Adenosine Triphosphatases as Histochemical Markers for the Cell of Origin in Experimental Mammary Carcinoma¹

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.