Targeting of replicating CD133 and OCT4/SOX2 expressing glioma stem cells selects a cell population that reinitiates tumors upon release of therapeutic pressure

The existence of radio- and chemotherapy-surviving cancer stem cells is currently believed to explain the inefficacy of anti-glioblastoma (GBM) therapies. The aim of this study was to determine if a therapeutic strategy specifically targeting GBM stem cells (GSC) would completely eradicate a GBM tumor. In both the in vitro and the in vivo models, ganciclovir therapy targeting proliferating GSC promotes the survival of a quiescent, stem-like cell pool capable of reproducing the tumor upon release of the therapeutic pressure. Images of small niches of therapy-surviving tumor cells show organized networks of vascular-like structures formed by tumor cells expressing CD133 or OCT4/SOX2. These results prompted the investigation of tumor cells differentiated to endothelial and pericytic lineages as a potential reservoir of tumor-initiating capacity. Isolated tumor cells with pericyte and endothelial cell lineage characteristics, grown under tumorsphere forming conditions and were able to reproduce tumors after implantation in mice.