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Developing an in vitro repeat-dose approach to detect non-genotoxic carcinogens (NGCs) / DEMI PRITCHARD

Swansea University Author: DEMI PRITCHARD

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    Copyright: The Author, Demi Jade Pritchard, 2024.

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DOI (Published version): 10.23889/SUthesis.66287

Abstract

This work aimed to develop an in vitro testing battery, to detect non-genotoxic carcinogens (NGCs). Currently, in vitro test systems aim at detecting genotoxic carcinogens (GCs) whereas, the gold standard test for NGCs is the two-year rodent bioassay. There are numerous problems with this method suc...

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Published: Swansea, Wales, UK 2024
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Pritchard, Demi J. ; Chapman, Katherin E. ; Doak, Shareen H. ; Jenkins, Gareth J. S.
URI: https://cronfa.swan.ac.uk/Record/cronfa66287
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Abstract: This work aimed to develop an in vitro testing battery, to detect non-genotoxic carcinogens (NGCs). Currently, in vitro test systems aim at detecting genotoxic carcinogens (GCs) whereas, the gold standard test for NGCs is the two-year rodent bioassay. There are numerous problems with this method such as long experimental periods, high costs and many ethical concerns. NGCs make up ̴15% of all carcinogens, highlighting the importance of their correct detection and labelling. The in vitro test battery includes a selection of endpoints comprised primarily from the hallmarks of cancer. The endpoints explored were acute and chronic genotoxicity assessment via the mononucleated micronucleus (Mn) assay; cytotoxicity assessment utilising RPD; cell cycle and apoptosis assessment using flow cytometry; gene expression analysis using a PCR array and determining mitochondrial health using the Seahorse analyser. Six carcinogens were assessed using the multi-endpoint, in vitro testing system. These chemicals included nickel chloride (NiCl2), sodium meta arsenite (NaMAr), cacodylic acid (GC- included to compare with NaMAr), rosuvastatin, chloroprene and 2,3,7,8-tetrachlorodibenzodioxin (TCDD). This work showed that some NGCs can behave as GCs so there may be some mislabelling of carcinogens. NaMAr indicated genotoxicity due to a chronic dosing approachand NiCl2 also showed genotoxicity but in an acute setting. The correct categorisation of these carcinogens is of increasing importance due to the use in consumer product for example. The in vitro battery appears to be a promising first step in detecting and understanding the mechanism(s) of action (MoA) used by different NGCs. This work highlighted some potentially mislabelled NGCs, such as NiCl2 and NaMAr, which is an important novel finding. The PCR array proved to be very useful to identify genes of interest, that could help unpick the MoA of each diverse NGC. Next steps could include utilising a targeted three-dimensional (3D) spheroid approach based on the exposure route (E.g. Rosuvastatin is ingested so a gut model). Chronic dosing is an important real-life component of the test battery and is required to improve the whole picture. These additional approaches, together with an in vitro test battery, could improve detection and provide a complete narrative of the MoAs utilized by these complex carcinogens.
Keywords: Genetic toxicology, Non-genotoxic carcinogens, cancer, micronucleus assay
College: Faculty of Medicine, Health and Life Sciences
Funders: NC3Rs (JAF1056-100)