The Bert Vogelstein Laboratory seeks to develop new approaches to the prevention or treatment of cancers through a better understanding of the genes and pathways underlying their pathogenesis. Our major focus is on cancers of the colon and rectum. We have shown that each colon neoplasm arises from a clonal expansion of one transformed cell. This expansion gives rise to a small benign colon tumor (called a polyp or adenoma). This clonal expansion and subsequent growth of the tumors appears to be caused by mutations in oncogenes and tumor suppressor genes, and the whole process is accelerated by defects in genes required for maintaining genetic instability. Mutations in four or five such genes are required for a malignant tumor to form, while fewer mutations suffice for benign tumorigenesis. As the mutations accumulate, the tumors become progressively more dangerous. Current studies are aimed at the further characterization of the mechanisms through which these genes act, the identification of other genes that play a role in this tumor type, and the application of this knowledge to patient management.