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Investigating the role of Annexin A2 in Epidermal Growth Factor (EGF) induced signalling in cancer
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Authors
Advisor(s)
Abstract(s)
Reactive oxygen species (ROS) are produced as a consequence of cellular metabolism and
can also be produced by the cell in response to growth factor/growth factor receptor
stimulation to function as second messengers in major signalling pathways. Recently,
increasing evidence has revealed that the ROS, H2O2 is an important second messenger in
cellular signal transduction, because of its high diffusion and ability to selectively target
reactive cysteine residues in proteins. Currently, H2O2-mediated signalling has been
implicated in several fundamental physiological processes such as cell proliferation,
differentiation, migration and apoptosis. EGF/EGFR is one of the most mutated GF/GFR
associations in cancer thanks to its role in tumorigenesis. The binding of EGF to EGFR
induces downstream events leading to intracellular production of H2O2 for signalling. Cancer
cells characteristically exhibit increased ROS levels compared to normal counterparts that
gives them a proliferative advantage and promotes cancer progression. To balance the
advantage of low ROS levels (nanomolar concentration for proliferative signalling pathways)
against its damaging effect (as a specific oxidant at high concentrations), cancer cells induce
the cellular antioxidant response. Our laboratory identified a novel redox regulatory protein,
annexin A2 (ANXA2) and showed that its antioxidant function plays a crucial role in
supporting tumour growth and chemoresistance. As a logical follow up to this research we
investigated the role played by ANXA2 in oncogenic signalling pathways induced by EGF.
Here, the activation of signalling pathways in pre-established MDA MB 231 breast cancer
cell lines with knockdown for ANXA2 and respective control cells was investigated by
western blotting upon treatment of these cells with 50 ng/ml of EGF at different time points.
Biotinylated Iodoacetamide (BIAM) assays were done to assess the oxidation of reactive Cys
residues in redox sensitive proteins upon treatment with EGF. Intracellular ROS levels and
cell proliferation were also analysed in ANXA2 depleted versus control cancer cells upon
treatment with EGF. Our results show that ANXA2 depletion in MDA MB 231 cancer cells
leads to enhanced activation of the pro-survival and pro-proliferative PI3K/Akt signalling
pathway, enhanced ROS production and increased proliferation rate upon EGF treatment
compared to control cells. EGF treatment also led to oxidation/inhibition of the main
regulator of the PI3K/Akt pathway, PTEN. Interestingly, we observed upregulation of PRDX
II (a redox regulatory protein) in ANXA2 depleted MDA MB 231 cells. Taken together, our
results demonstrate that ANXA2 plays a redox regulatory role in EGF induced ROSmediated
PI3K/Akt signalling and that ANXA2 knockdown cells might be upregulating
PRDX II to compensate for the loss of the ANXA2 redox regulatory protein.
Description
Dissertação de mestrado, Qualidade em Análises, Faculdade de Ciências e Tecnologia, Universidade do Algarve; Universitat de Barcelona; Gdansk University of Technology, Universidad de Cádiz, Universitas Bergensis; 2015
Keywords
Análises laboratoriais Oxigénio Células Metabolismo Cancro