Abstract
The hormone-dependent nature of some human breast cancers has been appreciated by physicians for nearly a century.(1) Clinical responses in breast cancer patients to ablative and additive hormone therapies suggest that several hormones are important growth regulators of mammary cancer. Recent studies of the basic mechanisms by which hormones influence target tissues have led to important advances in our understanding of steroid hormone action and the clinical care of women with breast cancer.(2,3) It is now recognized that the first step in steroid hormone action is the binding of the hormone to a cytoplasmic receptor protein.(4) In the absence of this receptor, the steroid hormone is unable to elicit a response in the cell. Using this principle, investigators have now identified receptors for estrogen and other steroid hormones in some breast tumor samples, providing a basis for more rational therapeutic decisions.