Immunohistochemical localization of prolactin-binding sites in R3327 rat prostatic cancer cells

Light microscope immunohistochemistry was used to test for and to localize prolactin-binding sites in the transplantable R3327 rat prostatic carcinoma. Fixed tissue sections of the tumor were first incubated with vehicle or varying concentrations of highly purified NIAMDD rat prolactin and then exposed to an immunoperoxidase staining sequence. Prolactin produced dose-related, immunospecific, staining in the cytoplasm of some neoplastic cells, indicative of intracellular prolactin-binding sites (IPBS). While cells with IPBS have been demonstrated in both differentiated and undifferentiated regions of this cancer, a role for prolactin in prostatic neoplasia, be it stimulatory or inhibitory, remains to be elucidated.