Cellular Estrogen and Progesterone Receptors in Mammary Carcinoma

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Abstract
Cellular estrogen and progesterone receptors of human mammary cancer in cryostat-frozen sections were studied simultaneously. The receptor tracers used were a mixture of 17β-estradiol-6-carboxymethyl oxime-bovine serum albumin fluorescein isothiocyanate and llα-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 estrogenreceptor-positive epithelial cells, benign or malignant, of the mammary glands contain a significant number of progesteronereceptor 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.