Evaluating synergy between deregulation of the Wnt, PI3-Kinase and MAP-Kinase pathways in prostate tumourigenesis

The Wnt, PI3-Kinase (PI3K) and MAP-Kinase (MAPK) cell signalling pathways play important roles in human prostate cancer (PCa). In this thesis, analysis of a human PCa tissue micro-array (TMA) constructed by the Welsh Cancer Bank demonstrated upregulation of markers associated with these pathways in PCa. There was also greater expression of these markers in high-risk tumours with some being predictive of biochemical recurrence following surgery. Furthermore, there is evidence to support cross talk between these pathways allowing clustering into low- and high-risk samples based on expression profiles. Targeted next generation sequencing (NGS) also demonstrated recurrent mutations of genes associated with these pathways in PCa. Conditional transgenic mouse models were employed to explore the complex communication between these pathways. The loss of Pten was incorporated as a means of activating the PI3K pathway, and mutated β-catenin and K-Ras as means of aberrant Wnt and MAPK signalling. This study provides the first evidence of crosstalk and cooperation between these pathways, resulting in a significant effect on prostate tumourigenesis. Mice with loss of Pten in addition to activated mutations of β-catenin and K-Ras (Triple mutants) have significant upregulation of all three pathways resulting in a shorter survival compared to single and double mutants. The feasibility of these models allows further specific gene profiles to be induced in the mouse, providing a platform for pre-clinical testing of novel therapeutic agents. The effect of deregulation of these pathways on the cancer stem cell (CSC) population was explored using fluorescence-activated cell sorting (FACS) and organoid culture. Compound mutant (doubles and triple) tumours have a greater number of CSC or enriched cells compared to single mutant or wildtype (WT) mice. Compound mutant tumours had greater organoid forming efficiency than single mutants however this was significantly inferior to WT cells. Overcoming the difficulty experienced in cultivating tumour organoids will help manufacture targeted drugs with the aim of forming a cryopreserved organoid library to facilitate precision medicine