Effect of hormones on growth fraction of human breast tissue in organ culture

Hormones are involved in the process of differentiation of the mammary gland. However, their effect on the growth of normal breast tissue is not completely understood. The purpose of the present study was to determine the growth fraction (GF) of the human breast tissue after 5 days in culture in the presence of 17β-estradiol, insulin and hydrocortisone. Normal human breast tissue was subjected to 3 different culture conditions: Group I was cultured for 1 hour with M199. Groups II and III were cultured for 5 days with media containing 5.0 μg/ml bovine pancreas insulin (I) and 1.0 μg/ml hydrocortisone (Hc); in addition, group III contained 0.05 μg/ml 17-estradiol (E). A continuous pulse of 2.5 μCi ³H-thymidine per ml was given for 5 days. The GF was determined as the percent of labeled cells out of the total number of cells available. For Group I the GF ranged from .04% to 0.29%. Groups II and III ranged from .16% to .55% and .16% to .62%, respectively. The F test for overall differences among the mean GF for the three groups was significant (F = 10.7; d.f. = 2.8; P < 0.006). There was a statistically significant increase in the mean GF between Groups I and II as well as between Groups I and III, with no significant difference between Groups II and III. It is concluded that insulin and hydrocortisone play a role in the growth of the human breast cells in culture, while 17 β-estradiol elicits a variable response. These hormones seem to stimulate the cells to reenter the cell cycle from G(o), since the GF was increased by insulin and hydrocortisone and in some samples by estrogen.