Immunohistochemical Detection of an Estrogen-regulated Protein by Monoclonal Antibodies¹

It has been shown previously that estradiol regulates the synthesis of a M_r 24,000 cytosol protein in MCF-7 human breast cancer cells. This protein is an attractive probe to study the mechanisms of estrogen regulation in human breast cancer. We have produced monoclonal antibodies against the M_r 24,000 protein which show immunocytochemical localization in the cytoplasm of MCF-7 cells grown as solid tumors in nude mice. They do not react with normal mouse tissue or with MDA-MB- 231 cells, an estrogen receptor-negative cell line. Moreover, the monoclonal antibodies react against certain human breast tumor biopsy samples. These data suggest that the monoclonal antibodies obtained will be useful to detect the estrogen-regulated protein by immunohistochemistry.