CXCR4 and melanoma: There are also reports of the following in melanoma: glutamate family of G protein-linked receptors (GRM1–8) [31,32], muscarinic receptor [33], selected GPCR ligands, signaling pathways including Frizzled (Fz) PAR1 parathyroid receptor1 (PTHR1) [34], and chemokine receptor (CXCR4) [35].