Abstract
High grade gliomas invariably recur due in a large part to tumor cells permeating normal brain in an inaccessible, diffuse manner. Previous work demonstrates that the expression of matrix metalloproteinases (MMP) contributes to this characteristic. Not only can MMPs assist a cell in traversing its environment by clearing extracellular matrix molecules, but they can also impact non-traditional downstream signals that affect a cell's ability to interact and respond to its surroundings. Contributions to the induction of MMP expression and functional significance in glioma are still under investigation. Evidence in other cancer settings indicates that nitric oxide (NO) may play a role in tumor/cell progression that can influence MMP production. Matrix metalloproteinase-1 (MMP-1), also known as interstitial collagenase, and the constitutive nitric oxide synthases (NOS) have been shown to be over-expressed in high grade gliomas. In the current study we investigated the potential involvements of NO with regard to MMP-1 and functional glioma cell movement. With the treatment of the NO donor sodium nitroprusside (SNP), there was significant induction of MMP-1 mRNA, secreted MMP-1 protein and motility of glioma cell lines within 48 h. RNA inhibition of MMP-1 through transient transfection of three MMP-1 specific siRNAs revealed a marked abrogation of the NO-mediated induction of motility. In addition, application of the NOS inhibitor N(omega)-Nitro-L-arginine methyl ester (L-NAME) impaired movement of glioma cells. These data provide evidence for a regulatory axis of high grade glioma cell movement from NO through MMP-1, with NOS inhibitor results showing promise for future pharmacologic investigation.