Different adenosine triphosphatase (ATPase) activities were detected at an ultrastructural level in order to differentiate epithelial and myoepithelial cells in normal and neoplastic mouse mammary tissues. Mg2+-dependent and Na+-K+-dependent ATPase activities were studied in: BALB/c mouse mammary gland; a BALB/c carcinoma from a transplantable D2 hyperplastic nodule; a stable cell line, MCF-8, derived from the BALB/c carcinoma; and a BALB/c scirrhous-like carcinoma induced by MCF-8 cell inoculation. Mg2+-dependent ATPase was detected in the plasma membranes of the normal mouse mammary epithelial cells, the epithelial component of the BALB/c carcinoma, the MCF-8 cells in culture, and the atypical epithelial component of the scirrhous-like carcinoma. Na+-K+-dependent ATPase was not present in the plasma membranes of any of these mammary epithelial cells. Both Na+-K+-dependent and Mg2+-dependent ATPase were localized in the plasma membranes of the myoepithelial cells of the normal mammary gland and the BALB/c carcinoma. The results from these histochemical studies established that the cell of origin in both the BALB/c carcinoma and the scirrhous-like carcinoma was the mammary epithelial rather than the myoepithelial cells. Furthermore, these results indicated that the MCF-8 cell line was derived from the epithelial component of the primary BALB/c carcinoma. These conclusions, which were based on histochemical study, were supported by the presence of intracisternal type A viral particles in the epithelial cells of the primary BALB/c carcinoma, the MCF-8 cells in culture, and the epithelial cells of the scirrhous-like carcinoma. Thus, the enzymatic markers were specific for cell type and remained unchanged by the process of cell transformation.
This work was supported by an institutional Grant from the United Foundation of Greater Detroit.