Factors influencing the response of MCF-7 cells to an agonist of luteinising hormone-releasing hormone

To clarify the mechanism by which the luteinising hormone-releasing hormone agonist, buserelin, may have direct effects on breast cancer cells, factors potentially influencing its action have been studied in the MCF-7 breast cancer cell line. Oestradiol and epidermal growth factor (EGF), which stimulate the growth of MCF-7 cells in culture, reversed, at least in part, the inhibitory effects of buserelin. Insulin also abolished growth inhibition. Quantitative effects of buserelin differed according to the batch of fetal calf serum used as media supplement. These data suggest that the direct inhibitory effects of buserelin on breast cancer cells are mediated at least in part by an antagonism of growth-promoting factors.