Association Study of a Functional Variant on ABCG2 Gene with Sunitinib-Induced Severe Adverse Drug Reaction

A systematic review and meta-analysis of the impacts of germline pharmacogenomics on severe toxicity and symptom burden in adult patients with cancer

The clinical application of Pharmacogenomics (PGx) has improved patient safety. However, comprehensive PGx testing has not been widely adopted in clinical practice, and significant opportunities exist to further optimize PGx in cancer care. This systematic review and meta-analysis aim to evaluate the safety outcomes of reported PGx-guided strategies (Analysis 1) and identify well-studied emerging pharmacogenomic variants that predict severe toxicity and symptom burden (Analysis 2) in patients with cancer. We searched MEDLINE, EMBASE, CENTRAL, clinicaltrials.gov, and International Clinical Trials Registry Platform from inception to January 2023 for clinical trials or comparative studies evaluating PGx strategies or unconfirmed pharmacogenomic variants. The primary outcomes were severe adverse events (SAE; ≥ grade 3) or symptom burden with pain and vomiting as defined by trial protocols and assessed by trial investigators. We calculated pooled overall relative risk (RR) and 95% confidence interval (95%CI) using random effects models. PROSPERO, registration number CRD42023421277. Of 6811 records screened, six studies were included for Analysis 1, 55 studies for Analysis 2. Meta-analysis 1 (five trials, 1892 participants) showed a lower absolute incidence of SAEs with PGx-guided strategies compared to usual therapy, 16.1% versus 34.0% (RR = 0.72, 95%CI 0.57-0.91, p = 0.006, I2 = 34%). Meta-analyses 2 identified nine medicine(class)-variant pairs of interest across the TYMS, ABCB1, UGT1A1, HLA-DRB1, and OPRM1 genes. Application of PGx significantly reduced rates of SAEs in patients with cancer. Emergent medicine-variant pairs herald further research into the expansion and optimization of PGx to improve systemic anti-cancer and supportive care medicine safety and efficacy.

CYP450 and drug efflux transporters polymorphism influence clinical outcomes of Thai osimertinib-treated non-small cell lung cancer patients

Background: Osimertinib has shown greater efficacy than standard epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and fewer grade 3 or higher adverse drug reactions (ADRs) in patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations. However, the clinical outcomes of osimertinib treatment vary depending on the patient's ethnicity. Therefore, further research is necessary to evaluate the impact of single nucleotide polymorphisms (SNPs) in cytochrome P450 (CYP450) and drug transporters on the therapeutic outcomes and ADRs to osimertinib in Thai patients, to provide improved pharmacological treatments for cancer patients. Methods: This retrospective and prospective cohort study enrolled 63 Thai patients with NSCLC treated with 80 mg of osimertinib once daily as monotherapy. Seventeen SNPs in candidate genes related to drug metabolism and transport pathways were analyzed in each patient. Chi-square or Fisher's exact tests were used to evaluate the associations between SNPs and clinical outcomes, including ADR incidence and objective response rate (ORR). In addition, the correlation between the genotype and median time to treatment failure (TTF) or progression-free survival (PFS) was assessed using Kaplan-Meier analysis and a log-rank test. Results: We identified six SNPs (rs2231142 and rs2622604 in ABCG2, rs762551 in CYP1A2, rs1057910 in CYP2C9, rs28371759 in CYP3A4, and CYP2A6 deletion polymorphism (CYP2A6*4)) that significantly increased the incidence of ADRs. In addition, we found two SNPs (rs2069514 in CYP1A2 and rs1057910 in CYP2C9) that significantly decreased the median TTF, and two SNPs (rs28399433 in CYP2A6 and rs1057910 in CYP2C9) that significantly decreased the median progression-free survival (PFS). Specifically, we found that one of these SNPs (rs1057910 in CYP2C9) influenced ADRs, TTF, and PFS. Additionally, SNPs in the CYP2A6 heterozygous variant (non4/*4) significantly increased ADR incidence, leading to a high frequency of dose reduction (27.0%). Conclusion: Our study demonstrated significant SNPs associated with increased ADR incidence, decreased PFS, and decreased TTF in Thai patients with NSCLC treated with osimertinib. The CYP2C9 (*3) and CYP2A6 (*4) allele frequencies differed between ethnicities and were associated with an increased incidence of ADRs. These findings highlight the importance of considering genetic factors in NSCLC treatment and may facilitate personalized medicine approaches. Moreover, our study showed a higher incidence of ADRs than the previous trials, including FLAURA and AURA2, and a higher frequency of dose reduction than reported in the AURA 3 trial, possibly due to genetic differences among the study populations.

ABCG2 and SLCO1B1 gene polymorphisms in the Croatian population

BACKGROUND

Organic anion-transporting polypeptide 1B1 (OATP1B1) and the ATP-binding cassette subfamily G member 2, ABCG2, are important transporters involved in the transport of endogenous substrates and xenobiotics, including drugs. Genetic polymorphisms of these transporters have effect on transporter activity. There is significant interethnic variability in the frequency of allele variants.

AIM

To determined allele and genotype frequencies of ABCG2 and SLCO1B1 genes in Croatian populations of European descent.

SUBJECTS AND METHODS

A total of 905 subjects (482 women) were included. Genotyping for ABCG2 c.421C > A (rs2231142) and for SLCO1B1 c.521T > C (rs4149056), was performed by real-time polymerase chain reaction (PCR) using TaqMan^® DME Genotyping Assays.

RESULTS

For ABCG2 c.421C > A, the frequency of CC, CA and AA genotypes was 81.4%, 17.8% and 0.8% respectively. The frequency of variant ABCG2 421 A allele was 9.7%. For SLCO1B1 c.521T > C, the frequency of TT, TC and CC genotypes was 61.7%, 34.8% and 3.5% respectively. The frequency of variant SLCO1B1 521 C allele was 20.9%.

CONCLUSION

The frequency of the ABCG2 and SLCO1B1 allelic variants and genotypes in the Croatian population is in accordance with other European populations. Pharmacogenetic analysis can serve to individualise drug therapy and minimise the risk of developing adverse drug reactions.

Role and Regulation of Hepatobiliary ATP-Binding Cassette Transporters during Chemical-Induced Liver Injury

Severity of drug-induced liver injury (DILI) ranges from mild, asymptomatic, and transient elevations in liver function tests to irreversible liver damage, often needing transplantation. Traditionally, DILI is classified mechanistically as high-frequency intrinsic DILI, commonly dose dependent or DILI that rarely occurs and is idiosyncratic in nature. This latter form is not dose dependent and has a pattern of histopathological manifestation that is not always uniform. Currently, a third type of DILI called indirect hepatotoxicity has been described that is associated with the pharmacological action of the drug. Historically, DILI was primarily linked to drug metabolism events; however, the impact of transporter-mediated rates of drug uptake and excretion has gained greater prominence in DILI research. This review provides a comprehensive view of the major findings from studies examining the contribution of hepatic ATP-binding cassette transporters as key contributors to DILI and how changes in their expression and function influence the development, severity, and overall toxicity outcome. SIGNIFICANCE STATEMENT: Drug-induced liver injury (DILI) continues to be a focal point in drug development research. ATP-binding cassette (ABC) transporters have emerged as important determinants of drug detoxification, disposition, and safety. This review article provides a comprehensive analysis of the literature addressing: (a) the role of hepatic ABC transporters in DILI, (b) the influence of genetic mutations in ABC transporters on DILI, and (c) new areas of research emphasis, such as the influence of the gut microbiota and epigenetic regulation, on ABC transporters.

Characteristics of Gut Microbiota in Patients With Clear Cell Renal Cell Carcinoma

Different gut microbiota is implicated in different diseases, including cancer. However, gut microbiota differences between individuals with clear cell renal cell carcinoma (ccRCC) and healthy individuals are unclear. Here, we analyzed gut microbiota composition in 51 ccRCC patients and 40 healthy controls using 16S rRNA sequencing analysis. We observed that Blautia, Streptococcus, [Ruminococcus]_torques_group, Romboutsia, and [Eubacterium]_hallii_group were dominant and positively associated with ccRCC. We isolated and cultured Streptococcus lutetiensis to characterize specific gut microbiota that promotes ccRCC and found that it promoted in vitro ccRCC proliferation, migration, and invasion via the TGF-signaling pathway. Interactions identified between the gut microbiota and ccRCC suggest the gut microbiota could serve as a potential non-invasive tool for predicting ccRCC risk and also function as a cancer therapy target.

Genome-Wide Meta-Analysis Identifies Variants in DSCAM and PDLIM3 That Correlate with Efficacy Outcomes in Metastatic Renal Cell Carcinoma Patients Treated with Sunitinib

Individual response to sunitinib in metastatic renal cell carcinoma (mRCC) patients is highly variable. Earlier, sunitinib outcome was related to single nucleotide polymorphisms (SNPs) in CYP3A5 and ABCB1. Our aim is to provide novel insights into biological mechanisms underlying sunitinib action. We included mRCC patients from the European EuroTARGET consortium (n = 550) and the RIKEN cohort in Japan (n = 204) which were analysed separately and in a meta-analysis of genome-wide association studies (GWAS). SNPs were tested for association with progression-free survival (PFS) and overall survival (OS) using Cox regression. Summary statistics were combined using a fixed effect meta-analysis. SNP rs28520013 in PDLIM3 and the correlated SNPs rs2205096 and rs111356738 both in DSCAM, showed genome-wide significance (p < 5 × 10−8) with PFS and OS in the meta-analysis. The variant T-allele of rs28520013 associated with an inferior PFS of 5.1 months compared to 12.5 months in non-carriers (p = 4.02 × 10−10, HR = 7.26). T-allele carriers of rs28520013 showed an inferior OS of 6.9 months versus 30.2 months in non-carriers (p = 1.62 × 10−8, HR = 5.96). In this GWAS we identified novel genetic variants in PDLIM3 and DSCAM that impact PFS and OS in mRCC patients receiving sunitinib. The underlying link between the identified genes and the molecular mechanisms of sunitinib action needs to be elucidated.

Medically Important Alterations in Transport Function and Trafficking of ABCG2

Several polymorphisms and mutations in the human ABCG2 multidrug transporter result in reduced plasma membrane expression and/or diminished transport function. Since ABCG2 plays a pivotal role in uric acid clearance, its malfunction may lead to hyperuricemia and gout. On the other hand, ABCG2 residing in various barrier tissues is involved in the innate defense mechanisms of the body; thus, genetic alterations in ABCG2 may modify the absorption, distribution, excretion of potentially toxic endo- and exogenous substances. In turn, this can lead either to altered therapy responses or to drug-related toxic reactions. This paper reviews the various types of mutations and polymorphisms in ABCG2, as well as the ways how altered cellular processing, trafficking, and transport activity of the protein can contribute to phenotypic manifestations. In addition, the various methods used for the identification of the impairments in ABCG2 variants and the different approaches to correct these defects are overviewed.

Meta-Analysis of ABCG2 and ABCB1 Polymorphisms With Sunitinib-Induced Toxicity and Efficacy in Renal Cell Carcinoma

Background: ABCG2 and ABCB1 are genes related to the pharmacokinetics of sunitinib and have been associated with its toxicity and efficacy. However, the results have been controversial. This study aimed to evaluate the associations of ABCG2 and ABCB1 polymorphisms with sunitinib-induced toxicity and efficacy in renal cell carcinoma (RCC) by meta-analysis. Methods: PubMed, EMBASE, Cochrane Library, and Web of Science were systematically searched for studies investigating the associations of the ABCG2 rs2231142 polymorphism with sunitinib-induced toxicity and the associations of the ABCB1 rs1128503 and ABCB1 rs2032582 polymorphisms with sunitinib-induced toxicity and clinical outcomes. The associations were evaluated by effect size (ES) with 95% confidence intervals (CIs). Results: Eight and five studies were included in the toxicity and efficacy analysis, respectively, including a total of 1081 RCC patients. The ABCG2 rs2231142 A allele was associated with an increased risk of sunitinib-induced thrombocytopenia and hand-foot syndrome (HFS) in Asians (ES = 1.65, 95% CI = 1.15-2.36, p = 0.006; ES = 1.52, 95% CI = 1.02-2.27, p = 0.041). However, the ABCG2 rs2231142 polymorphism was not associated with sunitinib-induced hypertension or neutropenia (ES = 1.09, 95% CI = 0.69-1.73, p = 0.701; ES = 0.87, 95% CI = 0.57-1.31, p = 0.501). Compared with the C allele, the ABCB1 rs1128503 T allele was associated with a decreased risk of sunitinib-induced hypertension but worse progression-free survival (PFS) (ES = 0.44, 95% CI = 0.26-0.77, p = 0.004; ES = 1.36, 95% CI = 1.07-1.73, p = 0.011). There was no significant association between the T allele or C allele of ABCB1 rs1128503 and overall survival (OS) (ES = 0.82, 95% CI = 0.61-1.10, p = 0.184). The ABCB1 rs2032582 T allele was associated with worse PFS than the other alleles (ES = 1.46, 95% CI = 1.14-1.87, p = 0.003), while there was no significant association between the T allele or other alleles and sunitinib-induced hypertension, HFS, or OS (ES = 0.77, 95% CI = 0.46-1.29, p = 0.326; ES = 1.02, 95% CI = 0.65-1.62, p = 0.919; ES = 1.32, 95% CI = 0.85-2.05, p = 0.215). Conclusion: The results indicate that the ABCG2 rs2231142 polymorphism may serve as a predictor of sunitinib-induced thrombocytopenia and HFS in Asians, while the ABCB1 rs1128503 polymorphism may serve as a predictor of sunitinib-induced hypertension, and both the ABCB1 rs1128503 and rs2032582 polymorphisms may serve as predictors of PFS in RCC. These results suggest a possible application of individualized use of sunitinib according to the genetic background of patients.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

The ABCG2/BCRP transporter and its variants - from structure to pathology

The ABCG2 protein has a key role in the transport of a wide range of structurally dissimilar endo- and xenobiotics in the human body, especially in the tissue barriers and the metabolizing or secreting organs. The human ABCG2 gene harbors a high number of polymorphisms and mutations, which may significantly modulate its expression and function. Recent high-resolution structural data, complemented with molecular dynamic simulations, may significantly help to understand intramolecular movements and substrate handling, as well as the effects of mutations on the membrane transporter function of ABCG2. As reviewed here, structural alterations may result not only in direct alterations in drug binding and transporter activity, but also in improper folding or problems in the carefully regulated process of trafficking, including vesicular transport, endocytosis, recycling, and degradation. Here, we also review the clinical importance of altered ABCG2 expression and function in general drug metabolism, cancer multidrug resistance, and impaired uric acid excretion, leading to gout.

Pharmacogenetics for severe adverse drug reactions induced by molecular-targeted therapy

Molecular-targeted drugs specifically interfere with molecules that are frequently overexpressed or mutated in cancer cells. As such, these drugs are generally considered to precisely attack cancer cells, thereby inducing fewer adverse drug reactions (ADRs). However, molecular-targeted drugs can still cause characteristic ADRs that, although rarely severe, can be life-threatening. Therefore, it is becoming increasingly important to be able to predict which patients are at risk of developing ADRs after treatment with molecular-targeted therapy. The emerging field of pharmacogenetics aims to better distinguish the genetic variants associated with drug toxicity and efficacy to improve the selection of therapeutic strategies for each genetic profile. Here, we provide an overview of the current reports on the relationship between genetic variants and molecular-targeted drug-induced severe ADRs in oncology.

The road map of cancer precision medicine with the innovation of advanced cancer detection technology and personalized immunotherapy

The advancement of cancer genomics research due to the development of next generation sequencing technologies is going to bring the promise of cancer precision medicine, in turn revolutionizing cancer detection and treatment. In this review, we will discuss the possible road map for implementation of cancer precision medicine into the clinical practice by mainly focusing on the role of liquid biopsy, particularly circulating tumor DNA, as a potential tool for cancer screening, selection of an appropriate drug(s), surveillance of minimal residual diseases, and early detection of recurrence. We will also review the current status of genome-driven oncology and emerging field of immunotherapies that could be provided to patients to improve their clinical outcome and quality of life. Lastly, we will discuss the usefulness of artificial intelligence that facilitate complex data integration in our health care/medical care system.

Cellular Processing of the ABCG2 Transporter-Potential Effects on Gout and Drug Metabolism

The human ABCG2 is an important plasma membrane multidrug transporter, involved in uric acid secretion, modulation of absorption of drugs, and in drug resistance of cancer cells. Variants of the ABCG2 transporter, affecting cellular processing and trafficking, have been shown to cause gout and increased drug toxicity. In this paper, we overview the key cellular pathways involved in the processing and trafficking of large membrane proteins, focusing on ABC transporters. We discuss the information available for disease-causing polymorphic variants and selected mutations of ABCG2, causing increased degradation and impaired travelling of the transporter to the plasma membrane. In addition, we provide a detailed in silico analysis of an as yet unrecognized loop region of the ABCG2 protein, in which a recently discovered mutation may actually promote ABCG2 membrane expression. We suggest that post-translational modifications in this unstructured loop at the cytoplasmic surface of the protein may have special influence on ABCG2 processing and trafficking.

Impact of Q141K on the Transport of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors by ABCG2

The ATP-binding cassette transporter ABCG2 is expressed in various organs, such as the small intestine, liver, and kidney, and influences the pharmacokinetics of drugs that are its substrates. ABCG2 is also expressed by cancer cells and mediates resistance to anticancer agents by promoting the efflux of these drugs. In the present study, we investigated the interactions between epidermal growth factor receptor tyrosine kinase inhibitors and ABCG2 by MTT assay, intracellular drug accumulation assay, and FACS. This study showed that four epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs) (gefitinib, erlotinib, lapatinib, and afatinib) were transported from tumor cells as substrates of ABCG2. Q141K is a common single-nucleotide polymorphism of ABCG2 in Asians. We demonstrated that the extracellular efflux of gefitinib, erlotinib, and lapatinib was reduced by Q141K, whereas afatinib transport was not affected. In addition, all four EGFR TKIs inhibited the transport of other substrates by both wild-type and variant ABCG2 at 0.1 μM concentrations. Accordingly, epidermal growth factor receptor tyrosine kinase inhibitors may induce interactions with other drugs that are substrates of ABCG2, and single-nucleotide polymorphisms of ABCG2 may influence both the pharmacokinetics and efficacy of these anticancer agents.

Development of precision medicine approaches based on inter-individual variability of BCRP/ABCG2

Precision medicine is a rapidly-developing modality of medicine in human healthcare. Based on each patient׳s unique characteristics, more accurate dosages and drug selection can be made to achieve better therapeutic efficacy and less adverse reactions in precision medicine. A patient׳s individual parameters that affect drug transporter action can be used to develop a precision medicine guidance, due to the fact that therapeutic efficacy and adverse reactions of drugs can both be affected by expression and function of drug transporters on the cell membrane surface. The purpose of this review is to summarize unique characteristics of human breast cancer resistant protein (BCRP) and the genetic variability in the BCRP encoded gene ABCG2 in the development of precision medicine. Inter-individual variability of BCRP/ABCG2 can impact choices and outcomes of drug treatment for several diseases, including cancer chemotherapy. Several factors have been implicated in expression and function of BCRP, including genetic, epigenetic, physiologic, pathologic, and environmental factors. Understanding the roles of these factors in controlling expression and function of BCRP is critical for the development of precision medicine based on BCRP-mediated drug transport.

ABCG2 Polymorphism rs2231142 and hypothyroidism in metastatic renal cell carcinoma patients treated with sunitinib

BACKGROUND AND AIM

Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) cause significant adverse events including thyroid dysfunction, mainly hypothyroidism, in a considerable proportion of patients. In a series of metastatic renal cell carcinoma (mRCC) patients treated with sunitinib, we aimed to study the correlation between hypothyroidism and single nucleotide polymorphisms (SNPs) in genes involved in sunitinib pharmacokinetics and pharmacodynamics.

PATIENTS AND METHODS

We included 79 mRCC patients who started sunitinib between November 2005 and March 2016. Serum thyroid function markers were collected at start and during sunitinib therapy. Germ-line DNA genotyping for 16 SNPs in 8 candidate genes was performed. Endpoints were time to increase in thyroid stimulating hormone (TSH) and time to decrease in T4 or free T4 (FT4) on day 1 and day 28 of each sunitinib cycle.

RESULTS

Patients with the ABCG2 rs2231142 CC-genotype had a significantly longer time-to-TSH-increase on day 1 (11 vs. 5 cycles; p = 0.0011), and time-to-T4/FT4-decrease on day 1 (not reached vs. 10 cycles; p = 0.013) and day 28 (28 vs. 7 cycles; p = 0.03) compared to CA-carriers. Patients with the CYP3A5 rs776746 GG-genotype had a significantly longer time-to-TSH-increase at day 1 compared to GA-patients: 11 vs. 5 cycles (p = 0.0071). Significant associations were also found between PDGFRA rs35597368 and rs1800812 and time-to-TSH-increase at day 28.

CONCLUSION

Polymorphism rs2231142 in the efflux pump ABCG2 is associated with hypothyroidism in mRCC patients treated with sunitinib.

The Roles of Common Variation and Somatic Mutation in Cancer Pharmacogenomics

Cancer pharmacogenomics is the science concerned with understanding genetic alterations and its effects on the pharmacokinetics and pharmacodynamics of anti-cancer drugs, with the aim to provide cancer patients with the precise medication that will achieve a good response and cause low/no incidence of adverse events. Advances in biotechnology and bioinformatics have enabled genomic research to evolve from the evaluation of alterations at the single-gene level to studies on the whole-genome scale using large-scale genotyping and next generation sequencing techniques. International collaborative efforts have resulted in the construction of databases to curate the identified genetic alterations that are clinically significant, and these are currently utilized in clinical sequencing and liquid biopsy screening/monitoring. Furthermore, countless clinical studies have accumulated sufficient evidence to match cancer patients to therapies by utilizing the information of clinical-relevant alterations. In this review we summarize the importance of germline alterations that act as predictive biomarkers for drug-induced toxicity and drug response as well as somatic mutations in cancer cells that function as drug targets. The integration of genomics into the medical field has transformed the era of cancer therapy from one-size-fits-all to cancer precision medicine.

ABC Family Transporters

The transport of specific molecules across lipid membranes is an essential function of all living organisms. The processes are usually mediated by specific transporters. One of the largest transporter families is the ATP-binding cassette (ABC) family. More than 40 ABC transporters have been identified in human, which are divided into 7 subfamilies (ABCA to ABCG) based on their gene structure, amino acid sequence, domain organization, and phylogenetic analysis. Of them, at least 11 ABC transporters including P-glycoprotein (P-GP/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2) are involved in multidrug resistance (MDR) development. These ABC transporters are expressed in various tissues such as the liver, intestine, kidney, and brain, playing important roles in absorption, distribution, and excretion of drugs. Some ABC transporters are also involved in diverse cellular processes such as maintenance of osmotic homeostasis, antigen processing, cell division, immunity, cholesterol, and lipid trafficking. Several human diseases such as cystic fibrosis, sitosterolemia, Tangier disease, intrahepatic cholestasis, and retinal degeneration are associated with mutations in corresponding transporters. This chapter will describe function and expression of several ABC transporters (such as P-GP, BCRP, and MRPs), their substrates and inhibitors, as well as their clinical significance.

Roles of pharmacogenomics in non-anthracycline antineoplastic-induced cardiovascular toxicities: A systematic review and meta-analysis of genotypes effect

BACKGROUND

Exploration on genetic roles in antineoplastic-related cardiovascular toxicity has increased with the advancement of genotyping technology. However, knowledge on the extent of genetic determinants in affecting the susceptibility to the cardiovascular toxicities of antineoplastic is limited. This study aims to identify potential single nucleotide polymorphism (SNP) in predicting non-anthracycline antineoplastic-related cardiovascular toxicity.

METHODS

We systematically searched for original research in PubMed, Cochrane Central Register of Controlled Studies, CINAHL Plus, EMBASE and HuGE Navigator from database inception until January 2018. Studies on association between polymorphism and antineoplastic-induced cardiovascular toxicity in patients treated for cancer of all antineoplastic agents were included except for anthracycline. Case reports, conference abstracts, reviews and non-patient studies were excluded. Data extracted by two independent reviewers were combined with random-effects model and reported according to PRISMA and MOOSE guidelines.

RESULTS

The 35 studies included examined a total of 219 SNPs in 80 genes, 11 antineoplastic and 5 types of cardiovascular toxicities. Meta-analyses showed that human epidermal growth factor receptor 2 (HER2) rs1136201, a risk variants (pooled OR: 2.43; 1.17-5.06, p = 0.018) is a potential predictors for trastuzumab-related cardiotoxicity. Gene dose effect analysis showed number of variant allele may contribute to the risk too.

CONCLUSIONS

This review found that HER2 rs1136201 can have the potential in predicting trastuzumab-related heart failure. As such, further studies are needed to confirm the validity of these results as well as determine the economic aspect of using SNPs prior to its implementation as a clinical practice.

Polymorphisms of the Multidrug Pump ABCG2: A Systematic Review of Their Effect on Protein Expression, Function, and Drug Pharmacokinetics

The widespread expression and polyspecificity of the multidrug ABCG2 efflux transporter make it an important determinant of the pharmacokinetics of a variety of substrate drugs. Null ABCG2 expression has been linked to the Junior blood group. Polymorphisms affecting the expression or function of ABCG2 may have clinically important roles in drug disposition and efficacy. The most well-studied single nucleotide polymorphism (SNP), Q141K (421C>A), is shown to decrease ABCG2 expression and activity, resulting in increased total drug exposure and decreased resistance to various substrates. The effect of Q141K can be rationalized by inspection of the ABCG2 structure, and the effects of this SNP on protein processing may make it a target for pharmacological intervention. The V12M SNP (34G>A) appears to improve outcomes in cancer patients treated with tyrosine kinase inhibitors, but the reasons for this are yet to be established, and this residue's role in the mechanism of the protein is unexplored by current biochemical and structural approaches. Research into the less-common polymorphisms is confined to in vitro studies, with several polymorphisms shown to decrease resistance to anticancer agents such as SN-38 and mitoxantrone. In this review, we present a systematic analysis of the effects of ABCG2 polymorphisms on ABCG2 function and drug pharmacokinetics. Where possible, we use recent structural advances to present a molecular interpretation of the effects of SNPs and indicate where we need further in vitro experiments to fully resolve how SNPs impact ABCG2 function.

Polymorphisms of ABCG2 and its impact on clinical relevance

Human ABCG2 is one of the most important ATP-binding cassette (ABC) transporters. This protein functions as a xenobiotic transporter of large, hydrophobic, positively or negatively charged molecules, a wide variety anticancer drugs, fluorescent dyes, and different toxic compounds found in normal food. SNPs in ABCG2 may affect absorption and distribution of these substrates, altering the accumulation, effectiveness and toxicity of compounds or drugs in large populations. Its transport properties have been implicated clinically and ABCG2 expression is linked with different disease states. We reviewed the SNPs of ABCG2 in clinical relevance about gout, acute myeloid leukemia, solid tumors, and other diseases.

Curcumin as an In Vivo Selective Intestinal Breast Cancer Resistance Protein Inhibitor in Cynomolgus Monkeys

To estimate the clinical impact of pharmacokinetic modulation via breast cancer resistance protein (BCRP), in vivo approaches in nonclinical settings are desired in drug development. Clinical observation has identified curcumin as a promising candidate for in vivo selective BCRP inhibition, in addition to several well known inhibitors, such as lapatinib and pantoprazole. This study aimed to confirm the inhibitory efficacy of curcumin on gastrointestinal BCRP function in cynomolgus monkeys and to perform comparisons with lapatinib and pantoprazole. Oral area under the plasma concentration-time curve (AUC) and bioavailability of well known BCRP (sulfasalazine and rosuvastatin), P-glycoprotein (fexofenadine, aliskiren, and talinolol), and CYP3A (midazolam) substrates were investigated in the presence and absence of inhibitors. Oral exposures of sulfasalazine and rosuvastatin were markedly elevated by curcumin with minimal changes in systemic clearance, whereas pharmacokinetic alterations after fexofenadine, aliskiren, and talinolol oral exposure were limited. Curcumin increased oral midazolam exposure without affecting systemic clearance, presumably owing to partial inhibition of intestinal CYP3A. Lapatinib increased the oral AUC for sulfasalazine to a greater extent than curcumin did, whereas pantoprazole had a smaller effect. However, lapatinib also exerted significant effects on fexofenadine, failed to selectively discriminate between BCRP and P-glycoprotein inhibition, and had an effect on oral midazolam exposure comparable with that of curcumin. Thus, pharmacokinetic evaluation in monkeys demonstrated that pretreatment with curcumin as an in vivo selective BCRP inhibitor was more appropriate than pretreatment with lapatinib and pantoprazole for the assessment of the impact of BCRP on gastrointestinal absorption in nonrodent models.

Genetic polymorphisms associated with adverse reactions of molecular-targeted therapies in renal cell carcinoma

The prognosis of patients with metastatic renal cell carcinoma has drastically improved due to the development of molecular-targeted drugs and their use in clinical practice. However, these drugs cause some diverse adverse reactions in patients and sometimes affect clinical outcomes of cancer therapy. Therefore, predictive markers are necessary to avoid severe adverse reactions, to establish novel and effective prevention methods, and to improve treatment outcomes. Some genetic factors involved in these adverse reactions have been reported; however, perspectives on each adverse response have not been integrated yet. In this review, genetic polymorphisms relating to molecular-targeted therapy-induced adverse reactions in patients with renal cell carcinoma are summarized in the points of pharmacokinetic and pharmacodynamic mechanisms. We also discuss about the relationship between systemic drug exposure and adverse drug reactions.

Association analysis of SNPs present in plasma with adverse events and population pharmacokinetics in Chinese sunitinib treated patients with renal cell carcinoma

Background

Sunitinib is a tyrosine kinase inhibitor with effective therapeutic outcomes in patients with renal-cell carcinoma. The study were to analyze the association of single-nucleotide polymorphisms present in cell-free DNA and pharmacokinetics with sunitinib treatment-emergent adverse events in Chinese patients with renal-cell carcinoma.

Materials and Methods

We genotyped 8 keys SNPs in 6 candidate genes. The plasma concentrations of sunitinib and N-desethyl sunitinib were measured using a high performance liquid chromatography-tandam mass spectrometry method. Correlations between the single-nucleotide polymorphisms and adverse events were investigated by univariate and multivariate logistic regression and we quantitatively evaluated the effect of single-nucleotide polymorphisms on the pharmacokinetics of sunitinib by using a population PK model.

Results

Necessary dose reductions of sunitinib were significantly correlated with SNP rs1933437 in FLT3. A higher severity of AEs were collected with SNP rs2032582 in ABCB1 and rs1800812 in PDGFRα. Thrombocytopenia was collected with rs1800812 in PDGFRα. Our study provides a population PK model of sunitinib with the ABCB1 genotype as a predictive covariate for apparent oral clearance.

Conclusions

Our study preliminarily confirmed the hypothesis that the pharmacokinetics of sunitinib is affected by the SNPs of enzyme in Chinese renal-cell carcinoma patients, and this affects the different distribution and severity of adverse events of sunitinib.

Reverse Translational Research of ABCG2 (BCRP) in Human Disease and Drug Response

Reverse translational research takes a bedside-to-bench approach, using sophisticated basic research to explain the biological mechanisms behind observed clinical data. For transporters, which play a role in human disease and drug response, this approach offers a distinct advantage over the typical translational research, which often falters due to inadequate in vitro and preclinical animal models. Research on ABCG2, which encodes the Breast Cancer Resistance Protein, has benefited immensely from a reverse translational approach due to its broad implications for disease susceptibility and both therapeutic and adverse drug response. In this review, we describe the success of reverse translational research for ABCG2 and opportunities for further studies.

ABCMdb reloaded: updates on mutations in ATP binding cassette proteins

ABC (ATP-Binding Cassette) proteins with altered function are responsible for numerous human diseases. To aid the selection of positions and amino acids for ABC structure/function studies we have generated a database, ABCMdb (Gyimesi et al., ABCMdb: a database for the comparative analysis of protein mutations in ABC transporters, and a potential framework for a general application. Hum Mutat 2012; 33:1547–1556.), with interactive tools. The database has been populated with mentions of mutations extracted from full text papers, alignments and structural models. In the new version of the database we aimed to collect the effect of mutations from databases including ClinVar. Because of the low number of available data, even in the case of the widely studied disease-causing ABC proteins, we also included the possible effects of mutations based on SNAP2 and PROVEAN predictions. To aid the interpretation of variations in non-coding regions, the database was supplemented with related DNA level information. Our results emphasize the importance of in silico predictions because of the sparse information available on variants and suggest that mutations at analogous positions in homologous ABC proteins have a strong predictive power for the effects of mutations. Our improved ABCMdb advances the design of both experimental studies and meta-analyses in order to understand drug interactions of ABC proteins and the effects of mutations on functional expression.

Database URL:http://abcm2.hegelab.org

Continuous remission of renal cell carcinoma with tumour thrombus after severe adverse events following short-term treatment with sunitinib

A 64-year-old Japanese man with renal cell carcinoma (RCC) and tumour thrombus in the inferior vena cava was treated with sunitinib. Two weeks after treatment, he was hospitalised for disturbance of consciousness. Laboratory tests revealed high-grade hypoglycaemia, hyponatraemia, liver dysfunction and thrombocytopaenia with disseminated intravascular coagulation. Sunitinib was discontinued and the patient recovered after a protracted platelet transfusion. At 5 months after treatment, CT revealed that the tumour thrombus had disappeared and other lesions had regressed. MRI at 15 months revealed further regression and suggested the possibility of histological remission according to the signal intensity of fibrosis. A partial response persisted at 20 months after treatment, despite residual accumulation in the renal tumour evident on positron emission tomography. In summary, we present a case of locally advanced RCC accompanied by severe adverse events that showed a significant and durable response to treatment with sunitinib for just 2 weeks.

Transporter genes ABCG2 rs2231142 and ABCB1 rs1128503 polymorphisms and atorvastatin response in Chilean subjects

WHAT IS KNOWN AND OBJECTIVE

Statins are first-line therapy for reducing high cholesterol levels. However, response to these drugs shows high interindividual variability. We aimed to investigate the influence of two single nucleotide polymorphisms (SNP) (ABCB1 rs1128503 and ABCG2 rs2231142) in the ABC transporter genes on response to short-term low-dose atorvastatin in Chilean hypercholesterolaemic patients.

METHODS

We studied 127 Chilean hypercholesterolaemic patients treated with 10 mg/d atorvastatin for 4 weeks. The lipid profile was determined before and after drug administration. Genotyping of the rs1128503 and rs2231142 variants was performed using TaqMan^® Drug Metabolism Genotyping Assays.

RESULTS AND DISCUSSION

Genotype distribution for all polymorphisms investigated was consistent with the Hardy-Weinberg equilibrium. Atorvastatin reduced TC, LDL-C and TG concentrations (P<.05), whereas HDL-C levels were found to be increased (P<.05). Minor allele frequencies for rs1128503 and rs2231142 variants were 0.453 and 0.075, respectively. In this study, patients prescribed with short-term low-dose atorvastatin and carrying ABCB1 (rs1128503) or ABCG2 (rs2231142) SNPs did not show differences in LDL-C response (P>.05).

WHAT IS NEW AND CONCLUSION

The ABCB1 SNP was not associated with response to atorvastatin in Chilean subjects. The few ABCG2 421A homozygotes did not allow meaningful inferences to be made for this polymorphism.

Effects of VEGF and VEGFR polymorphisms on the outcome of patients with metastatic renal cell carcinoma treated with sunitinib: a systematic review and meta-analysis

To summarize and clarify the association between vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor (VEGFR) polymorphisms and the outcome in patients with metastatic renal cell carcinoma (mRCC) treated with sunitinib. A total of 8 studies including 900 patients were analyzed in this systematic review after screening the database of PubMed, EMBASE and Web of Science. Hazard ratios (HRs) with 95% confidence interval (CI) were used to evaluate the strength of the association. VEGFR1 rs9582036 AA/AC carriers and rs9554320 CC/AC carriers had more favorable overall survival (OS) in patients with mRCC treated with sunitinib (n = 3), but not in progression-free survival (PFS). In addition, VEGFA rs2010963 was associated with poorer PFS of mRCC (n = 1). VEGFA rs699947 was significant in predicting PFS by univariate analysis, but showed no statistical significance in OS (n = 1). VEGFR2 rs1870377 was verified to be associated with sunitinib OS (n = 1). Furthermore, patients with VEGFR3 rs307826 and rs307821 had shorter PFS and OS during sunitinib therapy (n = 2, respectively). Our results suggested that VEGF and VEGFR polymorphisms were associated with outcomes in sunitinib treated mRCC patients, especially VEGFR1 polymorphisms. However, considering the limited study numbers, its clinical application in sunitinib treated mRCC still needs further confirmation.

Gene-gene and gene-environment interactions influence platinum-based chemotherapy response and toxicity in non-small cell lung cancer patients

Platinum-based chemotherapy is a major therapeutic regimen of lung cancer. Various single nucleotide polymorphisms (SNPs) reported were associated with platinum-based chemotherapy response and drug toxicity. However, neither of the studies explored this association from SNP-SNP interaction perspective nor taking into effects of SNP-environment consideration simultaneously. We genotyped 504 polymorphisms and explore the association of gene-gene and gene-environment interactions with platinum-based chemotherapy response and toxicity in 490 NSCLC patients. 16 SNPs were found significantly associated with platinum-based chemotherapy, and they were picked out as study object in the validation cohort. We recruited 788 patients in the validation cohort. We found that HSPD1 rs17730989-SUMF1 rs2633851 interaction was associated with platinum-based chemotherapy-induced hematologic toxicity (adjusted OR = 0.233, P = 0.018). In addition, the combined effect of ABCG2 rs2231142-CES5A rs3859104 was significantly associated with overall toxicity (adjusted OR = 8.044, P = 4.350 × 10-5). Besides, the model of ARHGAP26 rs3776332-ERCC6 rs2228528-SLC2A1 rs4658-histology was associated with platinum-based chemotherapeutic response. Gene-gene and gene-environment interactions have been identified to contribute to chemotherapy sensitivity and toxicity. They can potentially predict drug response and toxicity of platinum-based chemotherapy in NSCLC patients.

Description of the EuroTARGET cohort: A European collaborative project on TArgeted therapy in renal cell cancer-GEnetic- and tumor-related biomarkers for response and toxicity

OBJECTIVE

For patients with metastatic renal cell cancer (mRCC), treatment choice is mainly based on clinical parameters. With many treatments available and the limited response to treatment and associated toxicities, there is much interest in identifying better biomarkers for personalized treatment. EuroTARGET aims to identify and characterize host- and tumor-related biomarkers for prediction of response to tyrosine kinase inhibitor therapy in mRCC. Here, we describe the EuroTARGET mRCC patient cohort.

METHODS AND MATERIALS

EuroTARGET is a European collaborative project designed as an observational study for which patients with mRCC were recruited prospectively in 62 centers. In addition, 462 patients with mRCC from previous studies were included. Detailed clinical information (baseline and follow-up) from all patients was entered in web-based case record forms. Blood was collected for germline DNA and pharmacokinetic/pharmacodynamic analyses and, where available, fresh-frozen tumor material was collected to perform tumor DNA, RNA, kinome, and methylome analyses.

RESULTS

In total, 1,210 patients with mRCC were included. Of these, 920 received a tyrosine kinase inhibitor as first-line targeted treatment (sunitinib [N = 713, 78%], sorafenib [N = 41, 4%], or pazopanib [N = 166, 18%]) and had at least 6 months of outcome assessment (median follow-up 15.3 months [interquartile range: 8.5-30.2 months]). Germline DNA samples were available from 824 of these patients, fresh-frozen tumor material from 142 patients, fresh-frozen normal kidney tissue from 95 patients, and tissue microarrays created from formalin-fixed paraffin-embedded tumor material from 247 patients. Of the 920 patients, germline DNA variant chip data were successfully generated for 811 patients (Illumina HumanOmniExpress BeadChip). For 80 patients, next-generation exome sequencing of germline and tumor DNA was performed, tumor RNA sequencing was performed for 124 patients, kinome activity measured and processed for 121 patients (PamChip), and methylome data (Illumina Infinium HumanMethylation450 BeadChip) were created for 116 RCC tissues (and 23 normal kidney tissues). For 73 out of the 920 patients, all platform data types were generated. In addition, 40 patients were included in a pharmacokinetic/pharmacodynamic phase IV substudy.

CONCLUSIONS

Analysis of EuroTARGET cohort data will contribute to personalization of therapy for patients with mRCC. The extensive clinical data and multiplatform EuroTARGET data will be freely available.

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.

Genomewide Association Studies in Pharmacogenomics: Meeting Report of the NIH Pharmacogenomics Research Network-RIKEN (PGRN-RIKEN) Collaboration

Genomewide association studies (GWAS) have resulted in the identification of many heritable genetic factors that underlie risk for human disease or variation in physiologic traits. In contrast, there are fewer GWAS of drug response phenotypes, despite extensive unexplained interindividual variability. To address this urgent need, the NIH Pharmacogenomics Research Network (PGRN) and the Center for Integrative Medical Sciences (IMS) at RIKEN support a collaboration, PGRN-RIKEN, with the goal of accelerating GWAS of drug response phenotypes.