any of various chemicals, particularly polypeptides, that have a variety of important roles in the stimulation of new cell growth and cell maintenance. They bind to the cell surface on receptors and are potential targets for anticancer therapy (see epidermal growth factor receptor). Specific growth factors can cause new cell proliferation (e.g. *transforming growth factor, epidermal growth factor, haemopoietic growth factor) and the migration of cells (fibroblast growth factor) and play a role in wound healing (platelet-derived growth factor; PDGF). Some growth factors act in the embryonic stage of development; for example, *nerve growth factor. Some growth factors that induce cell proliferation are involved in the abnormal regulation of growth seen in cancer when produced in excessive amounts (e.g. insulin-like growth factor, IGF-I). Growth factors produced locally around a carcinoma (e.g. *vascular endothelial growth factor) are important in the encouragement of invasion by the tumour; other factors (e.g. autocrine motility factor, migration-stimulating factor) are also significant. See also bone growth factors.... growth factor
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