Quantitative differences in the effects of mouse and human epidermal growth factors on A431 human tumor cells

Abstract

Human and mouse epidermal growth factor (hEGF; mEGF) bind to the same two classes of receptor sites on cell membranes prepared from the human epidermoid carcinoma cell line A431. However, the affinities of mEGF for the low affinity receptors ( K d 3.5 × 10 −9 M) and high affinity receptors ( K d 2.7 × 10 −10 M) are lower than those of hEGF ( K d 1.2 × 10 −9 M and 1.9 × 10 −10 M respectively). In consequence, artefactually high results are obtained when mEGF is used for radioreceptor assays of EGF-like proteins in human biological fluids. Both species of EGF stimulated A431 cell growth at low concentrations and inhibited at high concentrations; however, hEGF enhanced cell growth over a wider concentration range (up to 1.6 nM), and had a higher maximal stimulating effect (38% vs. 25%).