Human brain glioma stem cells are more invasive than their differentiated progeny cells in vitro

Glioma, the most commonly occurring primary intracranial tumor, remains associated with a dismal outcome, despite the availability of multimodal therapies. Recently, however, the identification of brain glioma stem cells (BGSC) has opened up new avenues for research. BGSC are now accepted as the progenitor cells of gliomas and are thought to determine the biological features of the resulting tumors. Thus, the diffuse invasiveness of gliomas should also be theoretically driven by BGSC. However, little research effort has been directed at understanding the invasiveness of BGSC. In the present study, BGSC from eight surgical glioma specimens were cultured and identified. Using Matrigel invasion assays, the invasiveness of these cells was measured and compared with that of their respective differentiated progeny cells in vitro. For all eight clinical specimens, the BGSC were significantly more invasive than their differentiated progeny cells. These findings indicate a key role for BGSC in glioma infiltration and invasion. We also found that BGSC tended to aggregate and reform into new spheres after travelling into the Matrigel, preserving some of the morphological characteristics of the suspended cells. The invasiveness of the BGSC did not correlate with the pathological grade of glioma in the present study, so further investigations using larger sample sizes are needed to better understand the mechanisms underlying the invasiveness of BGSC.