Inflammatory bowel disease (IBD) is comprised of two main intestinal diseases: ulcerative colitis and Crohn’s disease. The major characteristic of IBD is chronic uncontrolled inflammation of the intestinal mucosa which can affect any part of the gastrointestinal tract. The link between inflammation and cancer is widely known and studied with those afflicted by chronic inflammatory conditions (such as IBD) more likely to develop cancer. Recently, mesenchymal stem cells (MSCs) have shown therapeutic potential in IBD; however whether MSCs promote or suppress tumour growth still remains contentious within the literature. A number of studies indicate that MSCs exert anti-tumour effects and suppress tumour growth whilst other studies report pro-tumour effects. The use of MSCs as a treatment for IBD has shown promise in both animal models and human trials. However, as MSC treatment is still novel the long term risks remain unknown. This thesis aims to uncover how the immune system is affected by colorectal cancer (CRC) in an inflammatory environment in vivo and also whether treatment with MSCs has an anti or pro-tumour effect in the same in vivo model.