Cyclic AMP inhibits the growth of human breast cancer cells in defined medium

Three well-characterized human breast cancer cell lines, MCF-7, T47D and Cama-1, have been grown in defined medium in the absence of serum. Under these conditions, the growth of these cells was inhibited by a variety of cyclic AMP elevating agents, including cholera toxin, monobutyryl cyclic AMP, bromo-cyclic AMP, prostaglandin E2, and 1-methyl-3-isobutyryl xanthine. This inhibitory effect of cyclic AMP on breast cancer cells contrasts with the stimulation of proliferation induced by elevation of intra-cellular cyclic AMP in normal human mammary epithelial cells. Such a major perturbation of growth control may arise either as a result of malignant change, or may reflect a difference in the differentiation phenotype of normal and malignant human mammary epithelial cells in vitro.