Open AccessGenistein and erbstatin inhibition of normal mammary epithelial cell proliferation is associated with EGF‐receptor down‐regulation
Author(s) -
McIntyre B. S.,
Sylvester P. W.
Publication year - 1998
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1046/j.1365-2184.1998.00108.x
Subject(s) - autophosphorylation , genistein , epidermal growth factor , tyrosine kinase , biology , endocrinology , cell growth , cell culture , tyrosine kinase inhibitor , medicine , receptor , signal transduction , microbiology and biotechnology , kinase , biochemistry , protein kinase a , genetics , cancer
Epidermal growth factor (EGF) is a potent mitogen for normal mouse mammary epithelial cells grown in primary culture. EGF activation of the EGF‐receptor (EGF‐R) induces intrinsic tyrosine kinase activity which results in EGF‐R autophosphorylation and tyrosine phosphorylation of other intracellular substrates involved in EGF‐R signal transduction. Genistein and erbstatin are anticancer agents which have been shown to be potent tyrosine kinase inhibitors. However, the effects of these compounds in modulating EGF‐dependent normal mammary epithelial cell proliferation is presently unknown. Therefore, studies were conducted to determine the effects of genistein and erbstatin on EGF‐dependent proliferation, and EGF‐R levels and autophosphorylation in normal mouse mammary epithelial cells grown in primary culture and maintained in serum‐free media. Chronic treatment with 6.25–100 μ M genistein or 1–16 μ M erbstatin significantly decreased EGF‐dependent mammary epithelial cell proliferation in a dose‐responsive manner. However, the highest doses of genistein (100 μ M ) and erbstatin (16 μ M ) were found to be cytotoxic. Additional studies showed that acute treatment with 6.25–400 μ M genistein did not affect EGF‐R levels or EGF‐induced EGF‐R autophosphorylation, while acute treatment with 1–64 μ M erbstatin caused a slight reduction in EGF‐R levels, but had no effect on EGF‐dependent EGF‐R autophosphorylation in these cells. In contrast, chronic treatment with similar doses of genistein or erbstatin resulted in a large dose‐responsive decrease in EGF‐R levels, and a corresponding decrease in total cellular EGF‐R autophosphorylation intensity. These results demonstrate that the inhibitory effects of chronic genistein and erbstatin treatment on EGF‐dependent mammary epithelial cell proliferation is not due to a direct inhibition of EGF‐R tyrosine kinase activity, but results primarily from a down‐regulation in EGF‐R levels and subsequent decrease in mammary epithelial cell mitogenic‐responsiveness to EGF stimulation.