MMP9 and cancer: The relative quantification results showed that tumor cells transfected with CD133+ significantly up-regulated the protein and mRNA levels of VE-cadherin, MMP-2 and MMP-9, compared to those in CD133− and control groups (Figure 5C, 5D), indicating that CD133+ cancer cells might facilitate the expression of VE-cadherin, MMP-2 and MMP-9, and enhanced VM-like channel formation.