Intracellular proteins estrogen receptor

Fig. 7.3. A dot plot (on the left) showing the staining of cells from a human breast tumor for two intracellular proteins. Cytokeratin-positivity marks tumor cells in the suspension, and estrogen receptor positivity on these cells indicates superior prognosis. The plot on the right shows a correlation (in 27 breast tumors) between the intensity of estrogen receptor staining by flow cytometry and the level of estrogen receptor binding (by radioligand binding assay). Modified from Ian Brotherick et al. (1995).

The mechanisms of action of steroid hormones on lymphoid, mammary, and prostatic cancer have been partially clarified. Specific cell surface receptors have been identified for estrogen, progesterone, corticosteroids, and androgens in neoplastic cells in these tissues. As in normal cells, steroid hormones also form an intracellular steroid-receptor complex that ultimately binds directly to nuclear proteins associated with DNA to activate transcription of a broad range of cellular genes involved in cell growth and proliferation (see Chapter 39 Adrenocorticosteroids Adrenocortical Antagonists). 

Steroid hormones (e.g., cortisol and estrogen) are hydro-phobic and insoluble in water. These hormones circulate in plasma, reversibly bound to transport proteins (e.g., cortisol-binding globulin and sex-hormone binding globulin) with only a small fraction free or unbound available to exert physiological action.The half-life of steroid hormones is 30 to 90 minutes. Free steroid hormones, being hydrophobic, enter the cell by passive diffusion and bind with intracellular receptors either in the cytoplasm or the nucleus. ... 

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