During prostate cancer metastasis, a CXCL12-rich niche is reported to facilitate colonization at a secondary site (particularly in the bone) and CXCR4-CXCL12 signaling plays a key role in mediating tumor–stroma interactions required for prostate cancer cells to grow in the presence of chemotherapeutic agents [189,284,287]. This evidence concerns the gene CXCR4 and prostate carcinoma.