Growth rates of normal and abnormal human mammary epithelia in cell culture.

The in vitro growth rates of different classifications of human mammary epithelium were compared. Samples included 4 established breast cell lines and excised tissue or breast fluid cells originating WOMEN FOR 40 DIFFERENT AND comprising 3 classifications: normal, nonmalignant atypical, and malignant. Growth was quantitated in situ and expressed as population-doubling time. Principal findings were: (a) malignant cells divided at a slower mean rate than normal cells; (b) population-doubling time values of malignant cells were more heterogenous than those of normal cells; (c) cultures from nonmalignant atypias showed population-doubling time means and standard deviations between those of normal and malignant cells; and (d) long-term mammary tumor cell lines divided more slowly than did normal cells. Discussion includes implications of data for the preneoplastic state and cell culture of mammary epithelium.