Growth factor
Introduction
A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation, healing, and cellular differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.
Growth factors typically act as signaling molecules between cells. Examples are cytokines and hormones that bind to specific receptors on the surface of their target cells.
They often promote cell differentiation and maturation, which varies between growth factors. For example, Bone morphogenetic proteins (BMPs) induce bone and cartilage development. In contrast, epidermal growth factor (EGF) and fibroblast growth factors (FGFs) stimulate blood vessel formation (angiogenesis).
Types of Growth Factors
There are many types of growth factors, including:
- Platelet-derived growth factor (PDGF) - A potent stimulator of growth for connective tissue cells and certain types of blood cells.
- Vascular endothelial growth factor (VEGF) - Stimulates the growth of new blood vessels.
- Fibroblast growth factors (FGFs) - A family of growth factors involved in angiogenesis, wound healing, and embryonic development.
- Insulin-like growth factors (IGFs) - Regulate cell growth and development, especially in nerve cells.
- Nerve growth factor (NGF) - Stimulates nerve cell growth.
- Epidermal growth factor (EGF) - Stimulates cell growth and differentiation by binding to its receptor, EGFR.
- Transforming growth factor beta (TGF-β) - An important regulator of cell growth, proliferation, differentiation, and apoptosis.
Role in Cell Cycle
Growth factors play a crucial role in the cell cycle and have been shown to regulate cell division. The cell cycle is a series of events that take place in a cell leading to its division and duplication. Regulation of the cell cycle involves processes crucial to survival, including the detection and repair of genetic damage as well as the prevention of uncontrolled cell division.
The role of growth factors in the cell cycle has been studied in the context of cancer, where they often play a role in the uncontrolled proliferation of cells. Some growth factors can also induce cellular differentiation, which is the process by which a less specialized cell becomes a more specialized cell type. This is an essential process in early development, and growth factors like BMPs and FGFs play a crucial role.
Clinical Significance
Growth factors have been used in various clinical applications. For instance, they have been used in treating conditions like neutropenia and anemia. They have also been used in the treatment of tissue damage or loss, and in the field of tissue engineering.
In cancer, growth factors can stimulate the growth of cancer cells, and their inhibition can potentially be a therapeutic strategy. For example, the drug imatinib inhibits the receptor for a growth factor called PDGF, and is used in the treatment of chronic myelogenous leukemia.