Association of MDR1 gene polymorphism (G2677T) with imatinib response in Egyptian chronic myeloid leukemia patients

An Improved Technique for Genotyping the ABCB1 Gene Variant of Exon 21

The Multidrug Resistance protein (ABCB1, MDR1) is involved in the transport of xenobiotics and antiretroviral drugs. Some variants of the ABCB1 gene are of clinical importance; among them, exon 12 (c.1236C>T, rs1128503), 21 (c.2677G>T/A, rs2032582), and 26 (c.3435C>T, rs1045642) have a high incidence in Caucasians. Several protocols have been used for genotyping the exon 21 variants, such as allele-specific PCR-RFLP using adapted primer to generate a digestion site for several enzymes and automatic sequencing to detect the SNVs, TaqMan Allele Discrimination assay and High-Resolution Melter analysis (HRMA). The aim was to describe a new approach to genotype the three variants c.2677G>T/A for the exon 21 doing only one PCR with the corresponding primers and the digestion of the PCR product with two restriction enzymes: BrsI to identify A allele and BseYI to differentiate between G or T. An improvement of this methodology was also described. The proposal technique here described is demonstrated to be very efficient, easy, fast, reproducible, and cost-effective.

Association of ABCB1, ABCG2 drug transporter polymorphisms and smoking with disease risk and cytogenetic response to imatinib in chronic myeloid leukemia patients

BACKGROUND

Despite acceptable results of imatinib in the treatment of chronic myeloid leukemia (CML), some patients fail to acquire a complete cytogenetic response (CCyR), which may be caused by polymorphisms in the pharmacogenetic genes. The study aimed to evaluate the association of two polymorphisms in the ABCB1 and ABCG2 genes with cytogenetic response to imatinib and the risk of CML development.

METHODS

We genotyped ABCB1 (c .2677G/T/A) and ABCG2 (c .421C/A) polymorphisms by PCR-RFLP, T-ARMS-PCR methods in 111 patients with CML and 102 sex- and age-matched healthy subjects. CCyR was determined by standard chromosome banding analysis (CBA).

RESULTS

Analysis of polymorphisms showed significant association of ABCG2 c.421CA genotype (p < 0.0001; OR = 0. 17), and ABCG2c.421A allele (p < 0.0001; OR = 0.31) with decreased risk of CML. Moreover, ABCB1c.2677GT- ABCG2c.421CC combined genotype (p = 0.017; OR = 4.20) was associated with increased risk of CML. Analysis of the joint effect of SNP-smoking combination showed that smoker subjects with the ABCB1c.2677GG/GT (p = 0.001; OR = 15.96, p = 0.001; OR = 8.13, respectively) or ABCG2c.421CC genotypes (p = 0.001; OR = 5.82) had the increased risk of CML, while the risk of the CML in non-smokers carrying the ABCG2c.421CA (p < 0.0001; OR = 0. 18) genotype was strongly decreased compared with reference group. Regarding drug response, ABCG2c.421 CC/CA genotypes in the smoker patients were associated with an increased risk of resistance to imatinib (p < 0.0001; OR = 7.02, p = 0.018; OR = 4.67, respectively).

CONCLUSION

Our results suggest the impact of ABCG2c .421C/A polymorphism on CML development, and smoking may have a synergistic role in the risk of CML and resistance to imatinib.

Impact of ABCB1 Gene (C3435T/A2677G) Polymorphic Sequence Variations on the Outcome of Patients with Chronic Myeloid Leukemia and Acute Lymphoblastic Leukemia in Kashmiri Population: A Case-Control Study

Inherited polymorphic sequence variations in drug transport genes like ABCB1 impact a portion of patients with hematologic malignancies that show intrinsic or acquire resistance to treatment. Keeping in view inter-individual sensitivities for such drugs, we through this case-control study tested whether ABCB1 C3435T and G2677T polymorphisms have any influence on the risk and treatment response in patients with chronic myeloid leukemia (CML) and B-acute lymphoblastic leukemia (B-ALL). Genotyping for ABCB1 polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism in 100 CML and 80 B-ALL patients along with 100 age and gender matched healthy controls. ABCB1 C3435T and G2677T polymorphism showed no association with CML. Genotype distribution revealed significant higher frequency of TT genotype for both SNPs in B-ALL cases and associated with increased B-ALL risk (OR 2.5, p = 0.04 for 3435TT; OR 2.4, p = 0.04 for 2677TT). There was no significant difference in genotype frequency of 3435C > T and 2677G > T among resistant and responsive groups for the two leukemia types. Kaplan-Meier survival plots revealed significantly lower event free survival in CML and B-ALL patients that were carriers of 3435TT genotype (p < 0.05). Multivariate analysis considered 3435TT genotype as independent risk factor for imatinib resistance in CML cases (HR 6.24, p = 0.002) and increased relapse risk in B-ALL patients (HR 4.51, p = 0.03). The current study provides preliminary evidence of a significant association between variant TT genotype and increased B-ALL risk. Also, results suggest that ABCB1 3435TT genotype increases imatinib resistance in CML and influence therapeutic outcome in B-ALL.

MDR1 gene polymorphisms and imatinib response in chronic myeloid leukemia: A meta-analysis

BACKGROUND

Our study aimed to investigate the association between multidrug resistance (MDR1) C1236T, C3435T and G2677T/A polymorphisms and the response to imatinib (IM) in chronic myeloid leukemia (CML).

MATERIALS AND METHODS

An electronic databases in PubMed, Embase, Web of Knowledge, Scopus and Cochrane were searched using combinations of keywords relating to MDR1 polymorphisms and the response to IM in CML. Studies retrieved from database searches were screened using strict inclusion and exclusion criteria.

RESULTS

In total, 37 studies were initially identified, and 17 studies, involving 4494 CML patients, were eventually included in this meta-analysis.Results of our study revealed significant association between MDR1 G2677T/A and C3435T polymorphisms and response to IM in Caucasian population under recessive model (T or A vs G; OR = 1.43,95%CI [1;06-1.93]; T vs C;OR = 1.13; 95%IC [0.79; 1.63]), dominant (T or A vs G; OR = 0.94; 95%CI [0.74-1.21]; T vs C; OR = 1.49; 95%CI [1.02-2.17]) and heterozygous models (T or A vs G; OR = 0.83; 95%CI [0.64; 1.09]; T vs C; OR = 1.52; 95%CI [1.01-2.28]); respectively. However, never significative association was found between IM response and the MDR1 C1236T polymorphism (OR = 1.25; 95%CI [0.46; 3.33]).

CONCLUSION

The MDR1 G2677T/A and C3435T polymorphisms might be a risk factor for resistance to IM in Caucasian CML patients.

Association of the Trough, Peak/Trough Ratio of Imatinib, Pyridine-N-Oxide Imatinib and ABCG2 SNPs 34 G>A and SLCO1B3 334 T>G With Imatinib Response in Egyptian Chronic Myeloid Leukemia Patients

Imatinib mesylate (IM) is highly efficacious in the treatment of chronic myeloid leukemia (CML). Therapeutic drug monitoring and pharmacogenetic screening are affirmed for better management of IM therapy. The goal of this study was to gain a greater mechanistic understanding of the factors controlling variability in IM level and its relation to the response. One hundred and two patients with CML at chronic phase were recruited in this study. Blood samples were withdrawn at least 30 days after drug administration, and trough and peak concentrations of imatinib, N-des-methyl imatinib, and pyridine-N-oxide imatinib were determined by HPLC/MS/MS. Genetic polymorphism of the genes ABCG2 SNPs 34 G>A and 421C >A; ABCB1 SNPs 2677 G>A/T, 1236 C>T, 3435 C>T; SLCO1B3 SNPs 334 T>G and CYP3A5 were studied using PCR-RFLP technique. Our study presented significant higher trough IM (1,281 ± 578 ng/ml), lower Peak/Trough ratio, clearance (Cl), and elimination rate constant, k_e, among patients who achieved favorable responses (N = 64) than those for patients who suffered unfavorable response (N = 37). The P/T ratio was the only significant independent factor affecting response, as the P/T ratio increased by one, the risk of unfavorable response increased by more than double as compared to favorable response with 95% CI (1.28-3.92, P = 00.005). Moreover, like the results of IM, the trough concentration of Pyridine-N-oxide imatinib was significantly higher (P = 0.01) and its P/T ratio was significantly lower (P = 0.008) in patients achieved favorable response than those without. The wild GG genotype of the ABCG2.34 G>A gene was associated with favorable response (P = 0.01), lower Cl, K_e and high plasma IM trough level than both (AA+GA) genotypes. ABCG2.421C >A (CC) genotype had a significantly higher plasma peak of IM, N-des-methyl imatinib and higher C_ss. The GG and TG alleles of the SLCO1B3.334 T>G gene were significantly correlated to favorable response, while the wild allele TT was linked to unfavorable response (P = 0.03). In conclusion, the trough and P/ T ratio for both IM and Pyridine-N-oxide imatinib, in addition to Polymorphism of ABCG2 SNPs 34 G>A and SLCO1B3.334 T>G gene, is a good predictor for response of IM in CML Egyptian patients.

A review of clinical pharmacogenetics Studies in African populations

Effective interventions and treatments for complex diseases have been implemented globally, however, coverage in Africa has been comparatively lower due to lack of capacity, clinical applicability and knowledge on the genetic contribution to disease and treatment. Currently, there is a scarcity of genetic data on African populations, which have enormous genetic diversity. Pharmacogenomics studies have the potential to revolutionise treatment of diseases, therefore, African populations are likely to benefit from these approaches to identify likely responders, reduce adverse side effects and optimise drug dosing. This review discusses clinical pharmacogenetics studies conducted in African populations, focusing on studies that examined drug response in complex diseases relevant to healthcare. Several pharmacogenetics associations have emerged from African studies, as have gaps in knowledge.

Clinical Implication of MicroRNAs in Molecular Pathology: An Update for 2018

MicroRNAs (miRNAs) are poised to provide diagnostic, prognostic, and therapeutic targets for several diseases including malignancies for precision medicine applications. The miRNAs have immense potential in the clinical arena because they can be detected in the blood, serum, tissues (fresh and formalin-fixed paraffin-embedded), and fine-needle aspirate specimens. The most attractive feature of miRNA-based therapy is that a single miRNA could be useful for targeting multiple genes that are deregulated in cancers, which can be further investigated through systems biology and network analysis that may provide cancer-specific personalized therapy.

Association of C3435T, C1236T and C4125A Polymorphisms of the MDR-1 Gene in Egyptian Children with Acute Lymphoblastic Leukaemia

Background:

P-glycoprotein (P-gp), a membrane transporter encoded by the multidrug resistance-1 (MDR1) gene, influences pharmacokinetics and metabolism of anticancer drugs and contributes to multidrug resistance phenotype in acute lymphoblastic leukemia (ALL). Genetic variation ofMDR1 in ALL patients is increasingly recognized as a factor influencing response to treatment.

Aim:

To investigate the possible role of MDR-1 gene polymorphisms (C3435T, C1236T and C4125A) as risk factors for the development and clinical outcome of ALL in Egyptian children.

Materials and Methods:

Genotyping of MDR-1 C3435T, C1236T and C4125A single nucleotide polymorphisms (SNPs) was accomplished using a polymerase chain reaction–restriction fragment length polymorphism (RFLP-PCR) assay with 120 childhood ALL patients and 100 healthy controls.

Results:

Homozygous T with the C3435T SNP showed a protective effect as compared to homozygous C (OR=0.748) while heterozygous CT correlated with a poor outcome (high risk, drug unresponsiveness, relapse and high percentage of death). Additionally, the T allele of the C1236T SNP showed a significant relation with ALL risk (OR=1.6). However, there were no significant differences in the genotype and allele frequencies of MDR-1 SNPs between patients and controls. Only one genotype (CC) and one allele of MDR-1 (C4125A) were seen. Neither CA/AA genotypes nor A alleles were present in ALL patients and normal controls. TC was the predominant haplotype in both groups, while CT proved to be minor. The cumulative incidence of relapse was higher with the CC genotype of C1236T as compared with TT.

Conclusion:

From our preliminary data, the CT genotype of C3435T is associated with a poor ALL outcome while the CC genotype of C1236T is related with an increased incidence of relapse. Although our results provide assistance for oncologist choice of individual therapeutic strategy taking the patient genetic repertoire into consideration, further investigations with larger sample size should be conducted to validate our results.

Association between MDR1 gene polymorphism and clinical course of pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease with a complex pathogenesis. The polymorphism of the gene of multidrug resistance-1 (MDR1) has been associated with many diseases including PAH.

Objective. In this study we aimed to investigate the relevance of the MDR1 polymorphism to pediatric PAH clinical course.

Methods. A total of 40 pediatric patients with PAH (secondary to congenital heart defects or idiopathic) and 40 control subjects were enrolled. Patients with PAH were divided into 2 groups, according to their evolution: 28 patients who remained clinically stable at 12-months (non-worsening group) and 12 patients who presented clinical worsening at 12-months (worsening group). Genomic DNA was genotyped for MDR1 gene polymorphisms as follows: C1236T, G2677T and C3435T.

Results. There were no significant differences between PAH children groups (clinical worsening and non-worsening) nor between PAH children and controls in terms of frequency distribution of the three studied genotypes or alleles.

Conclusions. The MDR1 polymorphism could not be correlated with the clinical evolution of pediatric PAH patients in our study.

Towards Comprehension of the ABCB1/P-Glycoprotein Role in Chronic Myeloid Leukemia

Abstract: The introduction of imatinib (IM), a BCR-ABL1 tyrosine kinase inhibitor (TKI), has represented a significant advance in the first-line treatment of chronic myeloid leukemia (CML). However, approximately 30% of patients need to discontinue IM due to resistance or intolerance to this drug. Both resistance and intolerance have also been observed in treatment with the second-generation TKIs-dasatinib, nilotinib, and bosutinib-and the third-generation TKI-ponatinib. The mechanisms of resistance to TKIs may be BCR-ABL1-dependent and/or BCR-ABL1-independent. Although the role of efflux pump P-glycoprotein (Pgp), codified by the ABCB1 gene, is unquestionable in drug resistance of many neoplasms, a longstanding question exists about whether Pgp has a firm implication in TKI resistance in the clinical scenario. The goal of this review is to offer an overview of ABCB1/Pgp expression/activity/polymorphisms in CML. Understanding how interactions, associations, or cooperation between Pgp and other molecules-such as inhibitor apoptosis proteins, microRNAs, or microvesicles-impact IM resistance risk may be critical in evaluating the response to TKIs in CML patients. In addition, new non-TKI compounds may be necessary in order to overcome the resistance mediated by Pgp in CML.

ABCB1 genetic variants in leukemias: current insights into treatment outcomes

Despite improvements in treatment of different types of leukemia, not all patients respond optimally for a particular treatment. Some treatments will work better for some, while being harmful or ineffective for others. This is due to genetic variation in the form of single-nucleotide polymorphisms (SNPs) that affect gene expression or function and cause inherited interindividual differences in the metabolism and disposition of drugs. Drug transporters are one of the determinants governing the pharmacokinetic profile of chemotherapeutic drugs. The ABCB1 transporter gene transports a wide range of drugs, including drugs used in leukemia treatment. Polymorphisms in the ABCB1 gene do affect intrinsic resistance and pharmacokinetics of several drugs used in leukemia treatment protocols and thereby affect the efficacy of treatment and event-free survival. This review focuses on the impact of three commonly occurring SNPs (1236C>T, 2677G>T/A, and 3435C>T) of ABCB1 on treatment response of various types of leukemia. From the literature available, some of the genotypes and haplotypes of these SNPs have been found to be potential determinants of interindividual variability in drug disposition and pharmacologic response in different types of leukemia. However, due to inconsistencies in the results observed across the studies, additional studies, considering novel genomic methodologies, comprehensive definition of clinical phenotypes, adequate sample size, and uniformity in all the confounding factors, are warranted.

Influence of MDR1 and CYP3A5 genetic polymorphisms on trough levels and therapeutic response of imatinib in newly diagnosed patients with chronic myeloid leukemia

Polymorphisms in genes coding for imatinib transporters and metabolizing enzymes may affect imatinib pharmacokinetics and clinical response. Aim of this study was to assess the influence of polymorphisms in MDR1 and CYP3A5 genes on imatinib trough levels, cytogenetic and molecular response in patients with CML. Newly diagnosed patients with chronic-phase CML started on imatinib therapy were enrolled and followed up prospectively for 24 months. The following single nucleotide polymorphisms were genotyped; C1236T, C3435T, G2677T/A in MDR1 gene and A6986G in CYP3A5 gene. Genotyping was done using PCR-RFLP method and validated by direct gene sequencing. Trough levels of imatinib were measured using LC-MS/MS. Cytogenetic response was assessed by conventional bone-marrow cytogenetics. Molecular response was assessed by qRTPCR using international scale. A total of 173 patients were included, out of which 71 patients were imatinib responders, while 102 were non-responders. Marked inter-individual variability in trough levels of imatinib was seen. Patients with GG genotype for CYP3A5-A6986G (P=0.016) and TT genotype for MDR1-C3435T (P=0.013) polymorphisms had significantly higher trough levels of imatinib. Patients with AA genotype for CYP3A5-A6986G [RR=1.448, 95% CI (1.126, 1.860), P=0.029] and CC genotype for MDR1-C1236T [RR=1.397, 95% CI (1.066, 1.831), P=0.06] &MDR1-C3435T [RR=1.508, 95% CI (1.186, 1.917), P=0.018] polymorphisms were at high risk for failure of imatinib therapy. Patients with CGC haplotype for MDR1 polymorphisms had significantly lower imatinib trough levels and were at a higher risk of imatinib failure [RR=1.547, 95% CI (1.324, 1.808), P<0.001]. GG vs. non-GG genotype for CYP3A5-A6986G [adjusted OR: 0.246; 95% CI (0.116, 0.519); P<0.001] and TT vs. non-TT genotype for MDR1-C1236T [adjusted OR: 0.270; 95% CI (0.110, 0.659); P=0.004] &MDR1-C3435T [adjusted OR: 0.289; 95% CI (0.135, 0.615); P=0.001] polymorphisms were independent factors predicting imatinib response in multivariate analysis. To conclude, MDR1 and CYP3A5 genetic polymorphisms significantly influence plasma trough levels and therapeutic response of imatinib in patients with CML. Genotyping of these polymorphisms could be of value to individualize the therapy and optimize the clinical outcomes.

Trough concentration and ABCG2 polymorphism are better to predict imatinib response in chronic myeloid leukemia: a meta-analysis

AIM

The present study aimed to conduct a series of meta-analyses to investigate the influence of imatinib trough concentration (C₀), as well as ABCB1 and ABCG2 polymorphisms, on the clinical response in patients with chronic myeloid leukemia (CML).

METHODS

A literature search was conducted using the PubMed and Cochrane electronic databases to locate relevant papers from 2003 onward. Then, an initial meta-analysis of 14 studies involving 2184 patients was conducted to understand the effect of imatinib mesylate (IM) C₀ on clinical outcome in CML patients. Subsequently, a series of meta-analyses were performed, including up to 23 studies with 2577 patients, on the effect of genetic polymorphisms of ABCB1 and ABCG2 on the clinical response to IM.

RESULTS

Meta-analysis revealed that patients who achieved a major molecular response (MMR) have a significantly higher IM C₀ than those who failed to achieve an MMR. We also found that the patients who achieved a complete cytogenic response (CCyR) have a significantly higher IM C₀ than those who did not achieve a CCyR. However, no significant difference in IM C₀ was found between the complete molecular response and non-complete molecular response groups. Additional analysis showed that ABCG2 421 variant A allele was significantly associated with a higher rate of MMR and overall response, especially in Asian patients. Meta-analysis did not reveal a correlation between ABCB1 C3435T and C1236T polymorphisms with any clinical response to IM. However, the G2677T/A polymorphism could play a role in IM response in the recessive model.

CONCLUSION

This meta-analysis demonstrates that there was a significant correlation between the IM trough concentration and clinical responses, especially MMR and CCyR, in CML patients. Furthermore, we found that the probability of successful treatment was correlated with the ABCG2 C421A polymorphism, at least within the Asian population. We failed to determine an association between ABCB1 polymorphisms and IM response, although the G2677T/A polymorphism might be involved. However, further large-scale investigations using more sensitive genotyping methods would be required to confirm this.

Impact of Membrane Drug Transporters on Resistance to Small-Molecule Tyrosine Kinase Inhibitors

Small-molecule inhibitors of tyrosine kinases (TKIs) are the mainstay of treatment for many malignancies and represent novel treatment options for other diseases such as idiopathic pulmonary fibrosis. Twenty-five TKIs are currently FDA-approved and >130 are being evaluated in clinical trials. Increasing evidence suggests that drug exposure of TKIs may significantly contribute to drug resistance, independently from somatic variation of TKI target genes. Membrane transport proteins may limit the amount of TKI reaching the target cells. This review highlights current knowledge on the basic and clinical pharmacology of membrane transporters involved in TKI disposition and their contribution to drug efficacy and adverse drug effects. In addition to non-genetic and epigenetic factors, genetic variants, particularly rare ones, in transporter genes are promising novel factors to explain interindividual variability in the response to TKI therapy.

Regulatory network analysis of microRNAs and genes in imatinib-resistant chronic myeloid leukemia

Targeted therapy in the form of selective breakpoint cluster region-abelson (BCR/ABL) tyrosine kinase inhibitor (imatinib mesylate) has successfully been introduced in the treatment of the chronic myeloid leukemia (CML). However, acquired resistance against imatinib mesylate (IM) has been reported in nearly half of patients and has been recognized as major issue in clinical practice. Multiple resistance genes and microRNAs (miRNAs) are thought to be involved in the IM resistance process. These resistance genes and miRNAs tend to interact with each other through a regulatory network. Therefore, it is crucial to study the impact of these interactions in the IM resistance process. The present study focused on miRNA and gene network analysis in order to elucidate the role of interacting elements and to understand their functional contribution in therapeutic failure. Unlike previous studies which were centered only on genes or miRNAs, the prime focus of the present study was on relationships. To this end, three regulatory networks including differentially expressed, related, and global networks were constructed and analyzed in search of similarities and differences. Regulatory associations between miRNAs and their target genes, transcription factors and miRNAs, as well as miRNAs and their host genes were also macroscopically investigated. Certain key pathways in the three networks, especially in the differentially expressed network, were featured. The differentially expressed network emerged as a fault map of IM-resistant CML. Theoretically, the IM resistance process could be prevented by correcting the included errors. The present network-based approach to study resistance miRNAs and genes might help in understanding the molecular mechanisms of IM resistance in CML as well as in the improvement of CML therapy.

Impact of Genetic Polymorphisms of ABCB1 (MDR1, P-Glycoprotein) on Drug Disposition and Potential Clinical Implications: Update of the Literature

ATP-binding cassette transporter B1 (ABCB1; P-glycoprotein; multidrug resistance protein 1) is an adenosine triphosphate (ATP)-dependent efflux transporter located in the plasma membrane of many different cell types. Numerous structurally unrelated compounds, including drugs and environmental toxins, have been identified as substrates. ABCB1 limits the absorption of xenobiotics from the gut lumen, protects sensitive tissues (e.g. the brain, fetus and testes) from xenobiotics and is involved in biliary and renal secretion of its substrates. In recent years, a large number of polymorphisms of the ABCB1 [ATP-binding cassette, sub-family B (MDR/TAP), member 1] gene have been described. The variants 1236C>T (rs1128503, p.G412G), 2677G>T/A (rs2032582, p.A893S/T) and 3435C>T (rs1045642, p.I1145I) occur at high allele frequencies and create a common haplotype; therefore, they have been most widely studied. This review provides an overview of clinical studies published between 2002 and March 2015. In summary, the effect of ABCB1 variation on P-glycoprotein expression (messenger RNA and protein expression) and/or activity in various tissues (e.g. the liver, gut and heart) appears to be small. Although polymorphisms and haplotypes of ABCB1 have been associated with alterations in drug disposition and drug response, including adverse events with various ABCB1 substrates in different ethnic populations, the results have been majorly conflicting, with limited clinical relevance. Future research activities are warranted, considering a deep-sequencing approach, as well as well-designed clinical studies with appropriate sample sizes to elucidate the impact of rare ABCB1 variants and their potential consequences for effect sizes.

Multidrug resistance gene 1 C1236T polymorphism and susceptibility to leukemia: A meta-analysis

Several studies have investigated the association between multidrug resistance gene (MDR1) C1236T polymorphism and leukemia risk, however, these published studies have yielded conflicting results. Thus, the present study carried out a meta-analysis to provide a more precise estimate of the effect of this polymorphism on the susceptibility to leukemia. The published case-control studies regarding the association between MDR1 C1236T polymorphism and leukemia risk were included following a computerized search of PubMed, Elsevier, The Cochrane Library, China National Knowledge Infrastructure and Wanfang Database. Either fixed- or random-effects models were applied to calculate the combined odds ratios (ORs) and 95% confidence intervals (CIs) by RevMan 5.2 software. Seven studies, including 846 cases and 1,523 controls, were included in the present meta-analysis. The results indicated that there was no significant association between the MDR1 C1236T polymorphism and leukemia risk in overall comparisons in all four genetic models (CT vs. CC: OR, 1.31, 95% CI, 0.89-1.91, P=0.17; TT vs. CC: OR, 2.16, 95% CI, 0.99-4.70, P=0.05; TT vs. CC+CT: OR, 1.72, 95% CI, 0.91-3.25, P=0.09; and CT+TT vs. CC: OR, 1.57, 95% CI, 0.96-2.56, P=0.07). In the subgroup analysis according to specific ethnicity, age and the type of leukemia, a significant association was found in adult leukemia (CT+TT vs. CC: OR, 2.77, 95% CI, 1.05-7.31, P=0.04) and chronic myeloid leukemia (CT vs. CC: OR, 1.71, 95% CI, 1.05-2.80, P=0.03). No significant publication bias was detected by funnel plot. Therefore, the meta-analysis indicated that the MDR1 C1236T polymorphism may contribute to the susceptibility to adult leukemia and chronic myeloid leukemia. Furthe well-designed studies based on larger sample sizes are required to validate these findings.

Correlations of ezrin expression with pathological characteristics and prognosis of osteosarcoma: a meta-analysis

We conducted a meta-analysis to comprehensively evaluate the correlations of ezrin expression with pathological characteristics and the prognosis of osteosarcoma. The MEDLINE (1966–2013), the Cochrane Library Database, EMBASE, CINAHL, Web of Science (1945–2013), and the Chinese Biomedical Database were searched without language restrictions. Meta-analyses conducted using STATA software were calculated. Ten studies met the inclusion criteria, including 459 patients with osteosarcoma. Meta-analysis results illustrated that ezrin expression may be closely associated with the recurrence of osteosarcoma or metastasis in osteosarcoma. Our findings also demonstrated that patients with grade III-IV osteosarcoma showed a higher frequency of ezrin expression than those with histological grade I-II osteosarcoma. Furthermore, we found that patients with positive expression of ezrin exhibited a shorter overall survival than those with negative ezrin expression. The results also indicated that positive ezrin expression was strongly correlated with poorer metastasis-free survival. Nevertheless, no significant relationships were observed between ezrin expression and clinical variables (age and gender). In the current meta-analysis, our results illustrated significant relationships of ezrin expression with pathological characteristics and prognosis of osteosarcoma. Thus, ezrin expression could be a promising marker in predicting the clinical outcome of patients with osteosarcoma.

ABCB1 polymorphisms predict imatinib response in chronic myeloid leukemia patients: a systematic review and meta-analysis

Imatinib mesylate, a competitive tyrosine kinase inhibitor, is considered the first-line therapy drug for Ph+ chronic myeloid leukemia (CML). Three single-nucleotide polymorphisms (SNPs) in the ATP-binding cassette, subfamily B (MDR/TAP), member 1 gene (ABCB1/MDR1), c.1236C>T, c.2677G>T/A and c.3435C>T, have been shown to affect cellular transport/metabolism of imatinib. The associations between these SNPs and imatinib response in CML patients have been widely evaluated, but the results were inconsistent. To derive a conclusive assessment of the associations, we performed a meta-analysis by combining data from a total of 12 reports including 1826 patients. The results showed that the 2677G allele or 3435T allele predicted a worse response to imatinib in CML patients, whereas 1236CC genotype was associated with better response in CML patients from Asian region. In conclusion, this meta-analysis suggests that c.1236C>T, c.2677G>T/A and c.3435C>T can be served as predictive markers for the therapeutical use of imatinib in CML patients.

Association of MDR1 G2677T polymorphism and leukemia risk: evidence from a meta-analysis

In the light of the relationship between the MDR1 G2677T polymorphism and the risk of leukemia remains inclusive or controversial. For better understanding of the effect of MDR1 G2677T polymorphism on leukemia risk, we performed a meta-analysis. Eligible studies were identified through a search of electronic databases such as PubMed, Excerpta Medica Database (Embase), Cochrane Library, and Chinese Biomedical Literature Database (CBM). The association between the MDR1 G2677T polymorphism and leukemia risk was conducted by odds ratios (ORs) and 95% confidence intervals (95% CI). A total of seven publications including eight studies with 1,229 cases and 1,097 controls were included in the meta-analysis. There was no association between MDR1 G2677T polymorphism and leukemia risk in all of five models in overall populations (T vs. G: OR = 1.00, 95% CI = 0.88-1.12, P = 0.914; TT vs. GG: OR = 0.97, 95% CI = 0.75-1.26, P = 0.812; TG vs. GG: OR = 1.00, 95% CI = 0.92-1.08, P = 0.939; TT vs.

TG/GG

OR = 0.98, 95% CI = 0.67-1.43, P = 0.906; TT/TG vs. GG: OR = 1.00, 95% CI = 0.95-1.06, P = 0.994). However, the significant association was found in others (Table 2) under the homozygote model (TT vs. GG: OR = 0.68, 95% CI = 0.48-0.94, P = 0.020) and recessive model (TT vs.

TG/GG

OR = 0.63, 95% CI = 0.43-0.92, P = 0.016). In the subgroup analysis, according to the type of leukemia, significant association was found between MDR1 G2677T polymorphism and myeloid leukemia but not lymphoblastic leukemia (TT vs. GG: OR = 0.66, 95% CI = 0.46-0.95, P = 0.026; TT vs.

TG/GG

OR = 0.56, 95% CI = 0.38-0.84, P = 0.005). The results suggested that there was no association between MDR1 G2677T polymorphism and leukemia risk in overall populations, but significant association was found in others populations (Asians and Africans), and myeloid leukemia indicated that G2677T polymorphism might be a protective factor in the susceptibility of myeloid leukemia and in Asians and Africans.