Specific estrogen receptor binding and biological effects of 16 alpha-iodoestradiol on human breast cancer cells.

16 alpha-Iodoestradiol was evaluated as an estrogen in MCF-7 and ZR-75-1 human breast cancer cells. 16 alpha-[125I]Iodoestradiol binds to equivalent numbers of specific estrogen receptors with a comparable binding affinity and similar sucrose density gradient behavior. 16 alpha-Iodoestradiol translocates receptor sites to the nucleus and induces a full range of estrogenic effects including thymidine incorporation, cell growth, and progesterone receptor. Because of its high specific activity, this compound may have unique applications on imaging of estrogen receptor-containing cells and specific receptor-mediated cytotoxicity.