Abstract: A mouse model is provided which is directed to mice bred to have a disruption in the TGF-? signaling pathways which causes tumorigenesis in the liver and gut of the developing mice. The mice models of the invention include those mice whose genome include at least one mutant allele of a protein involved in the TGF-? signaling pathway, such as the elf protein or to the Smad proteins, and such models are advantageous in that they allow the study of tumor suppression and development in the liver and gut and can thus be used to study, assess and treat a variety of forms of hepatocellular and gastrointestinal cancer. Use of the Elf and Smad proteins and antibodies thereto in the diagnosis and treatment of liver and gut tumors is also provided.