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  • 1
    In: Mutagenesis, 2015, Vol. 30(1), pp.51-57
    Description: The in vivo comet assay has recently been implemented into regulatory genotoxicity testing of pharmaceuticals with inclusion into the ICH S2R1 guidance. Regulatory genotoxicity testing aims to detect DNA alterations in form of gene mutations, larger scale chromosomal damage and recombination and aneuploidy. The ICH S2R1 guideline offers two options of standard batteries of tests for the detection of these endpoints. Both options start with an AMES assay and option 1 includes an in vitro mammalian cell assay and an in vivo micronucleus assay in rodent, whereas option 2 includes an in vivo micronucleus assay in bone marrow in rodent and a second in viv o assay in a second tissue with a second endpoint. The test recommended as second in vivo test is the comet assay in rat liver. The in vivo comet assay is considered as mature enough to ensure reliable detection of relevant in vivo genotoxicants in combination with the micronucleus test in bone marrow and the AMES assay. Although lots of research papers have been published using the in vitro comet assay, the in vitro version has not been implemented into official regulatory testing guidelines. A survey of the years 1999–2014 revealed 27 in vivo comet assays submitted to BfArM with market authorisation procedures, European and national advice procedures and clinical trial applications. In three procedures, in vitro comet assays had been submitted within the genetic toxicology packages.
    Keywords: Biology;
    ISSN: 0267-8357
    E-ISSN: 1464-3804
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 19 December 2017, Vol.114(51), pp.E10881-E10889
    Description: Interpretation of positive genotoxicity findings using the current in vitro testing battery is a major challenge to industry and regulatory agencies. These tests, especially mammalian cell assays, have high sensitivity but suffer from low specificity, leading to high rates of irrelevant positive findings (i.e., positive results in vitro that are not relevant to human cancer hazard). We developed an in vitro transcriptomic biomarker-based approach that provides biological relevance to positive genotoxicity assay data, particularly for in vitro chromosome damage assays, and propose its application for assessing the relevance of the in vitro positive results to carcinogenic hazard. The transcriptomic biomarker TGx-DDI (previously known as TGx-28.65) readily distinguishes DNA damage-inducing (DDI) agents from non-DDI agents. In this study, we demonstrated the ability of the biomarker to classify 45 test agents across a broad set of chemical classes as DDI or non-DDI. Furthermore, we assessed the biomarker's utility in derisking known irrelevant positive agents and evaluated its performance across analytical platforms. We correctly classified 90% (9 of 10) of chemicals with irrelevant positive findings in in vitro chromosome damage assays as negative. We developed a standardized experimental and analytical protocol for our transcriptomics biomarker, as well as an enhanced application of TGx-DDI for high-throughput cell-based genotoxicity testing using nCounter technology. This biomarker can be integrated in genetic hazard assessment as a follow-up to positive chromosome damage findings. In addition, we propose how it might be used in chemical screening and assessment. This approach offers an opportunity to significantly improve risk assessment and reduce cost.
    Keywords: DNA Damage Response ; Tgx-Ddi ; Genotoxicity ; High-Throughput Screening ; Transcriptomic Biomarker ; Biomarkers ; Gene Expression Profiling ; High-Throughput Screening Assays ; Mutagenicity Tests ; Transcriptome
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    In: Basic & Clinical Pharmacology & Toxicology, September 2017, Vol.121, pp.3-7
    Description: Byline: Jorn A. Holme, Roland Froetschl, Lisbeth E. Knudsen ***** No abstract is available for this article. *****
    Keywords: Mutagenesis;
    ISSN: 1742-7835
    E-ISSN: 1742-7843
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  • 4
    In: Ahmad, Aamir and Sarin, Navin and Engel, Florian and Kalayda, Ganna V. and Mannewitz, Mareike and Cinatl, Jindrich and Rothweiler, Florian and Michaelis, Martin and Saafan, Hisham and Ritter, Christoph A. and Jaehde, Ulrich and Frötschl, Roland (2017) Cisplatin resistance in non-small cell lung cancer cells is associated with an abrogation of cisplatin-induced G2/M cell cycle arrest. PLOS ONE, 12 (7). e0181081.
    Description: The efficacy of cisplatin-based chemotherapy in cancer is limited by the occurrence of innate and acquired drug resistance. In order to better understand the mechanisms underlying acquired cisplatin resistance, we have compared the adenocarcinoma-derived non-small cell lung cancer (NSCLC) cell line A549 and its cisplatin-resistant sub-line A549rCDDP2000 with regard to cisplatin resistance mechanisms including cellular platinum accumulation, DNA-adduct formation, cell cycle alterations, apoptosis induction and activation of key players of DNA damage response. In A549rCDDP2000 cells, a cisplatin-induced G2/M cell cycle arrest was lacking and apoptosis was reduced compared to A549 cells, although equitoxic cisplatin concentrations resulted in comparable platinum-DNA adduct levels. These differences were accompanied by changes in the expression of proteins involved in DNA damage response. In A549 cells, cisplatin exposure led to a significantly higher expression of genes coding for proteins mediating G2/M arrest and apoptosis (mouse double minute 2 homolog (MDM2), xeroderma pigmentosum complementation group C (XPC), stress inducible protein (SIP) and p21) compared to resistant cells. This was underlined by significantly higher protein levels of phosphorylated Ataxia telangiectasia mutated (pAtm) and p53 in A549 cells compared to their respective untreated control. The results were compiled in a preliminary model of resistance-associated signaling alterations. In conclusion, these findings suggest that acquired resistance of NSCLC cells against cisplatin is the consequence of altered signaling leading to reduced G2/M cell cycle arrest and apoptosis.
    ISSN: 1932-6203
    Source: University of Kent
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  • 5
    Language: English
    In: PLoS ONE, 01 January 2017, Vol.12(7), p.e0181081
    Description: The efficacy of cisplatin-based chemotherapy in cancer is limited by the occurrence of innate and acquired drug resistance. In order to better understand the mechanisms underlying acquired cisplatin resistance, we have compared the adenocarcinoma-derived non-small cell lung cancer (NSCLC) cell line A549 and its cisplatin-resistant sub-line A549rCDDP2000 with regard to cisplatin resistance mechanisms including cellular platinum accumulation, DNA-adduct formation, cell cycle alterations, apoptosis induction and activation of key players of DNA damage response. In A549rCDDP2000 cells, a cisplatin-induced G2/M cell cycle arrest was lacking and apoptosis was reduced compared to A549 cells, although equitoxic cisplatin concentrations resulted in comparable platinum-DNA adduct levels. These differences were accompanied by changes in the expression of proteins involved in DNA damage response. In A549 cells, cisplatin exposure led to a significantly higher expression of genes coding for proteins mediating G2/M arrest and apoptosis (mouse double minute 2 homolog (MDM2), xeroderma pigmentosum complementation group C (XPC), stress inducible protein (SIP) and p21) compared to resistant cells. This was underlined by significantly higher protein levels of phosphorylated Ataxia telangiectasia mutated (pAtm) and p53 in A549 cells compared to their respective untreated control. The results were compiled in a preliminary model of resistance-associated signaling alterations. In conclusion, these findings suggest that acquired resistance of NSCLC cells against cisplatin is the consequence of altered signaling leading to reduced G2/M cell cycle arrest and apoptosis.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 6
    Language: English
    In: Regulatory Toxicology and Pharmacology, June 2016, Vol.77, pp.25-34
    Description: Narrow Therapeutic Index Drugs (NTIDs) are characterized by a small range between therapeutic and toxicological effect. Missing international harmonized definition for NTIDs the EMA does not even have a definition of NTIDs in contrast to the U.S. FDA, Health Canada, and the Japanese NIHS. Sunitinib, a tyrosine kinase inhibitor (TKI), indicated for the treatment of certain cancer types, will be running off-patent soon. Falling into the category of NTID would have a major impact on regulatory requirements for generic applications. Our analyses of metadata revealed numerous arguments in favor of a NTID designation. We used in vitro experiments to also give initial experimental answers. Five cell types of different tissue origin were examined for determination of IC -values in cell viability assays. For comparison, the first-in-class TKI Imatinib was used as reference non-NTID drug. In addition, apoptotic proteins were investigated with respect to their expression and phosphorylation status. These in vitro experiments showed systematically higher toxicity of Sunitinib compared to Imatinib and a different expression and phosphorylation pattern of apoptotic proteins. In vitro data can only give preliminary results and further experiments with clinical blood samples and tumor biopsies are needed to finally clarify NTID status of Sunitinib.
    Keywords: Apoptosis ; Drug Safety ; Imatinib ; Narrow Therapeutic Index Drug (Ntid) ; Receptor Tyrosine Kinase (Rtk) ; Sunitinib ; Toxicity ; Tyrosine Kinase Inhibitor (Tki) ; Cell Viability ; Pharmacy, Therapeutics, & Pharmacology ; Public Health
    ISSN: 0273-2300
    E-ISSN: 1096-0295
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  • 7
    Book chapter
    Book chapter
    Elsevier Inc.
    Language: English
    In: Genetic Toxicology Testing, Chapter 10, pp.345-382
    Description: The in vivo comet assay is an extremely fast, flexible, and sensitive assay adaptable to a variety of exposure conditions and applicable to almost any tissue or cell type. This makes it an ideal option for the safety testing of new or previously tested products that require quick results, specific exposure conditions, and/or target organ assessments incompatible with other in vivo assays. The alkaline version can detect the direct DNA damaging effects of radical-forming chemicals, alkylating agents, adduct-forming chemicals, various metals, and UV or ionizing radiation. It can also detect DNA strand breaks indirectly induced by postinjury processes such as excision repair and inflammation. Because the comet assay does not require cells to undergo division prior to sampling, it is also ideal for testing exposures that may induce damage early or compounds that may degrade quickly. All potential applications and protocol variations of the assay cannot be covered in one book chapter. Therefore, this chapter just focuses on the critical components of conducting an in vivo comet assay test for regulatory submissions. The procedures presented include recommendations from the most recently adopted OECD Test Guideline 489 for the in vivo mammalian alkaline comet assay as well as recommendations by the authors for addressing the specific technical requirements of conducting a comet assay test and evaluating the results.
    Keywords: Comet assay test ; DNA damage ; target organs ; genotoxicity
    ISBN: 978-0-12-800764-8
    ISBN: 978-0-12-801006-8
    Source: ScienceDirect (Elsevier B.V.)
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  • 8
    Language: English
    In: International journal of clinical pharmacology and therapeutics, August 2017, Vol.55(8), pp.686-689
    Keywords: Antineoplastic Agents -- Therapeutic Use ; Carcinoma, Non-Small-Cell Lung -- Drug Therapy ; Cisplatin -- Therapeutic Use
    ISSN: 0946-1965
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  • 9
    In: Sarin, Navin and Engel, Florian and Kalayda, Ganna V and Frötschl, Roland and Cinatl, Jindrich and Rothweiler, Florian and Michaelis, Martin and Fröhlich, Holger and Jaehde, Ulrich (2016) Knowledge-based approach to identify key determinants of cisplatin sensitivity . International journal of clinical pharmacology and therapeutics, .
    Keywords: RM Therapeutics. Pharmacology
    ISSN: 0946-1965
    Source: University of Kent
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  • 10
    Language: English
    In: International Journal of Molecular Sciences, 01 March 2018, Vol.19(3), p.767
    Description: The major obstacle in the clinical use of the antitumor drug cisplatin is inherent and acquired resistance. Typically, cisplatin resistance is not restricted to a single mechanism demanding for a systems pharmacology approach to understand a whole cell’s reaction to the drug. In this study, the cellular transcriptome of untreated and cisplatin-treated A549 non-small cell lung cancer cells and their cisplatin-resistant sub-line A549rCDDP2000 was screened with a whole genome array for relevant gene candidates. By combining statistical methods with available gene annotations and without a previously defined hypothesis HRas, MAPK14 (p38), CCL2, DOK1 and PTK2B were identified as genes possibly relevant for cisplatin resistance. These and related genes were further validated on transcriptome (qRT-PCR) and proteome (Western blot) level to select candidates contributing to resistance. HRas, p38, CCL2, DOK1, PTK2B and JNK3 were integrated into a model of resistance-associated signalling alterations describing differential gene and protein expression between cisplatin-sensitive and -resistant cells in reaction to cisplatin exposure.
    Keywords: Cisplatin Resistance ; Cellular Signalling ; Hras ; P38 ; Ccl2 ; Dok1 ; Ptk2b ; Jnk3 ; Biology
    E-ISSN: 1422-0067
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