GUCY2C and central nervous system cancer: Chlorotoxin or chlorotoxin-like peptides act as MMP2 inhibitors mainly by interacting with MMP2 on the extracellular side of the membrane, resulting not only in inhibition of MMP2 activity, but also the internalization of the MMP2 co-localized glioma-specific chloride channel (GCC) responsible for the change in chloride-specific current and anti-metastasis or antitumor effect without affecting normal cells [15,33].