GLIOMA INVASION IN-VITRO - REGULATION BY MATRIX METALLOPROTEASE-2 ANDPROTEIN-KINASE-C

A hallmark of invasive tumors is their ability to effect degradation o f the surrounding extracellular matrix (ECM) by the local production o f proteolytic enzymes, such as the matrix metalloproteases (MMPs), In this paper, we demonstrate that the invasion of human gliomas is media ted by a 72 kDa MMP, referred to as MMP-2, and provide further evidenc e that the activity of MMP-2 is regulated by protein kinase C (PKC). T he invasiveness of five human glioma cell lines (A172, U87, U118, U251 , U563) was assessed in an in vitro invasion assay and was found to co rrelate with the level of MMP-2 activity (r(2) = 0.95); in contrast, t he activity of this 72 kDa metalloprotease was barely detectable in no n-invasive control glial cells (non-transformed human astrocytes and o ligodendrocytes). Treatment with 1,10-phenanthroline, a metalloproteas e inhibitor, or with a synthetic dipeptide, containing a blocking sequ ence (ala-phe) specific for MMPs, resulted in a > 90% reduction in gli oma invasion. Furthermore, this MMP-2 activity could be inhibited by t he treatment of tumor cells with calphostin C, a specific inhibitor of PKC. Glioma cell lines treated with calphostin C demonstrated a dose- dependent decrease (IC50 = 30 nM) in tumor invasiveness with a concomi tant reduction in the activity of the MMP-2. Conversely, treatment of non-invasive control astrocytes with a PKC activator (phorbol ester) l ed to a corresponding increase in their invasiveness and metalloprotea se activity. These findings support the postulate that MMP-2 activity constit constitutes an important effector of human glioma invasion and that the regulation of this proteolytic activity can be modulated by PKC.