Furthermore, Rao et al. investigated the pathophysiological role of GPR19 in metastatic breast cancer and found that adropin activates GPR19 via the mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 (MAPK/ERK1/2) pathway, resulting in phenotypic and functional changes, mainly with respect to changes in cell invasion [14]. Here, MAPK3 is linked to breast cancer.