These CAAs then secrete chemokine C-C motif ligand 2 (CCL2), chemokine C-C motif ligand 5 (CCL5), IL-1β, IL-6, TNF-α, vascular endothelial growth factor (VEGF) and leptin, to promote the invasion and metastasis of BC cells [41,42,43,44]. The gene discussed is LEP; the disease is breast cancer.