Professor Simon Leedham is a Wellcome Senior Research Fellow in Clinical Science and an Honorary Consultant Gastroenterologist
Outline of Research
Adult gastrointestinal stem cells are the targets of carcinogenic gene mutations and are believed to be the cells of origin of luminal gastrointestinal cancers. Our published work has examined the clonality and genetic mutation burden of pre-neoplastic gastrointestinal disease. Our current research focuses on the homeostatic cell-signaling pathways that control intestinal stem cells and the dysregulation of these pathways in carcinogenesis. The wnt pathway is the best characterised system and promotes the maintenance and proliferation of stem cells, however other signaling pathways such as the Bone Morphogenetic Protein (BMP) and Notch pathway cross-talk and interact with wnt signaling. Recent work from our laboratory on hereditary polyposis syndromes and genome-wide association studies in sporadic colorectal cancer patients has implicated the BMP pathway’s involvement in predisposition to colorectal cancer.
Projects in the lab
Clonality and clonal ordering.
We have developed techniques for examining the mutation burden of single intestinal crypts from archival paraffin embedded tissue. We use individual crypt mutation burden to analyse clonal evolution and construct tumor phylogeny by examining the spatial distribution of shared mutations in different phenotypic regions across single lesions; a technique that has been termed clonal ordering or genetic dependency analysis
‘Just-right’ wnt signal levels and regional intestinal tumour formation.
Mutations in the tumour suppressor gene APC result in increased canonical wnt signaling in intestinal stem cells and are found in up to 85% of colorectal tumours. The ‘just-right’ hypothesis predicts that an optimal but not excessive level of wnt signal in necessary for tumourigenesis and it is this that determines the APC mutation spectra. The optimal level of wnt signal varies throughout the intestinal tract. We are investigating the underlying basal wnt gradient in the human and mouse and have used transgenic mouse models to examine the effect of pan-intestinal wnt perturbation.
Mesenchymal control of intestinal stem cells.
There is increasing evidence to suggest that the epithelial stroma significantly influences tumour development and progression. BMP pathway constituents are mesenchymally expressed and act in a paracrine fashion upon the intestinal epithelium, antagonising wnt signaling and promoting differentiation in mature enterocytes. We are examining the epigenetic and transcriptional control of BMP pathway constituents and functionally characterizing the role of this pathway in intestinal stem cell control in vitro using colorectal cancer and myofibroblast cell lines and in vivo by developing transgenic animal models.
Intestine, Heal Thyself! Regulating the Intestinal Epithelial Response to Injury.
Leedham SJ., (2020), Cellular and molecular gastroenterology and hepatology
Remission of Inflammatory Bowel Disease in Glucose-6-Phosphatase 3 Deficiency by Allogeneic Haematopoietic Stem Cell Transplantation
Bolton C. et al, (2020), Journal of Crohn's and Colitis, 14, 142 - 147
Deciphering the molecular signalling underpinning early-dissemination and metastasis from stage I colorectal cancer
Dunne P. et al, (2019), BRITISH JOURNAL OF CANCER, 121, 4 - 4
Exploiting differential Wnt target gene expression to generate a molecular biomarker for colorectal cancer stratification
Kleeman SO. et al, (2019), Gut
The polymorphic variant rs1800734 influences methylation acquisition and allele-specific TFAP4 binding in the MLH1 promoter leading to differential mRNA expression.
Thomas R. et al, (2019), Scientific reports, 9