Fine structure of a murine mammary carcinoma cell line.

A fine structural study was made of cells from the epithelioid MCF-8/5-2A cell line derived from a MuMTV-free D2 transplantable hyperplastic outgrowth. Electron microscopy shows the cells to be truly epithelial with many cell-to-cell junctions and microvilli. The cells are similar in many respects to normal mouse mammary gland and some of the conventional mammary tumor derived cell lines. This study supports previous observations of the absence of MuMTV in MCF-8 within the limits of morphological detection, and demonstrates the presence of numerous virus particles within, or budding into, cisternae of the endoplasmic reticulum and nuclear envelope. These intracisternal A particles have not been previously described in such abundance in mammary tumor tissue culture cells.