Use of the dinitrophenyl hapten sandwich staining procedure (DHSS) to localize estrogen receptors in paraffin-embedded tissues.

To date, reliable and sensitive methods to localize the estrogen receptor (ER) in rat tissues and human breast cancers have required the use of frozen sections. This not only incurs poor tissue structure but also precludes the study of small breast lesions that are usually paraffin embedded for histological evaluation. We have developed and optimized a dinitrophenyl hapten sandwich staining (DHSS) immunocytochemical procedure to demonstrate ER in paraffin-embedded, hormone-sensitive tissues of the rat and in human breast cancers. The method was applicable to formalin- and Bouins-fixed material, with trypsinization of sections being essential. The immunocytochemical system utilized a dinitrophenyl (DNP) hapten-labeled monoclonal antibody to the receptor. Mouse IgM anti-DNP was used secondarily, followed by a DNP/peroxidase complex, diaminobenzidine/hydrogen peroxide chromogen, and silver intensification. This highly sensitive method localized the ER within paraffin-embedded rat uterus, fallopian tube, vagina, and normal and cancerous mammary gland. Furthermore, excellent staining was generated in human breast cancers in accordance with their ER-ICA status. Control sections involving simultaneous incubation with DNP-labeled and unlabeled H222 were background free, while uteri from castrated rats demonstrated reduced receptor immunostaining. Staining was also absent in ER-negative human breast tumors.