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- Kölz, Charlotte, et al.
(author)
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In silico and biological analyses of missense variants of the human biliary efflux transporter ABCC2 : effects of novel rare missense variants
- 2024
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In: British Journal of Pharmacology. - : British Pharmacological Society. - 0007-1188 .- 1476-5381.
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Journal article (peer-reviewed)abstract
- Background and PurposeThe ATP-dependent biliary efflux transporter ABCC2, also known as multidrug resistance protein 2 (MRP2), is essential for the cellular disposition and detoxification of various xenobiotics including drugs as well as endogenous metabolites. Common functionally relevant ABCC2 genetic variants significantly alter drug responses and contribute to side effects. The aim of this study was to determine functional consequences of rare variants identified in subjects with European ancestry using in silico tools and in vitro analyses.Experimental ApproachTargeted next-generation sequencing of the ABCC2 gene was used to identify novel variants in European subjects (n = 143). Twenty-six in silico tools were used to predict functional consequences. For biological validation, transport assays were carried out with membrane vesicles prepared from cell lines overexpressing the newly identified ABCC2 variants and estradiol β-glucuronide and carboxydichlorofluorescein as the substrates.Key ResultsThree novel rare ABCC2 missense variants were identified (W227R, K402T, V489F). Twenty-five in silico tools predicted W227R as damaging and one as potentially damaging. Prediction of functional consequences was not possible for K402T and V489F and for the common linked variants V1188E/C1515Y. Characterisation in vitro showed increased function of W227R, V489F and V1188E/C1515Y for both substrates, whereas K402T function was only increased for carboxydichlorofluorescein.Conclusion and ImplicationsIn silico tools were unable to accurately predict the substrate-dependent increase in function of ABCC2 missense variants. In vitro biological studies are required to accurately determine functional activity to avoid misleading consequences for drug therapy.
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| 2. |
- Rosmarin, Dan, et al.
(author)
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Genetic Markers of Toxicity From Capecitabine and Other Fluorouracil-Based Regimens : Investigation in the QUASAR2 Study, Systematic Review, and Meta-Analysis
- 2014
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In: Journal of Clinical Oncology. - 0732-183X .- 1527-7755. ; 32:10, s. 1031-1039
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Journal article (peer-reviewed)abstract
- PURPOSE: Fluourouracil (FU) is a mainstay of chemotherapy, although toxicities are common. Genetic biomarkers have been used to predict these adverse events, but their utility is uncertain.PATIENTS AND METHODS: We tested candidate polymorphisms identified from a systematic literature search for associations with capecitabine toxicity in 927 patients with colorectal cancer in the Quick and Simple and Reliable trial (QUASAR2). We then performed meta-analysis of QUASAR2 and 16 published studies (n = 4,855 patients) to examine the polymorphisms in various FU monotherapy and combination therapy regimens.RESULTS: Global capecitabine toxicity (grades 0/1/2 v grades 3/4/5) was associated with the rare, functional DPYD alleles 2846T>A and *2A (combined odds ratio, 5.51; P = .0013) and with the common TYMS polymorphisms 5'VNTR2R/3R and 3'UTR 6bp ins-del (combined odds ratio, 1.31; P = 9.4 × 10(-6)). There was weaker evidence that these polymorphisms predict toxicity from bolus and infusional FU monotherapy. No good evidence of association with toxicity was found for the remaining polymorphisms, including several currently included in predictive kits. No polymorphisms were associated with toxicity in combination regimens.CONCLUSION: A panel of genetic biomarkers for capecitabine monotherapy toxicity would currently comprise only the four DPYD and TYMS variants above. We estimate this test could provide 26% sensitivity, 86% specificity, and 49% positive predictive value-better than most available commercial kits, but suboptimal for clinical use. The test panel might be extended to include additional, rare DPYD variants functionally equivalent to *2A and 2846A, though insufficient evidence supports its use in bolus, infusional, or combination FU. There remains a need to identify further markers of FU toxicity for all regimens.
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| 3. |
- Weiss, Frederik, et al.
(author)
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Direct Quantification of Cytochromes P450 and Drug Transporters-A Rapid, Targeted Mass Spectrometry-Based Immunoassay Panel for Tissues and Cell Culture Lysates
- 2018
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In: Drug Metabolism And Disposition. - : AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS. - 0090-9556 .- 1521-009X. ; 46:4, s. 387-396
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Journal article (peer-reviewed)abstract
- The quantification of drug metabolizing enzymes and transporters has recently been revolutionized on the basis of targeted proteomic approaches. Isotope-labeled peptides are used as standards for the quantification of the corresponding proteins in enzymatically fragmented samples. However, hurdles in these approaches are low throughput and tedious sample prefractionation steps prior to mass spectrometry (MS) readout. We have developed an assay platform using sensitive and selective immunoprecipitation coupled with mass spectrometric readout allowing the quantification of proteins directly from whole cell lysates using less than 20,000 cells per analysis. Peptide group-specific antibodies (triple X proteomics antibodies) enable the enrichment of proteotypic peptides sharing a common terminus. These antibodies were employed to establish a MS-based immunoassay panel for the quantification of 14 cytochrome P450 (P450) enzymes and nine transporters. We analyzed the P450 enzyme and transporter levels in genotyped liver tissue homogenates and microsomes, and in samples from a time course induction experiment in human hepatocytes addressing different induction pathways. For the analysis of P450 enzymes and transporters only a minute amount of sample is required and no prefractionation is necessary, thus the assay platform bears the potential to bridge cell culture model experiments and results from whole organ tissue studies.
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