MMP9 and breast carcinoma: A hypoxic environment in breast cancer can increase the levels of HIF-1α, VE-cadherin, MMP-9, Cdc42, EGFR, p-Akt, and p-mTOR to promote the development of VM via the HIF-1α/VE-cadherin/MMP-9, MMP-2 signaling pathway (48).