Karnoub et al. discovered that breast cancer cells stimulate the secretion of CCL5 and that paracrine CCL5 reversibly binds to C–C motif chemokine receptor 5 (CCR5) on the membrane surface of MDA-MB-231 cells to enhance the migration, invasion, and metastasis of breast cancer cells [16]. The gene discussed is CCL5; the disease is breast carcinoma.