Direct inhibitory effect of a luteinizing hormone-releasing hormone agonist on MCF-7 human breast cancer cells.

The effect of the LHRH agonist Buserelin on the MCF-7 human breast cancer cell line was studied. Cells were cultured in medium containing 10% untreated foetal calf serum or 10% steroid-depleted serum. In both media the DNA and protein content of cultures kept for 3-5 days in the presence of 80-800 nM Buserelin and 1 nM oestradiol were 8-27% lower than those of flasks cultured in the presence of oestradiol alone (P less than 0.05). LHRH itself (400 nM) also displayed an antiproliferative effect on the MCF-7 cultures. At an equimolar concentration, the LHRH antagonist ORG 30093D abolished the antiproliferative effect of Buserelin. MCF-7 cells did not specifically take up radioiodinated LHRH. Our data are the first to indicate that LHRH analogues may inhibit the growth of MCF-7 cells to a limited extent. The antitumour activity of these compounds in vivo may, then, be due to the main pituitary and gonadal effects, resulting in a decrease of the concentration of oestrogen in the circulation and, in addition, a direct effect at the target cell level.