CXCR4 and prostate carcinoma: Key search terms included: “G protein-coupled receptor”, “GPCR”, “prostate cancer”, “prostate carcinoma”, “castration-resistant”, “orphan receptor”, “chemokine receptor”, “CXCR4′′, “CXCR7′′, “hormone receptor”, “GnRHR”, “therapeutic target”, and “drug discovery”.