 0.621, r (2) = 0.318) was detected. All SNPs were located in one haplotype block. There were significant differences in haplotype distributions between colorectal cancer patients and healthy population (p = 0.03). Significant differences in survival probability of colorectal cancer patients' treatment chemotherapy according to allele of ABCB1 (3435C>T) was observed. Survival probability of patients with wild-type C(3435) allele were higher than among patients without this allele (p = 0.04572).

CONCLUSIONS

These results suggested that three studied SNPs of ABCB1 were located in one haplotype block. Differences in ABCB1 (1236C>T) and ABCB1 (2677G>T/A) genotypes and T(1236) allele distribution between investigated populations indicate significant impact of these SNPs on risk of development of colorectal cancer. Polymorphism ABCB1 (3435C>T) may be a prediction marker of cancer chemotherapy effectiveness. Differences in haplotype distributions between colorectal cancer patients and healthy population suggested that other potential SNPs, especially in regulatory region of ABCB1 gene, may influence P-glycoprotein expression and function.

The multidrug resistance 1 (MDR1) gene polymorphism G-rs3789243-A is not associated with disease susceptibility in Norwegian patients with colorectal adenoma and colorectal cancer; a case control study

Background

Smoking, dietary factors, and alcohol consumption are known life style factors contributing to gastrointestinal carcinogenesis. Genetic variations in carcinogen handling may affect cancer risk. The multidrug resistance 1(MDR1/ABCB1) gene encodes the transport protein P-glycoprotein (a phase III xenobiotic transporter). P-glycoprotein is present in the intestinal mucosal lining and restricts absorption of certain carcinogens, among these polycyclic aromatic hydrocarbons. Moreover, P-glycoprotein transports various endogenous substrates such as cytokines and chemokines involved in inflammation, and may thereby affect the risk of malignity. Hence, genetic variations that modify the function of P-glycoprotein may be associated with the risk of colorectal cancer (CRC). We have previously found an association between the MDR1 intron 3 G-rs3789243-A polymorphism and the risk of CRC in a Danish study population. The aim of this study was to investigate if this MDR1 polymorphism was associated with risk of colorectal adenoma (CA) and CRC in the Norwegian population.

Methods

Using a case-control design, the association between the MDR1 intron 3 G-rs3789243-A polymorphism and the risk of colorectal carcinomas and adenomas in the Norwegian population was assessed in 167 carcinomas, 990 adenomas, and 400 controls. Genotypes were determined by allelic discrimination. Odds ratio (OR) and 95 confidence interval (95% CI) were estimated by binary logistic regression.

Results

No association was found between the MDR1 polymorphism (G-rs3789243-A) and colorectal adenomas or cancer. Carriers of the variant allele of MDR1 intron 3 had odds ratios (95% CI) of 0.97 (0.72–1.29) for developing adenomas, and 0.70 (0.41–1.21) for colorectal cancer, respectively, compared to homozygous wild type carriers.

Conclusion

The MDR1 intron 3 (G-rs3789243-A) polymorphism was not associated with a risk of colorectal adenomas or carcinomas in the present Norwegian study group. Thus, this MDR1 polymorphism does not seem to play an important role in colorectal carcinogenesis in this population.

MDR1 C3435T polymorphism has no influence on developing Helicobacter pylori infection-related gastric cancer and peptic ulcer in Japanese

AIMS

P-glycoprotein, the gene product of multidrug-resistant transporter-1 (MDR1), confers multidrug resistance against antineoplastic agents but also affects the kinetic disposition of some drugs and carcinogens. MDR1 C3435T polymorphism influences the development of colon cancer and adult acute myeloid leukemia by the association with transporting carcinogen. The aim of this study was to clarify the association of MDR1 C3435T polymorphism with susceptibility to gastric cancer and peptic ulcers in patients with Japanese H. pylori infection.

MAIN METHODS

We assessed the MDR1 C3435T polymorphism in H. pylori-positive gastritis alone patients (n=150), gastric cancer (n=292), gastric ulcer (n=215), and duodenal ulcer (n=163) and H. pylori-negative subjects (n=168) as control by a PCR-based method.

KEY FINDINGS

No significant difference existed in frequencies of MDR1 C3435T polymorphisms between H. pylori-negative controls and H. pylori-positive gastritis alone patients. Moreover, MDR1-3435 T allele carriage didn't affect the risk of gastric cancer or peptic ulcer development. The age- and sex-adjusted odds ratios (ORs) of MDR1 3435 T allele carriers relative to the C/C genotype group for gastric cancer, gastric ulcer and duodenal ulcer risk were 0.96 (95%CI: 0.56-1.66), 1.16 (95%CI: 0.72-1.84) and 1.00 (95%CI: 0.61-1.62), respectively.

SIGNIFICANCE

In this preliminary data, the association with MDR1 C3435T polymorphism and risk for developing H. pylori-related gastric cancer and peptic ulcer in Japanese was low. P-glycoprotein might not be involved in the carcinogenesis of H. pylori-related gastric cancer.

ABC multidrug transporters: structure, function and role in chemoresistance

Three ATP-binding cassette (ABC)-superfamily multidrug efflux pumps are known to be responsible for chemoresistance; P-glycoprotein (ABCB1), MRP1 (ABCC1) and ABCG2 (BCRP). These transporters play an important role in normal physiology by protecting tissues from toxic xenobiotics and endogenous metabolites. Hydrophobic amphipathic compounds, including many clinically used drugs, interact with the substrate-binding pocket of these proteins via flexible hydrophobic and H-bonding interactions. These efflux pumps are expressed in many human tumors, where they likely contribute to resistance to chemotherapy treatment. However, the use of efflux-pump modulators in clinical cancer treatment has proved disappointing. Single nucleotide polymorphisms in ABC drug-efflux pumps may play a role in responses to drug therapy and disease susceptibility. The effect of various genotypes and haplotypes on the expression and function of these proteins is not yet clear, and their true impact remains controversial.