More in particular, our overall approach to cancer research is to establish a parallel between the organization of normal tissues and that of tumor masses. In organs like the intestine, skin, and blood, highly dynamic processes take place where aged cells are continuously being replaced by new ones. Adult stem cells located within these tissues and organs are responsible for this critical turnover. Stem cells give rise to more specialized cells which are programmed to take care of specific functions (e.g. digest food and absorb nutrients; deliver oxygen to distant tissues; etc.) and to eventually die after a defined lag of time. Within these high turnover tissues a tightly controlled equilibrium is maintained so that new cells are generated to replace the dying ones. In order to maintain this equilibrium even in situations of stress (e.g. inflammation, wounding, etc.), stem cells are not alone. They are usually surrounded by other specialized cells which form a niche that insulates stem cells and mediates their response to external cues. This is of great relevance as upon tissue injury stem cells need to increase their production to balance cell loss in response to signals from the niche.