CXCL12 and breast cancer: Ligand dependent GPCRs such as SDF‐1, thrombin, LPA, S1P, and endothelin receptors were found to have pivotal roles in many forms of tumors including prostate and breast cancer.61 Their downstream signaling cascades are transduced through G‐Alpha12 (GNA12) and G‐Alpha13 (GNA13) subunits constituting the subfamily of heterotrimeric G‐proteins.