MCF-7/S0.5 Human Breast Cancer Cell Line MCF-7/S0.5 is a tamoxifen-sensitive cell line established from the MCF-7 human breast cancer cell line by adaption to growth in low serum conditions.

Estrogen receptor-positive breast cancer is the most common type of breast cancer. About 80% of all breast cancers express the estrogen receptor (ER+) and depend on estrogen to support the growth and spread of the cancer cells. Hormonal therapy, such as tamoxifen, may help slow or stop the growth of ER+ breast cancers by blocking the actions of estrogen. Primary or acquired tamoxifen resistance poses a major clinical challenge in the treatment of ER+ breast cancer. The MCF-7/S0.5 is the parental line from which many tamoxifen-resistant cell lines have been derived and is utilized as a parental control to its derivative cell lines in parallel experiments.The presence of hormones in the serum required in tissue culture media complicates the demonstration of specific hormone and antihormone effects. The MCF-7/S0.5 human breast cancer cells have been adapted to long-term growth in low serum concentration (0.5% fetal bovine serum) by a stepwise reduction of the medium serum content from 5% to 0.5% FBS. MCF-7/S0.5 cells express both estrogen and progesterone receptors and are sensitive to tamoxifen.