MMP2 and central nervous system cancer: Extracts of Viscum album are widely used as complementary medicine for cancer therapy, and recently some of the extracts such as aviscumine, iscador Qu, and ML-1 have been shown to regulate the expression of genes associated with the cell migration, invasion, adhesion, and even cell architecture formation in glioma cells by inhibiting TGF-β, SMAD2, and MMP-2/-9.