Immunocytochemical and autoradiographic demonstration of prolactin binding to human breast cancer cells in tissue culture.

Specific binding of human prolactin to human breast cancer cells in culture was demonstrated for the first time by immunocytochemistry ad autoradiography. Using the former technique, it was found that prolactin binding to the cell surface was heterogeneous: some cells showing intense to moderate peroxidase reaction product and some cells showing absence of reaction product. After the cells were incubated with 125I-labeled prolactin and then embedded in plastic, autoradiography of sections revealed both surface-localized and intracellular silver grains, the latter suggesting internalization of prolactin. These two cytological techniques are useful for visualizing prolactin binding to human breast cancer cells and are applicable to studies on prolactin binding in human breast cancer.