STAT5B and breast cancer: Employing in vitro HUVEC tube formation or in vivo orthotopic mouse model, and gene editing or specific small inhibitors strategy, and utilizing qPCR, western blot, ELISA, or immunofluorescent/immunohistochemistry staining methods, we found the following: 1) PFKFB4 upregulates IL-6 expression via NF-κB signaling in breast cancer cells; 2) PFKFB4-induced lactate secretion contributes to NF-κB activation in breast cancer cells; 3) IL-6 elicits angiogenesis via STAT5A/P-STAT5 in HUVEC; 4) 5-MPN (a specific PFKFB4 inhibitor) suppresses angiogenesis in vitro and in vivo.