Inhibition of epidermal growth factor binding to cultured mouse epidermal cells by tumor promoters.

The tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA) caused partial inhibition of the binding of [125I]epidermal growth factor ([125I]EGF) to intact mouse epidermal cells (HEL/37). The proportion of [125I]EGF binding which was insensitive to TPA inhibition decreased with increasing EGF concentration. The partial inhibition of [125I]EGF binding was not due to destruction of TPA or to covalent linkage of EGF to receptor sites. The binding of [125I]EGF to HEL/37 cells showed a curvilinear Scatchard plot; this was converted into a linear plot in the presence of TPA. We conclude that TPA acts to inhibit interactions between EGF receptors or between EGF receptors and some other membrane component(s).