Demonstration of vasculogenic mimicry in astrocytomas and effects of Endostar on U251 cells.

Angiogenesis is an important process for the cell growth of normal and tumor tissues. Vasculogenic mimicry (VM) is a newly described vascular network structure that was first described in aggressive melanomas. To find out whether VM also exists in astrocytomas and to examine its clinical significance, we studied 80 malignant astrocytoma samples using immunohistochemistry coupled with periodic acid-Schiff (PAS) staining. To explore the possible therapeutic methods of anti-VM formation, we cultured astrocytoma cells using three-dimensional Matrigel and investigated the effects of Endostar, an endothelial cell growth inhibitor, on astrocytoma cell growth, invasion, and VM formation. VM structures were found in 8 samples of malignant astrocytomas, seven of which were grade IV astrocytomas. Glioblastoma U251 cells cultured in Matrigel formed vessel-like loops and networks, mimicking the features of VM in vivo, whereas such structures were not found in cultured normal astrocytes or well-differentiated astrocytoma SHG44 cells. In addition, treatment with Endostar led to a dose- and time-dependent inhibition of proliferation and invasion of both U251and SHG44 cells, but VM formation by U251 cells in vitro was not prominently affected. In conclusion, VM is frequently detected in aggressive glioblastomas, and the presence of VM may constitute a new predictor for poor prognosis in astrocytoma patients. Although Endostar has broad anti-tumor effects due to anti-angiogenesis and anti-tumor cell mechanisms, its inhibitory effects on VM formation by U251cells in vitro are not remarkable.