Autoradiographic localization of glycoprotein in human breast cancer cells maintained in organ culture after incubation with (3H)fucose or (3H)glucosamine

Abstract

Explants of nine infiltrating duct carcinomas of the human female breast, maintained in organ culture, were exposed to the glycoprotein precursors, L-[3H]furcose and [3H]glucosamine, in order to determine the cellular distribution of newly synthesized glycoprotein as revealed by autoradiography with the light and electron microscopes. Explants were incubated with a single isotope for 2 hr, at which time some of the labeled explants were removed for autoradiographic analysis while the rest were transferred to nonradioactive medium for an additional 24 hr. After exposure to label for 24 hr, autoradiography with each isotope was similar and showed strong reactions over most tumor cells. The reactions were due to clumps of silver grains over intracytoplasmic lumina within single tumor cells and silver grains over Golgi saccules, cytoplasmic vesicles, lysosome-like bodies, lateral and basal plasma membranes, and microvilli. Extracellular ductular structures were also heavily labeled. At the later sampling time, Golgi saccules often showed a reduced reaction while the reactions over other organelles and intracellular and extracellular ductular structures remained strong. The observations suggest that in our in vitro system the tumor cells are metabolically active and complete the synthesis of the carbohydrate side chains of glycoproteins within the Golgi apparatus. From there, some of the newly synthesized glycoprotein appears to migrate to plasma membranes and lysosome-like bodies. Furthermore, our data support the notion that many duct carcinomas of the breast exhibit secretory activity by showing that some newly synthesized glycoprotein also appears to become products that are secreted into intracellular and extracellular ductular structures.