Generating mice with cancer is often time consuming and difficulty because of the need for genetic mutant mice. For this project, we deleted the Apc gene directly in the mouse colon using colonoscopy and the gene editing tool called CRISPR/Cas9. In this image, colon epithelial cells (those cells that are able to develop into tumors) are shown in green, while stromal cells (which cannot form colon tumors) are bright red. The colon tumor is yellow and arises from the epithelial cells (i.e., combination of red and green). This model is important because it allows us to directly and efficiently edit genes in the adult mouse colon. In the right image, the same tumor section is imaged with a nuclear stain (which is blue) instead of an epithelial stain (which is green in the left image).