MMP9 and central nervous system cancer: The invasiveness of U251 cells decreased following COL17A1 reduction compared to cells transfected with non-targeting siRNA (P<0.01) (Figure 3A), and MMP9 expression was significantly reduced after knocking down COL17A1 (P<0.01) (Figure 3E), while COL17A1 knockdown had little effects on the rate of migration in U251 glioma cell lines.