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Title: The Epidermal Growth Factor Receptor : a target for the treatment of non-small cell lung cancer
Author: Smith, Oliver
ISNI:       0000 0004 9354 2975
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2020
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Upregulation and mutation of EGFR has been linked to many diseases, particularly non-small cell lung cancer (NSCLC), which accounts for approximately 80% of lung cancer cases. In 2015, the EGFR inhibitor osimertinib (trade name Tagrisso) was approved by the US FDA for the treatment of NSCLC treat patients with tumours expressing a double mutant form of EGFR that lead to previous 1st generation EGFR inhibitors (geftinib and erlotinib) becoming ineffective. Unfortunately further resistance to osimertinib occurs in >50% of patients, with the acquisition of a cysteine to serine (C797S) mutant being the most common driver of resistance. Circulating free DNA (cfDNA) is currently used to select patients for treatment with osimertinib. This approach can sensitively detect EGFR mutant tumours, but gives no information about tumour size or heterogeneity within the tumour or between any metastatic sites. The development of a mutant-specific positron emission tomography (PET) probe would allow for the possibility of imaging the individual tumour masses, therefore giving information which cfDNA cannot provide. Building on the success of osimertinib as a structural template, [11C]- osimertinib was developed as PET probe. An in vivo study in nude mice was conducted to explore the effect of [11C]-osimertinib in activating and double mutant NSCLC xenografts, which demonstrated that the tumours could be imaged based on the accumulation of the probe in tumours expressing both mutant forms. Activation of EGFR by EGF results in homo-dimerisation and subsequent internalisation. Several known inhibitors for treatment of NSCLC have been found to stop the activation of EGFR, however the exact effects of different mutation patterns or inhibitors on internalisation are not well understood. A more in depth understanding the mechanism of inhibitors may lead to development of further treatment pathways for NSCLC, therefore a method was developed to detect EGFR internalisation across a range of cell types. Levels of surface EGFR and EGF/EGFR internalisation was studied using established cell lines, confirming that mutant EGFR expressing cells have dysregulated EGFR signalling but also demonstrating that this remains under at least partial controlled by EGF stimulation and is kinase-dependant in all cell types studied. This mutation stops the irreversible binding which is essential for high occupancy and inhibition of T790M mutant EGFR forms. Again, the successes of the EGFR inhibitors were harnessed in the development of EGFR PROTACs, a new technology that functions by hijacking the proteasomal degradation system in cells to selectively degrade targeted proteins. As this process is not driven by occupancy alone this mechanism has the potential to target the EGFR C797S mutant. Several EGFR PROTACs were designed, synthesised and tested in vitro using immunoblotting to test this hypothesis. Three main areas were explored for the development 22 of EGFR PROTACs: EGFR selective warheads, linker length and different E3 ligase binders. The optimal PROTACs demonstrated the capability to degrade T790M EGFR with a reversible compound, but only at relatively high compound concentrations.
Supervisor: Butterworth, Sam ; Whitehead, Roger ; Finegan, Katherine Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available