Regulation of EGFR and ERBB2 Expression by Estrogen Receptor in Breast Cancer
The epidermal growth factor receptor (EGFR/ERBB1) and the ERBB2 (HER2/neu) genes are both members of the type I family of growth factor receptors, and encode trans-membrane receptor tyrosine kinase proteins expressed on the epithelia of a number of tissues during mammalian embryogenesis. Thus, these proteins play key roles during development as demonstrated by the lack of viability of mice homologously deleted for either gene (1,2). However, expression of these genes in most adult tissues is much less marked, with the significant exception of certain solid tumors. The potential import of these findings lies in the fact that both genes can act as oncogenes in a variety of in vitro and in vivo assays (3,4). There is therefore a large literature documenting the incidence of overexpression of these proteins in a range of human carcinomas, including those from endocrine and nonendocrine tissues. For completeness, summarized below are the key features of expression of these genes in the normal breast and during tumorigenesis which are relevant to this chapter.
KeywordsEpidermal Growth Factor Receptor Expression Epidermal Growth Factor Receptor Gene ERBB2 Expression Epidermal Growth Factor Receptor mRNA ERBB2 Promoter
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