Effect of hormones on growth rates of malignant and nonmalignant human mammary epithelia in cell culture.

The individual effects of seven hormones on the in vitro growth rate of different classifications of human mammary epithelium were compared. Hormones used were: 17 beta-estradiol, estriol, progesterone, hydrocortisone, testosterone, prolactin, and growth hormone. Cell cultures included three established breast cell lines and primary monolayer cultures established from breast fluids and excised mammary tissue from 40 women and 4 men. Specimens comprised three classifications: normal, nonmalignant atypical, and malignant. Growth was quantitated in situ and expressed as population doubling time. Principal findings were: (a) estrogens, prolactin,.and growth hormone stimulated growth of normal cells more frequently than growth of malignant cells, whereas testosterone and hydrocortisone stimulated growth of malignant cells more frequently than growth of normal cells; (b) cells cultured from nonmalignant atypias generally showed hormone response profiles intermediate between those of normal and malignant cells; (c) progesterone stimulated the growth of cells from malignant specimens but not the growth of cells from normal and nonmalignant atypical samples.