Culprit in Colon Cancer (IMAGE) University of Pennsylvania Caption Msi2 (stained red) is broadly expressed in intestinal tumors that result from loss of APC. Penn researchers believe activation of Msi2 downstream of APC loss drives metabolic activation of stem cells and blocks stem cell differentiation, leading to tumor growth. Credit University of Pennsylvania Usage Restrictions In context of reporting License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.