Cell receptors, including hormone receptors, are special proteins found within and on the surface of certain cells throughout the body, including breast cells. These receptor proteins are the “eyes” and “ears” of the cells, receiving messages from substances in the bloodstream and then telling the cells what to do. In other words, the receptors act like an on-off switch for a particular activity in the cell. If the right substance comes along that fits into the receptor — like a key fitting into a lock — the switch is turned on and a particular activity in the cell begins.
One type of receptor found in normal breast cells is the hormone receptor. By attaching to hormone receptors, estrogen and/or progesterone contribute to the growth and function of breast cells. Estrogen and progesterone are often called “female hormones” because they play an important role in women’s menstrual cycle, sexual development, pregnancy, and childbirth. Even after menopause, however, women continue to have these hormones in their bodies. Men have them, too, although in much smaller amounts than women.
Like healthy breast cells, most breast cancer cells — but not all — have hormone receptors and respond to the signals coming from these hormones. Knowing whether or not breast cancer cells have hormone receptors is an important piece of information for making treatment decisions. For hormone-receptor-positive breast cancer cells, hormonal therapy can be used to interrupt the influence of hormones on the cells’ growth and overall functioning. If you take the hormone away or block it, as these medications do, the cancer cells are less likely to survive.
It’s also worth noting that some breast cancers that are hormone-receptor-positive can lose their receptors over time. The opposite is also true: hormone-receptor-negative cancers can gain receptors. If the breast cancer recurs in the future as advanced disease, doctors should order a repeat biopsy and retest the cancer for hormone receptors. If the cancer cells no longer have receptors, hormonal therapy is unlikely to help treat the cancer. If the cells have gained hormone receptors, however, then hormonal therapy may be helpful. (See this Research News article for more information.)