Association of ABCB1 polymorphisms with prognostic outcomes of anthracycline and cytarabine in Chinese patients with acute myeloid leukemia

Computational Analysis of MDR1 Variants Predicts Effect on Cancer Cells via their Effect on mRNA Folding

The P-glycoprotein efflux pump, encoded by the MDR1 gene, is an ATP-driven transporter capable of expelling a diverse array of compounds from cells. Overexpression of this protein is implicated in the multi-drug resistant phenotype observed in various cancers. Numerous studies have attempted to decipher the impact of genetic variants within MDR1 on P-glycoprotein expression, functional activity, and clinical outcomes in cancer patients. Among these, three specific single nucleotide polymorphisms-T1236C, T2677G, and T3435C - have been the focus of extensive research efforts, primarily through in vitro cell line models and clinical cohort analyses. However, the findings from these studies have been remarkably contradictory. In this study, we employ a computational, data-driven approach to systematically evaluate the effects of these three variants on principal stages of the gene expression process. Leveraging current knowledge of gene regulatory mechanisms, we elucidate potential mechanisms by which these variants could modulate P-glycoprotein levels and function. Our findings suggest that all three variants significantly change the mRNA folding in their vicinity. This change in mRNA structure is predicted to increase local translation elongation rates, but not to change the protein expression. Nonetheless, the increased translation rate near T3435C is predicted to affect the protein's co-translational folding trajectory in the region of the second ATP binding domain. This potentially impacts P-glycoprotein conformation and function. Our study demonstrates the value of computational approaches in elucidating the functional consequences of genetic variants. This framework provides new insights into the molecular mechanisms of MDR1 variants and their potential impact on cancer prognosis and treatment resistance. Furthermore, we introduce an approach which can be systematically applied to identify mutations potentially affecting mRNA folding in pathology. We demonstrate the utility of this approach on both ClinVar and TCGA and identify hundreds of disease related variants that modify mRNA folding at essential positions.

Can pharmacogenetics impact the therapeutic effect of cytarabine and anthracyclines in adult acute myeloid leukaemia patients?: A Serbian experience

Background

Cytarabine-anthracycline-based induction chemotherapy remains the standard of care for remission induction among patients with newly diagnosed acute myeloid leukaemia (AML). There are remarkable differences in therapy response among AML patients. This fact could be partly explained by the patients' genetic variability related to the metabolic paths of cytarabine and anthracyclines. This study aims to evaluate the effect of variants in pharmacogenes SLC29A1, DCK, ABCB1, GSTM1, and GSTT1, as well as laboratory and AML-related parameters on clinical outcomes in adult AML patients.

Methods

A total of 100 AML patients were included in the study. Pharmacogenetic variants SLC29A1 rs9394992, DCK rs12648166, ABCB1 rs2032582, and GSTM1 and GSTT1 gene deletions were detected by methodology based on PCR, fragment analysis and direct sequencing. The methods of descriptive and analytic statistics were used. Survival analysis was done using the Kaplan-Meier method using the Log-Rank test.

Results

This is the first study of adult AML pharmacogenetics in the Serbian population. Clinical outcomes in our cohort of AML patients were not impacted by analysed variants in SLC29A1, DCK, ABCB1 and GSTT1, and GSTM1 genes, independently or in combinations. Achievement of complete remission was identified as an independent prognostic indicator of clinical outcome.

Conclusions

The population-specific genomic profile has to be considered in pharmacogenetics. Since the data on AML pharmacogenetics in European populations is limited, our results contribute to knowledge in this field and strongly indicate that a high-throughput approach must be applied to find particular pharmacogenetic markers of AML in the European population.

ABC transporters are predictors of treatment failure in acute myeloid leukaemia

INTRODUCTION

To date, no chemoresistance predictors are included in acute myeloid leukaemia (AML) prognostic scoring systems to distinguish responding and refractory AML patients prior to chemotherapy. ABC transporters have been described as altering AML chemosensitivity; however, a relevant study investigating their role at various molecular levels was lacking.

METHODS

Gene expression, genetic variants, methylation and activity of ABCA2, ABCA5, ABCB1, ABCB6, ABCC1, ABCC3 and ABCG2 were analysed in AML blasts and healthy myeloblasts. Differences between responding and refractory AML in a cohort of 113 patients treated with 3 + 7 induction therapy were explored.

RESULTS

ABCC3 variant rs2301837 (p = 0.049), ABCG2 variant rs11736552 (p = 0.044), higher ABCA2 (p = 0.021), ABCC1 (p = 0.017), and ABCG2 expression (p = 0.023) and a higher number of concurrently overexpressed transporters (p = 0.002) were predictive of treatment failure by multivariate analysis. Expression of ABCA5 (p = 0.003), ABCB6 (p = 0.001) and ABCC3 (p < 0.0001) increased significantly after chemotherapy. Higher ABCG2 promoter methylation correlated with lower ABCG2 expression (p = 0.0001). ABCC1 was identified as the most active transporter in AML blasts by functional analysis.

CONCLUSIONS

ABC transporters, especially ABCC1 seem to contribute substantially to AML chemoresistance. A detailed understanding of chemoresistance mechanisms and the clinical implications of chemosensitivity predictors may lead to alternative therapeutic approaches for AML patients with unveiled chemoresistance signatures.

Role of Drug Transporters in Elucidating Inter-Individual Variability in Pediatric Chemotherapy-Related Toxicities and Response

Pediatric cancer treatment has evolved significantly in recent decades. The implementation of risk stratification strategies and the selection of evidence-based chemotherapy combinations have improved survival outcomes. However, there is large interindividual variability in terms of chemotherapy-related toxicities and, sometimes, the response among this population. This variability is partly attributed to the functional variability of drug-metabolizing enzymes (DME) and drug transporters (DTS) involved in the process of absorption, distribution, metabolism and excretion (ADME). The DTS, being ubiquitous, affects drug disposition across membranes and has relevance in determining chemotherapy response in pediatric cancer patients. Among the factors affecting DTS function, ontogeny or maturation is important in the pediatric population. In this narrative review, we describe the role of drug uptake/efflux transporters in defining pediatric chemotherapy-treatment-related toxicities and responses. Developmental differences in DTS and the consequent implications are also briefly discussed for the most commonly used chemotherapeutic drugs in the pediatric population.

Systematic Review of Pharmacogenetics of ABC and SLC Transporter Genes in Acute Myeloid Leukemia

Antineoplastic uptake by blast cells in acute myeloid leukemia (AML) could be influenced by influx and efflux transporters, especially solute carriers (SLCs) and ATP-binding cassette family (ABC) pumps. Genetic variability in SLC and ABC could produce interindividual differences in clinical outcomes. A systematic review was performed to evaluate the influence of SLC and ABC polymorphisms and their combinations on efficacy and safety in AML cohorts. Anthracycline intake was especially influenced by SLCO1B1 polymorphisms, associated with lower hepatic uptake, showing higher survival rates and toxicity in AML studies. The variant alleles of ABCB1 were related to anthracycline intracellular accumulation, increasing complete remission, survival and toxicity. Similar findings have been suggested with ABCC1 and ABCG2 polymorphisms. Polymorphisms of SLC29A1, responsible for cytarabine uptake, demonstrated significant associations with survival and response in Asian populations. Promising results were observed with SLC and ABC combinations regarding anthracycline toxicities. Knowledge of the role of transporter pharmacogenetics could explain the differences observed in drug disposition in the blast. Further studies including novel targeted therapies should be performed to determine the influence of genetic variability to individualize chemotherapy schemes.

Role of Pharmacogenetics in the Treatment of Acute Myeloid Leukemia: Systematic Review and Future Perspectives

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by remarkable toxicity and great variability in response to treatment. Plenteous pharmacogenetic studies have already been published for classical therapies, such as cytarabine or anthracyclines, but such studies remain scarce for newer drugs. There is evidence of the relevance of polymorphisms in response to treatment, although most studies have limitations in terms of cohort size or standardization of results. The different responses associated with genetic variability include both increased drug efficacy and toxicity and decreased response or resistance to treatment. A broad pharmacogenetic understanding may be useful in the design of dosing strategies and treatment guidelines. The aim of this study is to perform a review of the available publications and evidence related to the pharmacogenetics of AML, compiling those studies that may be useful in optimizing drug administration.

Update on drug transporter proteins in acute myeloid leukemia: Pathological implication and clinical setting

Acute myeloid leukemia (AML) is one of the most common hematological neoplasia causing death worldwide. The long-term overall survival is unsatisfactory due to many factors including older age, genetic heterogeneity and molecular characteristics comprising additional mutations, and resistance to chemotherapeutic drugs. The expression of ABCB1/P-glycoprotein, ABCC1/MRP1, ABCG2/BCRP and LRP transporter proteins is considered the major reason for multidrug resistance (MDR) in AML, however conflicting data have been reported. Here, we review the main issues about drug transporter proteins in AML clinical scenario, and highlight the clinicopathological significance of MDR phenotype associated with ABCB1 polymorphisms and FLT3 mutation.

Pharmacogenomics to Predict Tumor Therapy Response: A Focus on ATP-Binding Cassette Transporters and Cytochromes P450

Pharmacogenomics is an evolving tool of precision medicine. Recently, due to the introduction of next-generation sequencing and projects generating "Big Data", a plethora of new genetic variants in pharmacogenes have been discovered. Cancer resistance is a major complication often preventing successful anticancer treatments. Pharmacogenomics of both somatic mutations in tumor cells and germline variants may help optimize targeted treatments and improve the response to conventional oncological therapy. In addition, integrative approaches combining copy number variations and long noncoding RNA profiling with germline and somatic variations seem to be a promising approach as well. In pharmacology, expression and enzyme activity are traditionally the more studied aspects of ATP-binding cassette transporters and cytochromes P450. In this review, we briefly introduce the field of pharmacogenomics and the advancements driven by next-generation sequencing and outline the possible roles of genetic variation in the two large pharmacogene superfamilies. Although the evidence needs further substantiation, somatic and copy number variants as well as rare variants and common polymorphisms in these genes could all affect response to cancer therapy. Regulation by long noncoding RNAs has also been shown to play a role. However, in all these areas, more comprehensive studies on larger sets of patients are needed.

Tumor Drug Penetration Measurements Could Be the Neglected Piece of the Personalized Cancer Treatment Puzzle

Precision medicine aims to use patient genomic, epigenomic, specific drug dose, and other data to define disease patterns that may potentially lead to an improved treatment outcome. Personalized dosing regimens based on tumor drug penetration can play a critical role in this approach. State-of-the-art techniques to measure tumor drug penetration focus on systemic exposure, tissue penetration, cellular or molecular engagement, and expression of pharmacological activity. Using in silico methods, this information can be integrated to bridge the gap between the therapeutic regimen and the pharmacological link with clinical outcome. These methodologies are described, and challenges ahead are discussed. Supported by many examples, this review shows how the combination of these techniques provides enhanced patient-specific information on drug accessibility at the tumor tissue level, target binding, and downstream pharmacology. Our vision of how to apply tumor drug penetration measurements offers a roadmap for the clinical implementation of precision dosing.

A meta-analysis of MDR1 polymorphisms rs1128503 and rs1045642 and susceptibility to hepatocellular carcinoma

Objective

A relationship between polymorphisms rs1128503 and rs1045642 in the multidrug resistance 1 gene ( MDR1) and susceptibility to hepatocellular carcinoma (HCC) has been reported but is inconclusive. This study was performed to explore the significance of MDR1 polymorphisms rs1128503 and rs1045642 in screening and diagnosis of HCC.

Methods

Studies of association analyses between MDR1 gene polymorphisms rs1128503 and rs1045642 and HCC were selected from three foreign language databases (PubMed, Cochrane, and Embase) and three Chinese databases (Wanfang, China National Knowledge Infrastructure, and China Knowledge Network) and subjected to meta-analysis.

Results

We found no significant relationship between the rs1128503 polymorphism and susceptibility to HCC in 4 cohorts and no significant relationship between the rs1045642 polymorphism and susceptibility to HCC in 3 cohorts.

Conclusions

There was no relationship between polymorphisms rs1128503 or rs1045642 of the MDR1 gene and susceptibility to HCC.

The FLT3 inhibitor midostaurin selectively resensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic agents

The occurrence of multidrug resistance (MDR) associated with the overexpression of the ATP-binding cassette (ABC) protein ABCB1 in cancer cells remains a significant obstacle to successful cancer chemotherapy. Therefore, discovering modulators that are capable of inhibiting the drug efflux function or expression of ABCB1 and re-sensitizing multidrug-resistant cancer cells to anticancer agents is of great clinical importance. Regrettably, due to potential adverse events associated with drug-drug interactions and toxicity in patients, researchers have struggled to develop a synthetic inhibitor of ABCB1 that is clinically applicable to improve the effectiveness of chemotherapy. Alternatively, through drug repositioning of approved drugs, we discovered that the FMS-like tyrosine kinase-3 (FLT3) inhibitor midostaurin blocks the drug transport function of ABCB1 and re-sensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic drugs. Our findings were further supported by results demonstrating that midostaurin potentiates drug-induced apoptosis in ABCB1-overexpressing cancer cells and inhibits the ATPase activity of ABCB1. Considering that midostaurin is a clinically approved anticancer agent, our findings revealed an additional action of midostaurin and that patients with multidrug-resistant tumors may benefit from a combination therapy of midostaurin with standard chemotherapy, which should be further investigated.

Clinical utility of ABCB1 genotyping for preventing toxicity in treatment with irinotecan

Preventing severe irinotecan-induced adverse reactions would allow us to offer better treatment and improve patients' quality of life. Transporters, metabolizing enzymes, and genes involved in the folate pathway have been associated with irinotecan-induced toxicity. We analyzed 12 polymorphisms in UGT1A1, ABCB1, ABCG2, ABCC4, ABCC5, and MTHFR in 158 patients with metastatic colorectal cancer treated with irinotecan and studied the association with grade >2 adverse reactions (CTCAE). Among the most frequent ADRs, the SNPs rs1128503, rs2032582, and rs1045642 in ABCB1 and rs1801133 in MTHFR were associated with hematological toxicity and overall toxicity. The SNP rs11568678 in ABCC4 was also associated with overall toxicity. After correction of P values using a false discovery rate, only ABCB1 variants remained statistically significant. Haplotype analysis in ABCB1 showed an 11.3-fold and 4.6-fold increased risk of hematological toxicity (95% CI, 1.459-88.622) and overall toxicity (95% CI, 2.283-9.386), respectively. Consequently, genotyping of the three SNPs in ABCB1 can predict overall toxicity and hematological toxicity with a diagnostic odds ratio of 4.40 and 9.94, respectively. Genotyping of ABCB1 variants can help to prevent severe adverse reactions to irinotecan-based treatments in colorectal cancer.

Population Pharmacokinetics and Adverse Events of Erlotinib in Japanese Patients with Non-small-cell Lung Cancer: Impact of Genetic Polymorphisms in Metabolizing Enzymes and Transporters

Determinants of interindividual variability in erlotinib pharmacokinetics (PK) and adverse events remain to be elucidated. This study with 50 Japanese non-small-cell lung cancer patients treated with oral erlotinib at a standard dose of 150 mg aimed to investigate whether genetic polymorphisms affect erlotinib PK and adverse events. Single nucleotide polymorphisms (SNPs) in genes encoding metabolizing enzymes (CYP1A1, CYP1A2, CYP2D6, CYP3A4, CYP3A5, UGT1A1, UGT2B7, GSTM1, and GSTT1) or efflux transporters (ABCB1, and ABCG2) were analyzed as covariates in a population PK model. The ABCB1 1236C>T (rs1128503) polymorphism, not ABCB1*2 haplotype (1236TT-2677TT-3455TT, rs1128503 TT-rs2032582 TT-rs1045642 TT), was a significant covariate for the apparent clearance (CL/F), with the TT genotype showing a 29.4% decrease in CL/F as compared with the CC and the CT genotypes. A marginally higher incidence of adverse events (mainly skin rash) was observed in the TT genotype group; however, patients with high plasma erlotinib exposure did not always experience skin rash. None of the other SNPs affected PK or adverse events. The ABCB1 genotype is a potential predictor for erlotinib adverse events. Erlotinib might be used with careful monitoring of adverse events in patients with ABCB1 polymorphic variants.

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.

ATP-binding casette transporter expression in acute myeloid leukemia: association with in vitro cytotoxicity and prognostic markers

INTRODUCTION

Drug resistance and relapse are considered to be the major reasons for treatment failure in acute myeloid leukemia (AML). There is limited data on the role of ABC transporter expression on in vitro sensitivity to cytarabine (Ara-C) and daunorubicin (Dnr) in primary AML cells.

PATIENTS & METHODS

RNA expression levels of 12 ABC transporters were analyzed by real-time quantitative PCR in 233 de novo adult acute myeloid leukemia patients. Based on cytarabine or Dnr IC₅₀, the samples were categorized as sensitive, intermediate and resistant. Role of candidate ABC transporter RNA expression on in vitro cytotoxicity, treatment outcome post therapy as well as the influence of various prognostic markers on ABC transporter expression were analyzed.

RESULTS

Expression of ABCC3 and ABCB6 were significantly higher in Dnr-resistant samples when compared with Dnr-sensitive samples. Increased ABCC1 expression was associated with poor disease-free survival in this cohort of patients.

CONCLUSION

This comprehensive analysis suggests ABCC1, ABCC3, ABCB6 and ABCA5 as probable targets which can be modulated for improving chemotherapeutic responses.

Impact of ABC single nucleotide polymorphisms upon the efficacy and toxicity of induction chemotherapy in acute myeloid leukemia

Anthracycline uptake could be affected by efflux pumps of the ABC family. The influence of 7 SNPs of ABC genes was evaluated in 225 adult de novo acute myeloid leukemia (AML) patients. After multivariate logistic regression there were no significant differences in complete remission, though induction death was associated to ABCB1 triple variant haplotype (p = .020). The ABCB1 triple variant haplotype was related to higher nephrotoxicity (p = .016), as well as this haplotype and the variant allele of ABCB1 rs1128503, rs2032582 to hepatotoxicity (p = .001; p = .049; p < .001). Furthermore, the variant allele of ABCC1 rs4148350 was related to severe hepatotoxicity (p = .044), and the variant allele of ABCG2 rs2231142 was associated to greater cardiac (p = .004) and lung toxicities (p = .038). Delayed time to neutropenia recovery was observed with ABCB1 rs2032582 variant (p = .047). This study shows the impact of ABC polymorphisms in AML chemotherapy safety. Further prospective studies with larger population are needed to validate these associations.

Pharmacogenomics and the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a clinically and biologically heterogeneous malignancy that is primarily treated with combinations of cytarabine and anthracyclines. Although this scheme remains effective in most of the patients, variability of outcomes in patients has been partly related with their genetic variability. Several pharmacogenetic studies have analyzed the impact of polymorphisms in genes encoding transporters, metabolizers or molecular targets of chemotherapy agents. A systematic review on all eligible studies was carried out in order to estimate the effect of polymorphisms of anthracyclines and cytarabine pathways on efficacy and toxicity of AML treatment. Other emerging genes recently studied in AML, such as DNA repair genes, genes potentially related to chemotherapy response or AML prognosis, have also been included.