Monoclonal antibodies as probes for estrogen receptor detection and characterization.

Splenic lymphocytes from a Lewis rat, immunized with purified estradiol-receptor complex of calf uterine nuclei, were fused with cells of three mouse myeloma lines to yield several monoclonal lines of hybridoma cells that secrete antiestrophilin antibodies, which, like the antiserum of the immunized rat, react specifically with estrophilin of calf tissues. In contrast, a Lewis rat, immunized with cytosol estradiol-receptor complex from MCF-7 human breast cancer cells after purification by a novel affinity chromatography technique, gave antiserum that crossreacts with receptor from mammalian as well as avian tissues. Monoclonal antibodies secreted by three hybridoma cell lines derived from this immunized rat showed interesting differences in cross reactivity. All recognized receptor from primate sources, two of the three monoclonal preparations recognized receptor from calf and rat uterus as well, but none reacted with estrophilin from hen oviduct. Thus, in addition to similarities, there appear to be immunocytochemical differences between estrogen receptors from mammalian and avian sources and between receptors from primate and non-primate tissues. These monoclonal antibody preparations, recognizing different determinants on the estrophilin molecule, provide a novel approach to the study of receptor structure and function as well as the basis for a simple immunoradiometric determination of estrogen receptors in human breast cancers. Preliminary studies indicate that they also may prove useful for the immunocytochemical detection of estrophilin in tissue sections.