Definition

A gene that makes one of the two main types of estrogen receptor (ER) proteins. These proteins bind to and receive signals from the hormone estrogen. They are found inside the cells of female reproductive tissue, breast tissue, and many other types of tissue, and some cancer cells. Once activated by estrogen, ER proteins control the activity of certain genes that play an important role in cell growth and metabolism, sexual development, pregnancy, and other reproductive functions. Mutations (changes) in the ESR1 gene can cause the ER protein to be too active or found in higher-than-normal amounts on or in some types of cancer cells, such as breast or endometrial cancer cells. This may cause cancer cells to grow and spread. It may also make cancer cells not respond to certain anticancer drugs. The protein made by the ESR1 gene is a type of nuclear hormone receptor and a type of transcription factor.