epidermal growth factor

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epidermal growth factor (EGF) A small protein that acts as a cytokine and stimulates division of cells in the skin and connective tissue by binding to receptors (epidermal growth factor receptors) on the cell surfaces. It is formed by repeated cleavage of multiple EGF domains from a large EGF precursor protein anchored in the plasma membrane. EGF is commonly added to culture media to promote division of cultured mammalian cells. See also growth factor.