Morphological expression of cell transformation induced by c-Ha-ras oncogene in human breast epithelial cells

The present work describes the morphological pattern of c-Ha-ras-transformed MCF-10A cells. This immortalized human breast epithelial cell line was transfected utilizing the calcium phosphate technique with pHo6 containing the neomycin-resistant gene alone, and identified as MCF-10Aneo, or with the normal Ha-ras proto-oncogene, MCF-10AneoN, or with the human p24 mutated Ha-ras oncogene, MCF-10AneoT cells. These three cell types were studied by scanning and transmission electron microscopy at passages 6 and 20 post-transfection. It was observed that transfection with the plasmid alone did not induce any morphological changes in MCF-10A cells. These two cell types exhibited those features that are characteristic of mammary epithelial cells in culture. Amplification of the normal c-Ha-ras oncogene by transfection induced significant morphological changes at the level of cell shape, from flat to cuboidal, and cytoplasmic changes suggesting a more metabolically active cell. These changes were made more prominent by transfection with the mutated ras oncogene, which induced stratification of a cuboidal epithelium and increase in cell size as well as a more pleomorphic nuclear and cytoplasmic appearance. Distinctive features induced by the mutated c-Ha-ras oncogene were the lengthening and thickening of cell surface microvilli, formation of blebs and emission of filopodial projections. It induced cytoplasmic changes consisting of formation of intracellular lumina, and increased the number of lysosomes, mitochondria and glycogen content, significantly decreasing the number of intermediate filaments. This is the first report that describes the morphological characteristics of a human breast epithelial cell line transformed in vitro.