Although not yet studied in BCa, metformin treatment was found to inhibit CXCL1 in head and neck squamous cell carcinoma (HNSCC) and esophageal squamous cell carcinoma (ESCC), suggesting a possible chemokine-mediated mechanism in metformin’s effect in BCa [213,214]. The gene discussed is CXCL1; the disease is esophageal squamous cell carcinoma.