MMP9 and central nervous system cancer: Hyperactivation of Hh signaling in cancer cells themselves (i.e., Gli1 or Shh overexpression) has been shown to increase proangiogenic factor expression including vegfa [86,89,90], matrix metallopeptidase 2 (MMP2), matrix metallopeptidase 9 (MMP9) [86], and heparanase [91] in glioma cells or cysteine-rich angiogenic inducer 61 (Cyr61) in breast cancer cells [92].