Proliferative potential of vascular components in human glioblastoma multiforme

Sixteen patients with glioblastoma multiforme received a 1-h intravenous infusion of 5-bromo-deoxyuridine (BrdU), 150-200 mg/m2 at the start of surgery, to label S-phase cells in tumor tissue. Labeled cells of vascular components and of tumor parenchyma were detected in excised tumor specimens by indirect immunoperoxidase staining using anti-BrdU monoclonal antibodies followed by periodic acid-Schiff staining. The BrdU labeling index (LI, defined as the percentage of labeled cells in relation to the total number of cells scored) was calculated separately for vascular components and tumor parenchyma in each specimen. The BrdU LI of vascular components of glioblastoma multiforme was remarkably higher than that of normal brain (1.1%-8.7% vs. less than 0.05%). The mean BrdU LIs of vascular components and tumor cells in eight primary glioblastomas were 4.5 +/- 0.8% (mean +/- SE) and 9.9 +/- 1.1%, respectively, while the corresponding BrdU LIs in eight recurrent tumors were 2.7 +/- 0.5% and 9.3 +/- 0.7%. The differences in the BrdU LIs of primary and recurrent tumors were not statistically significant, but the BrdU LI of vascular components was consistently much lower than that of tumor cells. BrdU labeling of vascular components was inconsistent and occurred mostly in glomerular-shaped vessels, but only about 20% of them contained labeled cells. These results suggest that unusual vascular proliferation, such as the formation of glomerular-shaped vessels and endothelial or adventitial proliferation, in glioblastoma multiforme may have been programmed to slow down or even to cease at a certain stage, and is not likely to be the result of neoplastic transformation.