No abstract

No abstract

No abstract

No abstract

No abstract

A medium consisting of a rich basal nutrient mixture supplemented with bovine insulin (10 ,ug/ml), human transferrin (10 [Lg/ml), human cold-insoluble globulin (5 jAg/ml), and ethanolamine (0 .5 mM) supported the growth of the A431 human epidermoid cell line in the absence of serum with a generation time equal to that of cells in serum-containing medium .Addition of epidermal growth factor (EGF) to this culture medium at concentrations mitogenic for other cell types resulted in a marked inhibition of A431 cell growth . Inhibitory effects of EGF were observed at 1 ng/ml and near-maximal effects were observed at 10 ng/ml . The inhibitory effect of EGF could be reversed by the omission of EGF in subsequent medium changes and could be prevented by the addition of anti-EGF antibody to the culture medium . Inhibition of A431 cell growth by EGF also could be demonstrated in serum-containing medium .Epidermal growth factor (EGF), a polypeptide originally isolated from mouse submaxillary gland by Cohen (see reference 1), is a potent mitogen for a number of cell types in culture or in vivo . The A431 human epidermoid carcinoma cell line has been used in recent years as a model for the study of early events after the interaction of EGF with its specific cell surface receptor . These cells express an unusually large number of high affinity cell membrane receptors for EGF (2, 3) and have been used to demonstrate internalization of EGF by whole cells (3-6) and enhancement of protein phosphorylation in membrane preparations treated with EGF (7-11) . These cells also have been used in experiments designed to identify and isolate the EGF receptor (12)(13)(14), and in studies of rapid effects of EGF on cell morphology (15, 16) and pinocytotic activity (17) . Although the A431 cell line is clearly an attractive model system for the study of EGF effects, no data have been reported regarding the mitogenic potential of EGF for these cells, and indications were that experiments designed to demonstrate stimulation of cell growth upon the addition of EGF to A431 cells under common culture conditions had been unsuccessful 11) . Recent work from the laboratories of Sato and others (18, 19, and references cited therein) has established that for many cell types it is possible to replace the usual serum supplement in culture medium with specific combinations of nutrients, hormones, and growth factors, binding proteins, and attachment factors, and that the biological effects of hormones or growth factors often may be better identified in such serumfree media than in serum-containing media. Using this ap-

Mouse embryo cells cultured in vitro in serum-supplemented media undergo growth crisis, resulting in the loss of genomically normal cells prior to the appearance of established, aneuploid cell lines. Mouse embryo cells established and maintained for multiple passages in the absence of serum did not exhibit growth crisis or gross chromosomal aberration. Cells cultured under these conditions were dependent on epidermal growth factor for survival. Proliferation was reversibly inhibited by serum or platelet-free plasma, suggesting that mouse embryo cultures maintained by conventional procedures are under the influence of inhibitory factors.

No abstract