MMP2 and glioblastoma: The specific surface receptor for CLTX on GBM cells has not been identified, however, the expression of matrix metalloproteinase 2 (MMP2), chloride channel CLCN3, and phospholipid protein annexin A2 (ANXA2) all appear to be required for CLTX binding to GBM cells (Soroceanu et al., 1998; Deshane et al., 2003; McFerrin and Sontheimer, 2006; Tatenhorst et al., 2006).