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Title: Understanding the role of the tumour microenvironment in chemoresistance and tumour progression
Author: Ireland, Lucy Victoria
ISNI:       0000 0004 7656 7652
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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Cancer resistance to therapies and metastasis remain two of the biggest challenges in the cancer field. Solid tumours are characteristically surrounded by a stroma. The tumour stroma is composed of non-malignant stromal cells and extracellular matrix proteins. Tumour-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are the most abundant cell types in the tumour stroma and can affect cancer resistance to therapies and metastasis. However, how exactly TAMs and CAFs confer chemoresistance towards tumour cells and support metastasis is only partly elucidated. Two solid tumours which acquire resistance to their standard therapies and exhibit high rates of metastasis are pancreatic ductal adenocarcinoma (PDAC) and invasive breast cancer. Both tumour types possess a rich tumour microenvironment (TME) which partakes in bi-directional signalling with tumour cells to confer survival as well as promote metastasis and growth. However, the exact mechanisms by which TAMs and CAFs promote resistance to therapies and metastasis in these cancers are not fully understood. The aims of this thesis were 1) to elucidate how TAMs and CAFs in the TME of PDAC and invasive breast cancer promote tumour cell survival and resistance to chemotherapy. 2) To investigate the effect of blocking the mechanisms of therapy resistance identified, in combination with standard chemotherapy, in preclinical PDAC and breast cancer mouse models recapitulative of the human disease. 3) To identify factors supporting PDAC metastasis identification of factors mediating tumour progression. Using primary isolated macrophages and pancreatic stellate cells (PaSCs) in vitro identified insulin-like growth factor 1 and 2 (IGF-1/2) as secreted factors which activate insulin and IGF-1 receptors on tumour cells on both PDAC and breast cancer cells. Isolation of tumour cells, non-immune stromal cells and macrophages from orthotopic PDAC and TNBC-like invasive breast cancer models revealed non-immune stromal cells and macrophages as the main sources of IGF-1 and IGF-2 activating insulin/IGF-1R on tumour cells in vivo. Blockade of IGF signalling using an IGF-blocking antibody in combination with standard chemotherapy resulted in a decrease in tumour cell proliferation in PDAC and a decrease in primary breast tumour size and reduction in total metastatic burden in an invasive breast cancer model. These studies provide the rationale to trial IGF-blocking antibodies in combination with chemotherapy in PDAC and breast cancer patients. Investigation into the metastatic potential of three PDAC cell lines, FC1199, FC1242 and FC1245, derived from the genetically engineered KPC (Kras LSL.G12D/+; p53R172H/+; PdxCretg/+) mouse model showed that these cells possessed varied aggressiveness and metastatic propensity. Implantation of FC1245 cells resulted in mice having a severely reduced quality of life and reduced life expectancy to around 20 days after implantation. FC1245-tumour bearing mice exhibited both spontaneous liver and lung metastasis at higher levels compared to the other implanted mice. Stable isotope labelling with amino acids in cell culture (SILAC) proteomic analysis of the three cell lines revealed nineteen consistently upregulated proteins from FC1245 cells, of which mesothelin was identified as one of the top candidates upregulated in the highly metastatic FC1245 cells. Immunohistochemical analysis of PDAC tissues revealed that mesothelin expression was limited to the tumour tissue. Mesothelin expression by FC1245 cells was also confirmed by immunoblotting analysis. Overall, this work has identified new therapeutic targets IGF-1 and IGF-2 to combat chemoresistance in both PDAC and breast cancer which trialled in preclinical models, in combination with chemotherapy, has shown a more favourable outcome compared to standard chemotherapy alone. This work has also identified mesothelin as a potential protein of interest in metastatic PDAC.
Supervisor: Mielgo Iza, Ainhoa Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral