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Quantitative differences in the effects of mouse and human epidermal growth factors on A431 human tumor cells
1Division of Nutrition and Endocrinology, Naylor Dana Institute for Disease Prevention, American Health Foundation, Valhalla, NY 10595.
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 X 10-9 M) and high affinity receptors (K(d) 2.7 X 10-10 M) are lower than those of hEGF (K(d) 1.2 X 10-9 M and 1.9 X 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%).
Insights
Human epidermal growth factor (hEGF) exhibits higher receptor affinity and greater cell growth stimulation than mouse epidermal growth factor (mEGF). This difference impacts radioreceptor assay accuracy for EGF-like proteins.
Area of Science:
- Cell biology
- Biochemistry
- Molecular biology
Background:
- Epidermal growth factor (EGF) plays a crucial role in cell growth and differentiation.
- EGF exerts its effects by binding to specific receptor sites on cell membranes.
- Differences in EGF species may influence receptor binding affinity and biological activity.
Purpose of the Study:
- To compare the receptor binding affinities of human epidermal growth factor (hEGF) and mouse epidermal growth factor (mEGF).
- To evaluate the effects of hEGF and mEGF on A431 cell growth.
- To assess the implications of differing affinities for radioreceptor assays.
Main Methods:
- Radioreceptor assays using A431 cell membranes to determine binding affinities (Kd) for hEGF and mEGF.
- Cell proliferation assays to measure the impact of hEGF and mEGF on A431 cell growth across various concentrations.
Main Results:
- Both hEGF and mEGF bind to two classes of receptor sites on A431 cells.
- mEGF shows lower affinities for both low and high-affinity receptors compared to hEGF.
- hEGF demonstrates a wider concentration range for stimulating cell growth and a higher maximal stimulating effect than mEGF.
Conclusions:
- hEGF has superior receptor binding affinity and a more pronounced growth-stimulating effect on A431 cells compared to mEGF.
- The lower affinity of mEGF can lead to inaccurate results in radioreceptor assays for human biological fluids.
- Understanding species-specific differences in EGF activity is critical for accurate biological assays and therapeutic applications.