Cell Organization and Responsiveness to Hormonesin Vitro: Genesis of Domes in Mammary Cell Cultures

Domes are multicellular structures generated from confluent monolayers of mammary epithelium under the influence of insulin and a corticosteroid hormone. The hemicyst structure and occurrence patterns of domes suggest an in vitro analogy to organized acini of mammary parenchyma. Two activities of dome cells, vegetative replication of the mammary tumor virus and synthesis of casein, suggest a functional analogy between domes and acini. The corticosteroid hormone is considered the primary hormonal stimulant for dome formation. Evidence is presented that RNA and protein synthesis is required for the corticosteroid effect, as are intact active transport functions of epithelial cells.