Abstract
KRAS is the most frequently mutated oncogene in human cancer and plays a central, although poorly understood, role in colorectal cancer (CRC) progression. In this issue of Genes & Development, Boutin and colleagues (pp. 370-382) present a new mouse model of CRC in which the expression of oncogenic K-RAS is regulated by doxycycline. Using this model, they demonstrate that continued expression of oncogenic K-RAS is required for the survival of primary and metastatic colon cancers and that oncogenic K-RAS activates TGF-β signaling to promote tumor invasion and metastasis.