Definition of breast cancer resistance protein

breast cancer resistance protein (brest KAN-ser reh-ZIH-stunts PROH-teen): A protein that is involved in making cancer cells resistant (unable to respond) to anticancer drugs. Normally, breast cancer resistance protein works with other proteins to help move many different substances, including drugs and other chemicals, in and out of cells. It is found in stem cells and in normal tissues, including the intestine, liver, brain, and placenta. However, it may also be found in higher than normal amounts in some cancer cells, which can cause them to be unable to respond to certain anticancer drugs. Drugs that block breast cancer resistance protein are being studied in the treatment of some types of cancer. Breast cancer resistance protein was first identified in breast cancer cells. Also called BCRP.