GRPR and breast cancer: GRPR functions through a G protein-coupled, 7-transmembrane receptor and is present at low levels in physiologically normal organs; however, it is often overexpressed in various malignancies, including PCa, lung cancer, breast cancer, colon cancer, ovarian cancer, pancreatic cancer, renal cell cancer, and various central nervous system (CNS)/neural tumors (Smith et al., 2005; Elshafae et al., 2016).