Going mad with Smads.

In the past year, several studies of mice with genetically manipulated Smad genes have caught the attention of cancer researchers. Smad is a family of at least nine genes, each bearing an identifying number (e.g., Smad1, Smad2, and Smad9), and each encoding a protein involved in mediating cellular responses to transforming growth factor β (TGF-β) and related polypeptides. The prototype for this family of ligands was named “transforming growth factor” because it was initially identified as a serum component that stimulated neoplastic-like behavior in fibroblasts. Now we know that it has important roles in the life and death of . . .