ROLE OF EPITHELIAL GROWTH FACTOR IN MAMMARY GLAND DEVELOPMENT IN VITRO

Epithelial growth factor (EGF), a protein derived from mouse submaxillary gland, stimulates mammary epithelial cells in organ culture to initiate DNA synthesis and subsequently divide. The minimal effective concentration for this effect in vitro was approximately 8 × 10-10 M. Cells formed by EGF-mediated cell division in the presence of hydrocortisone undergo alveolar differentiation when stimulated post-mitotically by insulin and prolactin. Although the action of EGF in stimulating DNA synthesis resembles that of insulin, EGF lacks the activity of insulin to synergize with prolactin for the induction of milk proteins. These studies demonstrate that EGF can act as a potent growth factor for the regulation of mammary epithelial cell proliferation, and suggest that it may function as a hormone. © 1969.