Current understanding concerning intestinal stem cells

Figure 2 Relationship between intestinal stem cell genetic alterations and colorectal cancer development. Step1: Sequential mutations of APC, p53, Smad4 and Kras in ISCs; Step2: Normal ISCs are converted into CSCs; Step 3: By using the feeding from niche cells, CSCs expand their numbers along with producing daughter cells to form a solid tumor; Step 4: Upon escaping from their primary sites, some CSCs will systematically migrate into other organs to form metastatic lesions. ISCs: Intestinal stem cells.