MMP9 and central nervous system cancer: Taken together, these data suggest that psychological stress regulates CD147 expression though the β-AR-arrestin1-ERK-Sp1 pathway, which is activated by β- AR in the LN229 and U87cells line; this promotes the transport of lactic acid and the expression and secretion of MMP-2, MMP-9, and thereby augments the proliferation and invasion capabilities of glioma.