Abstract
Currently, there are no generally accepted screening protocols for the discovery of asymptomatic brain tumors, particularly primary brain tumors. Therefore it would be desirable to develop novel, noninvasive biomarkers for the detection of brain tumors. Remodeling of the extracellular matrix and dysregulation of angiogenesis are process essential to the development and maintenance of many tumors. Matrix metalloproteinases (MMPs), a multigene family of degradative enzymes, have been implicated in the establishment and maintenance of the vasculature required for tumor progression and metastasis as well as in the initial angiogenic phase of tumor growth in experimental models and human tumors. In the central nervous system MMPs have been associated with brain tumor development. Studies of primary brain tumors reveal that MMP-2 and MMP-9, and several other MMPs are overexpressed in both experimental models and tissue samples from human patients. Furthemore, urinary levels of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) and their complex are elevated in patients with a variety of cancers, both organ confined and metastatic, both within and outside the urogenital tract. Given that (1) MMPs are present in brain tumors and (2) that urinary MMPs have shown utility as noninvasive biomarkers for non central nervous system cancer, we initiated this study to determine whether urinary MMPs might have potential as noninvasive biomarkers to detect the presence of brain tumors. In the present preliminary study, we determined the gelatinolytic activities in urine from patients with brain tumor (15 meningioma and 10 glioblastoma) and from and 20 healthy volunteers with no concomitant illnesses using gelatin zymography. The diagnosis of tumor was made using usual clinical and imaging criteria and confirmed by histopathological findings. First morning urine were collected from patients before surgical intervention. To investigate the gelatinolytic activity present in the concentrate urine, substrate gel zymography was performed. This method simultaneously identifies the entire panel of enzymes that are capable of degrading the specific substrate, and the activity is detected by a clear zone in the gel where the substrate (gelatin) has been digest by the enzyme. Gelatin zymography identified that MMPs were present in the urine of many patients with meningioma and glioblastoma, whereas only traces of MMP could be detected in the urine of healthy subjects with no evidence of disease. Five dominant proteinases were detected migrating at approximately 240, 220, 130 and 92 kDa (MMP-9) and 72 kDa (MMP-2). These preliminary results indicate that MMPs correlate with presence of disease. Other experiments are ongoing to verify whether these biomarkers decrease with treatment and can be tracked from source tissue to urine.