The excessive activation of mitogenic signaling cascades that are modulated by these overexpressed ligands and receptors is compounded by the presence of mutations in the K-ras oncogene. Pancreatic cancers also overexpress transforming growth factor betas (TGF-βs) that usually inhibit the growth of epithelial cells. Pancreatic cancers, however, underexpress the type I TGF- βreceptor and harbor mutations in the smad4 gene, alterations that prevent TGF-ßs from inhibiting cancer cell growth but that do not confer onto pancreatic actions that promote cancer growth in vivo. Read more . . .