Incorporation of alphafetoprotein by the MCF-7 human breast cancer cell line

The intracellular uptake of alphafetoprotein (AFP) and its fluorescein conjugates, by cultures of the MCF-7 human breast cancer cell line, has been demonstrated using an indirect immuno-peroxidase technique or by direct visualization under fluorescent lighting. The protein was localized in the cytoplasm. Ultrastructural autoradiographs of MCF-7 cells incubated with human 3H-AFP showed protein accumulation in several cytoplasmic organelles, particularly in lipid droplets. Nuclei were free of AFP. A significant species-specificity of AFP internalization was observed in comparative assays with human, mouse, pig and chicken AFP. The incorporation of the protein was prevented by incubation at 0 degrees C or by previous treatment of the cultures with 10nM sodium azide. Attention is paid to the reappearance in a human breast carcinoma cell line of a property associated during ontogenic development with ectodermal derivatives, including the epidermis.