Role of Membrane Estrogen Receptor (GPER1) on the Function of Immune Cells and Its Consequences on Breast Cancer Pathophysiology

Steroid hormones actively participate in the pathophysiology of breast cancer, because, among other factors, tumor cells have a deregulated expression of receptors for these hormones. Particularly, GPER1 is a G protein-coupled receptor that is responsible for the non-genomic signaling of 17β-estradiol (E2). GPER1 is known to be involved in the regulation of different systems, such as the nervous, reproductive, cardiovascular, and immune systems. However, the role of GPER1 in the pathophysiology of cancer, and particularly its effects on modulating components of the antitumoral immune response, have been underestimated to this date. Therefore, the present chapter offers an integral immune-endocrine vision in breast cancer by analyzing the current knowledge on the expression of GPER1 on different immune cells. We discuss the recent findings on these matters to have scope for the role of GPER1 on immune cells and its consequences on breast cancer development. We also propose how the use of antagonists for GPER1 could be useful as a complementary treatment for breast cancer patients.