In glioblastoma multiforme (GBM), cancer stem cells (CSCs) are thought to be responsible for gliomagenesis, resistance to treatment and recurrence. Despite increasing knowledge of the GBM biomolecular characterization and breakthrough in treatment, the prognosis in the great majority of patients is poor as almost all tumors recur in peritumor tissue. This site of alterations seems to harbor CSCs that show some differences when compared to CSCs derived from GBM. By means of immunocytochemistry, Western blotting and RT-PCR, we have compared CSCs derived from GBM (GCSCs) to those isolated from peritumor tissue (PCSCs) as to the expression of molecules linked to stemness (Nestin, Musashi-1, SOX2), proliferation and apoptosis (pERK1/2 and pJNKs), migration/invasion, angiogenesis, and hypoxia (reelin, GD3, NG2, VEGF, VEGFR1/2, HIF1α, and HIF2α). Furthermore, comparison of growth rate, frequency of tumor initiating cells (TICs), tumorigenicity in Scid/bg mice, and ultrastructure between the two CSC populations was performed. Finally, we analyzed the effect of different chemotherapeutic agents (temozolomide, etoposide, irinotecan and carboplatin) on proliferation of both GCSCs and PCSCs.
All the molecules analyzed were expressed in the two populations of CSCs. Among the investigated markers, nestin, pJNKs, Musashi-1, NG2 and VEGFR1 were found to be significantly increased in GCSCs if compared with PCSCs. Moreover, GCSCs grew at a higher rate and showed a greater frequency of TICs.
Animal survival time revealed that mice receiving GCSCs died significantly earlier than mice inoculated with PCSCs. Only PCSCs ultrastructure showed fully organized desmosomes and gap junctions. All the chemotherapeutic agents used inhibited proliferation of both GCSCs and PCSCs, although with different efficiency. Moreover, each drug had similar effect on the GCSCs and PCSCs derived from the same patient.
These findings support the need for a complete characterization of GCSCs and PCSCs to optimize treatment of GBM.
Supported by FIRB Accordi di Programma 2010
- CANCER STEM CELLS