PTK2 and central nervous system cancer: Reducing the survival rate of GBM8401 cells to 70% after treatment of caffeine at concentration of 1 mM (for 24 h)Reducing the survival rates of U-87MG and LN229 cells by 30% after 5 mM caffeine (for 24 h)Reducing the invasion of glioma cells through ROCK-cathepsin B/FAK/ERK signaling pathway after treatment with caffeine (0.1 mM and 0.5 mM) for 24 hDecreasing the mRNA, protein expression, and activity of cathepsin B