Growth of Preneoplastic Mammary Epithelial Cells in Serum-free Medium1

The conditions for growing preneoplastic mammary epithelial cells in primary cell cultures with serum-free factor-defined medium were established in a series of experiments. The cells, grown in Dulbecco's modified Eagle's medium with 0.6 mw Ca2+, epidermal growth factor, transferrin, insulin, and Na2SeO3, were fibroblast free, exhibited saturation densities similar to those of cells grown in serum-containing medium, and actively incorporated [3H]thymidine into DMA, as demon strated by biochemical and autoradiography assays. The total growth fraction over a seven-day experiment was 77%. Fetuin was sufficient as a serum substitute for attachment of cells to the dish, although it was apparently not necessary for contin ued growth of the cells. The possible benefits of growing preneoplastic mammary epithelial cells in serum-free factordefined medium are discussed.