Abstract

PIP: This article reviews the contribution of steroid hormone receptor studies to the resolution of a basic clinical problem: how to determine which cancers are hormone dependent without an actual treatment trial. Previously published studies on hormone receptor assays and analyses are reviewed, the current status of knowledge in the area is summarized in terms of its relevance to breast cancer cells, and future scenarios are proffered. Assay methods and available clinical results for cytoplasmic estrogen receptor identification in human breast cancer comprise the first section. Information on assaying nuclear estrogen receptor, and its relative clinical importance, is presented in Part 2. Assays to determine the presence of progesterone receptor in human breast cancer; the estogen regulation of such progesterone receptors; and clinical findings comprise Part 3. Studies of the mechanisms of estrogen action in the MCF-7 human breast cancer cell line are the subject of Part 4. Recent experiments in animals on the efficacy of antiestrogen treatments, such treatments in human in vitro cell cultures, and the few clinical trials available are presented in Part 5. It is emphasized that the simple presence or absence of estrogen receptors in tumors does not absolutely indicate whether growth of a particular tumor is sensitive to estrogens. Experimental appraoches, designed to further delineate this problem, are outlined, based on observations such as the finding that the probability of tumor regression correlates better with quantitative rather than with qualitative assessment of estrogen receptors; that the specific end product of hormone action is unknown and without this information an ideal biochemical marker to a tumor's sensitivity of hormones is unavailable; and that the complex sequence of biochemical events in the actions of estrogen needs more complete elucidation.