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Edwards, Arnelle (2023) Translational control of Human Epidermal Growth Factor Receptors, HER2 and HER4 in response to cellular stresses in breast cancer cells. PhD thesis, University of Nottingham.

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Abstract

The human epidermal growth factors (EGFR and HER2-4) are tyrosine kinase cell surface receptors that play key roles in cell signalling, growth, and differentiation. However, HER2 and HER4 are commonly overexpressed in breast cancer contributing to breast cancer aggressiveness.

Translational mechanisms such as internal ribosome entry sites (IRESs) and upstream opening reading frames (uORFs) can mediate translation of specific mRNA under cell stress conditions when global translation is inhibited. Cancer cells can be exposed to many cell stress conditions such as hypoxia and nutrient starvation, and such translational control mechanisms can contribute to overexpression of mRNAs. EGFR mRNA contains an IRES in the 5’ untranslated region (5’ UTR) that maintains expression of a firefly luciferase reporter in response to stress conditions such as hypoxia. However, it is not known if the 5’ UTRs of the other HER family members (HER 2-4) contain an IRES. Additionally, HER2 mRNA contains a repressive uORF in the 5’ UTR and a translational derepression element (TDE) in the 3’ UTR. However, it has not been investigated whether HER2 5’ UTR can mediate an increase in translation in response to glutamine or glucose starvation as seen for ATF4 and GCN4 mRNA.

To screen for IRES activity in HER2 or HER4 5’ UTRs, bicistronic luciferase constructs were created that contained the 5’ UTR of HER2 or HER4 between two luciferase reporters. In contrast to EGFR 5’ UTR, there was no evidence of IRES activity in the 5’ UTRs of HER2 and HER4 in response to endoplasmic reticulum stress, oxidative stress, low serum conditions, a hypoxia mimic, genotoxic stress, confluence stress, glutamine starvation and glucose starvation in MCF-7 breast cancer cells.

Additionally, monocistronic constructs were created that contained the 5’ UTRs of HER2 or HER4 upstream to a single firefly luciferase reporter. In monocistronic constructs, HER2 and HER4 5’ UTRs did not increase translation in response to glutamine or glucose starvation in MCF-7 cells. Finally, in contrast to a previous publication, the TDE in HER2 3’ UTR did not derepress translation under non-stressed conditions or additionally in response to glutamine or glucose starvation.

The work in this thesis investigated the translational control of important oncogenes in stress conditions that are biologically relevant to cancer. Despite not identifying any translational control mechanisms in HER2 or HER4 5’ UTRs, the work in this thesis provides a promising approach for characterising the translational control of other important oncogenes that could provide potential therapeutic targets for cancer therapy in the future.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Spriggs, Keith De Moor, Cornelia Jopling, Catherine
Keywords:	human epidermal growth factors, cell receptors, cancer cells, breast cancer, therapeutics
Subjects:	Q Science > QH Natural history. Biology > QH573 Cytology R Medicine > RC Internal medicine > RC 254 Neoplasms. Tumors. Oncology (including Cancer) R Medicine > RM Therapeutics. Pharmacology
Faculties/Schools:	UK Campuses > Faculty of Science > School of Pharmacy
Item ID:	76478
Depositing User:	Edwards, Arnelle
Date Deposited:	27 Mar 2024 13:04
Last Modified:	27 Mar 2024 13:04
URI:	https://eprints.nottingham.ac.uk/id/eprint/76478

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