The Role of Estrogen Receptors and Signaling Pathways in Breast Cancer

Abstract

Breast cancer is the leading cancer found in females today. Although breast cancer can be broken down into various subtypes, the most prominent type is hormone receptor (HR) breast cancer. Hormones especially effective in females, such as progesterone and estrogen, may stimulate cancer cell proliferation. The four main breast cancer subtypes are HR+/HER2-, HR-/HER2+/−, HR-/HER2+, and HR-/ HER2-, each characterized by the presence or absence of certain hormone receptors. HR breast cancers, due to high levels of progesterone and estrogen that promote cell proliferation and human epidermal growth factor receptors, grow by controlling gene transcription, cell division, and migration. Estrogen, a sex hormone primarily found in the female ovaries, binds to its associated receptors throughout the men- strual cycle and pregnancy. Various genes encode estrogen receptors, which regulate the expression of their respective genes. Estrogen causes ER-positive breast cancer growth via the continual binding of the hormone to cancer cell receptors. Conversely, ER-negative breast cancers are tumors that form due to the depletion of estrogen receptors from cancer cells. These cancers are regulated by two receptor types: ERα and ERβ. Recent treatment includes endocrine therapy, surgery, and epigenetic therapy.