Growth factors in colorectal tumorigenesis

Colorectal tumorigenesis involves complex events including multiple genetic alterations in a well-known multistep mechanism called the adenoma-carcinoma sequence. Furthermore, growth and differentiation of normal and transformed cells are influenced by several growth factors, cytokines and hormones. Most of them, like Transforming Growth Factor alpha, Epidermal Growth Factor, Fibroplast Growth Factors, Insulin-like Growth Factors, and gastrin for instance have mitogenic effects. Transforming Growth Factor beta has however a key role in modulating these factors and has preferentially inhibitory growth effect. It is thought to play a strategic role in colorectal tumorigenesis although its mechanisms of action are complex and only partly understood. The aim of the present study is to review the effects of several growth factors, focusing on the role of TGF-beta in colorectal tumorigenesis.