Human serum and the growth of human mammary cells.

Human serum from a pool of normal donors, in the presence of fetal bovine serum, inhibited the growth of the major epithelial cell type observed in primary cultures established from biopsy samples of breast carcinoma. In contrast, the growth of cells from nonmalignant mammary tissues removed during reduction mammoplasty and from fibroadenoma was not inhibited. The replication of MCF-7 cells, an established line from a metastatic breast lesion, was also inhibited, whereas the growth of HBL-100 cells, originally derived from a presumably normal source of mammary tissue, was not inhibited by human serum in combination with fetal bovine serum. The growth of two additional cell lines, MDA 157 and MDA 231, was also not affected by human serum. Studies of growth in primary cultures were restricted primarily to direct microscopic observations of the number of cells per colony and the proportion labeled with [3H]thymidine. The results indicate the use of cell lines as adjuncts to primary cultures in future studies of this inhibitory activity.