Cellular estrogen and progesterone receptors in mammary carcinoma

Cellular estrogen and progesterone receptors of human mammary cancer in cryostat-frozen sections were studied simultaneously. The receptor tracers used were a mixture of 17 beta-estradiol-6-carboxymethyl oxime-bovine serum albumin-fluorescein isothiocyanate and 11 alpha-hydroxyprogesterone hemisuccinate-bovine serum albumin-tetramethylrhodamine isothiocyanate conjugate. After incubation with the tracers, the estrogen-binding sites manifested apple-green, and the progesterone-binding sites manifested orange-red fluorescence when examined with a fluorescence microscope equipped with appropriate filters. The findings indicate that most estrogen-receptor-positive epithelial cells, benign or malignant, of the mammary glands contain a significant number of progesterone-receptor sites. Incorporation of a fluorescent progesterone conjugate into the histochemical reagent may help to confirm the existence of an operative receptor system in the cancer cells.