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Title: Integrating c-Met molecular imaging into the optimisation of cancer therapy
Author: Arulappu, Appitha
ISNI:       0000 0004 5994 5818
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2016
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Basal-like subtypes of breast cancer (BLBC) account for about 15-20% of all breast cancer, affecting younger women (<50 years old) of predominantly African and Hispanic descent [1] with rapid relapse ([2]. c-Met is overexpressed in various solid tumors, lung, breast, ovary, kidney, colon, thyroid, liver, and gastric carcinomas [3]; [4]; [5]; [6]; [7]; [8]; [9]; [10]; [11]; [12]; [13]; [14]. In breast cancer, a higher c-Met expression level is displayed in BLBC in comparison to other intrinsic breast cancer subtypes [15] . In the first part of this thesis, the basal-like breast tumour xenograft mouse model was used to investigate early signs of locoregional recurrence of primary tumour using a 18F radiolabelled c-Met binding peptide, [18F]AH113804. [18F]AH113804 exhibited significantly higher uptake in the tumours (in comparison to mammary fatty tissue) with a target to background (muscle) ratio of approximately 3:1 (p<0.01). In addition to this, [18F]AH113804 was able to detect local tumor recurrence as early as six days after tumour resection [16]. Following publication of this work, I designed an in-house radiolabelled single chain Fv-Fc fusion against human c-Met, which was selected from a phage display library, and labelled with Cy5 dye initially. It was then labelled with the radioisotope 111In that was conjugated with the chelator CHX-A‟‟DTPA for an increase in radiolabelling efficiency. Both the optical and the radiolabelled version of the scFv-Fc were injected into dual tumour-bearing female mice. The tracer‟s uptakes at the c-Met positive tumour (basal-like breast tumour) and in the c-Met negative but ER positive breast adenocarcinoma), were visualised using an optical detector (for the Cy5 labelled tracer) and a gamma camera (using the SPECT tracer). We detect a higher uptake in the c-Met positive basal-like breast tumour in comparison to the c-Met negative control tumours using both versions of the tracer. EGFR expression has been reported in at least 50% of basal-like breast cancers (BLBCs) [17]. Due to the essential role of EGFR in both proliferation and cell survival pathways in breast epithelium and other epithelia, EGFR inhibitors have been used in clinical trials to treat patients with BLBC [18]. Unfortunately, this was shown to be of limited success [19]. There is a need to gain a deeper understanding of EGFR signalling in order to identify potential therapeutic targets. In the third part of this thesis, assays were carried out to investigate further the effect of PTPN11 knockdown on EGFR and c-Met phosphorylation, cell proliferation and E-cadherin level of expression in basal like breast cancer cells. PTPN11 was identified as an EGFR modulator based on the outcome from a high content screen based on FRET sensing of EGFR activity in situ, monitored by fluorescence lifetime imaging (FLIM). Validation of this novel regulator of EGFR activity in BLBC confirmed a significant slowing of the kinetics of EGFR dephosphorylation upon ligand stimulation, as well as c-Met hyperphosphorylation in cells that were depleted of PTPN11 in PTPN11-silenced cells following EGF stimulation.
Supervisor: Gillett, Cheryl Elaine ; Ng, Tony Tsz-cheong Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available