Chapter 17 - Growth factors

Abstract

A large group of molecules are referred to and named using the term growth factor. These molecules have one or more of the following activities that lead to an altered growth rate of a particular cell type: (1) increasing cell mass by stimulating the production and/or inhibiting the degradation of macromolecules; (2) increasing cell number by stimulating the rate of cell division, referred to as mitogenic activity; (3) increasing cell number through increased cell survival due to the inhibition of apoptosis. Growth factors can have either positive or negative influences on these processes and their activities vary with cell type and the developmental stage of the organism. The activity of any one growth factor in a particular cell will be determined by its own state (active or latent); the presence of a receptor, and, in some cases, a coreceptor in the cell membrane; and the necessary signaling machinery inside the cell. In addition, the presence of other extracellular signaling molecules can impact the activity of a growth factor at a target cell. The goal of this chapter is to introduce five classes of growth factors with the emphasis on the structures of their members and the receptors that mediate their actions. Because of the great diversity of specific biological outcomes of the action of the growth factors on particular cells, no attempt is made to enumerate these. Rather the focus is on understanding the nature of the molecules engaged in these processes so that approaches to moderating their activities, particularly in the clinical setting of cancer, can be understood.