ABSTRACT
The paper describes the characterization of six cell lines derived from breast cancers and maintained in long-term culture with regard to their responsiveness to oestrogens and anti-oestrogens. The authors focus on one of the cell lines (MCF-7) which is markedly stimulated by physiological concentrations of oestradiol as determined by effects of cell numbers and macromolecular synthesis. Higher concentrations of oestrogen are inhibitory and very high levels kill the cells. These latter effects appeared to be non-specific since they could also be observed with other steroids and in other cell lines which neither were sensitive to oestrogen nor contained specific oestrogen receptors. By contrast, the responsive cell lines contained receptors which bound oestradiol with high affinity; anti-oestrogens competed with oestradiol but had a lower affinity for the receptor. Anti-oestrogens also inhibited the growth of cells and blocked the stimulatory effects of oestrogen. At very high concentrations, anti-oestrogens could be cytotoxic. The authors suggest that the cell lines would prove to be valuable models by which to study hormone sensitivity in target tissues, most notably the effects of endocrine therapy in patients with breast cancer.
