Investigating the cooperation of APC and KRAS mutations in colorectal cancer

Gay, David Michael (2018) Investigating the cooperation of APC and KRAS mutations in colorectal cancer. PhD thesis, University of Glasgow.

Abstract

Colorectal Cancer (CRC) progresses in a stepwise manner accumulating mutations in particular signalling pathways. Despite our knowledge of the genetic progression of the disease, the resulting phenotypes of the different mutation combinations remains poorly understood. I used genetically engineered mouse models to investigate the cooperation of two frequent early mutations - loss of the tumour suppressor gene APC and activating KRAS mutations, to try and identify potential therapeutic targets.
Hyperactivated Wnt signalling is a hallmark of CRC, although efficacious therapies are limited. In chapter 3 I focussed on targeting this pathway at the level of β-catenin mediated transcription. I showed that deletion of BLC9 and BCL9l, two proteins involved in β-catenin mediated transcription, suppresses proliferation and the expression of a subset of Wnt target genes following loss of APC and KRAS activation. I showed that these two proteins are dispensable intestinal homeostasis. I also showed that deletion of BCL9 and BCL9l significantly accelerated tumour initiation.
In chapter 4 I performed unbiased quantitative proteomics on crypt cultures from VillinCreER Apcfl/fl (APC) and VillinCreER Apcfl/fl KrasG12D/+ (APC KRAS) mice to identify deregulated signalling pathways between these two genotypes. I identified a ‘nutrient stress’ phenotype in APC KRAS crypts. I show that this might be driven by a significant increase in protein synthesis, since APC KRAS cells are trying to regulate their rates of protein synthesis via eIF2α signalling.
In chapter 5 I investigated changes in the metabolomes between APC and APC KRAS cells. I show that APC KRAS crypt cultures are highly dependent on glutamine for growth and upregulate many genes involved in glycolysis and glutaminolysis. I show that APC KRAS cells are metabolically flexible and also highlight the role the environment plays in metabolic phenotypes.
Overall, I have shown that intestinal epithelial cells with high-Wnt and high-MAPK signalling are sensitive to Wnt inhibition. I have also shown that these two signalling pathways cooperate to drive increased protein synthesis and deregulated metabolism to fuel proliferation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: R Medicine > RC Internal medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Supervisor's Name: Sansom, Professor Owen
• Date of Award: 2018
• Embargo Date: 14 June 2021
• Depositing User: Mr David Gay
• Unique ID: glathesis:2018-9089
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 May 2018 09:58
• Last Modified: 14 May 2021 06:44
• URI: https://theses.gla.ac.uk/id/eprint/9089