Immunoreactive prolactin in epithelial cells of normal and cancerous human breast and prostate detected by the unlabeled antibody peroxidase-antiperoxidase method.

A rabbit antiserum to ovine prolactin was used with the peroxidase-antiperoxidase method to search for immunoreactive prolactin in normal and pathological human breast and prostate. We first substantiated that the heterologous antiserum could recognize human prolactin. When sections of human anterior pituitary were exposed to the anti-prolactin serum, groups of angular-shaped cells were selectively stained. The immunostaining of pituitary cells appeared specific for prolactin since both ovine and human prolactin abolished immunostain ing when they were added to the anti-prolactin serum. In contrast, human growth hormone and human chorionic gonadotropin did not eliminate immunostaining. Using this anti-pro lactin serum that was capable of selective recognition of prolactin-containing cells in human tissue, we stained sections of normal breast (five cases) and normal prostate (three cases). Numerous epithelial cells in these tissues were immunostained by the antiserum. The immunostaining was abolished by dele tion of the prolactin antiserum and also by use of prolactin antiserum absorbed previously with human prolactin rather than the heterologous antiserum alone. Immunostaining was not eliminated by absorption of antiserum with human growth hormone or human chorionic gonadotropin. These results sug gested that the immunostaining of normal breast and prostate was related to the presence of immunoreactive prolactin in epithelial cells of these organs. In prostate, immunostaining was confined to the secretory cell population; the basal cells were not stained with anti-prolactin serum. In breast, immuno staining did not appear to be confined to secretory cells but seemed to occur throughout the breast parenchyma. The im munostaining of normal breast epithelium was markedly het erogeneous with cells lacking immunoreactivity intermixed with cells having positive reactivity. This was less pronounced in normal prostate epithelium where most secretory epithelial cells were immunostained. However, marked variation in stain ing intensity between acini was commonly observed in normal prostate. Sixty-four % (14 of 22) of the primary prostate adenocarcinomas which were examined showed strong staining reactions with anti-prolactin serum. Two of three metastatic tumors of prostate origin had similar strong staining reactions. Most primary tumors of the prostate with strong staining reactions were poorly differentiated infiltrating adenocarcinomas (11 of 14; 79%). By contrast, 25% (three of 12) of the well-differen' Supported by Research Grant CA 15798 from the National Prostatic Cancer Project, National Cancer Institute, and Contract NO1-CP-43237. National Cancer Institute. 2 To whom requests for reprints should be addressed. 1American Cancer Society Professor of Clinical Oncology. Received April 3, 1981 ; accepted March 2, 1982. tiated prostate adenocarcinomas and 11 % (one of nine) of the benign prostate hyperplasias which were tested showed strong staining reactions when treated with anti-prolactin serum. Seven of 12 (58%) infiltrating duct carcinomas of the breast were strongly stained with anti-prolactin serum, but most breast fibroadenomas were not stained (six of eight; 75%). None of seven adenocarcinomas of the colon tested as controls were stained by anti-prolactin serum. As was the case with normal breast and prostate, absorption of anti-prolactin serum with human prolactin but not human growth hormone or human chorionic gonadotropin abolished the immunostaining of malig nant breast and prostate. These results suggested that the immunostaining of breast and prostate carcinomas was related to immunoreactive prolactin. The results reported here empha size the value of the peroxidase-antiperoxidase method in the study of hormone target organ interactions as well as in retro spective studies of pathological materials.