Identification of differential nutrient starvation responses.



Poursaitidis, I
(2018) Identification of differential nutrient starvation responses. PhD thesis, University of Liverpool.

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Abstract

To promote survival and proliferation cancer cells re-programme their metabolism, altering both uptake and utilisation of extracellular nutrients. To examine correspondences between nutrient supply and viability, in order to identify targetable requirements, I individually depleted amino acid nutrients from diploid Human Mammary Epithelial (HME) isogenic cells expressing commonly activated oncogenes. Cystine deprivation was found to induce massive-oxidative stress associated-cell death of HME cells expressing an activated epidermal growth factor receptor (EGFR). Cell death occurred via an iron-dependent mode, known as ferroptosis associated with increased generation of reactive oxygen species and lipid peroxidation. Pharmacological inhibition of EGFR or mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) signalling was found to block ferroptosis and ROS production and was associated with increased expression of glutathione peroxidase 4 (GPX4). Suppression of GPX4 expression in wild-type or gefitinib-treated HME-EGFR cells was sufficient to sensitise cells to ferroptosis. Importantly, MAPK signals were also important in suppressing cell-cell contact and communication that was found to provide an essential line of defence against ferroptosis induction and spread. In this way, microscopic observation of ferroptosis in wild-type HME cells identified a cell death spread phenotype that is consistent with necrosis phenotypes observed in ischemic models. Inhibition of ROS generation and lipid peroxidation effectively blocked the progression of necrosis indicating that counteracting lipid peroxidation might be beneficial for degenerative conditions where lipid peroxidation is evident. Additional therapeutic application of my findings was modelled using non-small lung cancer cell (NSCLC) lines with overactive ERK signalling. These cells were found to be sensitive to ferroptosis following deprivation of cystine in vitro as well as in vivo where in systemic deprivation of cystine was achieved in xenografted mice following administration of a cystine-degrading enzyme. Taken together, my results show that the presence of common oncogenic mutations can render cells sensitive to the depletion of a specific nutrient, and further suggest potentially novel anti-cancer therapies based on the inability of some MAPK-driven cancer cells to overcome oxidative stress following nutrient depletion, as well as therapies to limit the spreading phenotype of ferroptosis in cells associated with other diseases such as Alzheimer’s Disease, or that occur in normal cells in response to ischemic reperfusion and acute kidney injuries.

Item Type: Thesis (PhD)
Divisions: Faculty of Health and Life Sciences > Faculty of Health and Life Sciences
Depositing User: Symplectic Admin
Date Deposited: 28 Aug 2018 10:28
Last Modified: 04 Aug 2021 07:11
DOI: 10.17638/03019213
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3019213