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Expression of Differentiated Function by Mammary Carcinoma Cells in Vitro¹

Department of Medicine, Duke University Medical Center, Durham, North Carolina 27706, and the Division of Endocrinology, Veterans Administration Hospital, Durham, North Carolina 27705

Explants of C3H mouse and rat R323OAC mammary carcinomas were cultured in the presence of insulin, hydrocortisone, and prolactin in order to test the ability of these cells to differentiate into cells producing specialized cell products. Although normal epithelial cells differentiate into alveolar secretory cells which synthesize casein, -lactalbumin, and lactose synthetase A protein, C3H carcinoma cells fail to produce significant increases in these differentiated functions under the in vitro conditions. This failure is unrelated to rapid proliferation since the C3H carcinoma cells proliferate at a rate similar to that of normal cells and the rapidly proliferating R323OAC carcinoma cells can markedly increase casein synthesis in response to hormonal stimuli in vitro. The results support the concept that cells which form C3H tumors cannot limit the cell population size through the normal sequence of cell differentiation.

¹ This work was supported by USPHS Grant CA-10268 from the National Cancer Institute, NIH.

Received 3/ 6/69. Accepted 5/21/69.