GRP and breast cancer: Some GPCR ligands, such as bradykinin (BK), LPA, gastrin-releasing peptide (GRP), and bombesin (BN), activate EGFR and then induce stimulation in different types of tumors, such as prostate cancer, breast cancer, and pancreatic adenocarcinoma [44] Besides, studies have shown that leukocytes, including neutrophils, T cells, and dendritic cells, mainly perceive signals of movement, migration, chemotaxis, and localization through GPCRs and induce intracellular premigration response through the combination of agonists [45, 46].