Glioblastoma-initiating cells from the peritumoral tissue have an invasive phenotype that is dependent on Rac and RhoA activation and downregulation of cytoplasmic p27.

The invasive nature of glioblastoma (GBM) represents a major clinical challenge contributing to poor outcomes. Invasion of GBM into healthy tissue restricts therapeutic access and surgical resection. Therefore, effective anti-invasive strategies of GBM cells can be key to increase the efficacy of chemotherapy against this devastating disease. As cancer stem or initiating cells are considered to retain the tumorigenic potential in a number of tumors including glioblastoma, we studied the invasion capabilities of glioblastoma initiating cells (GICs) that were isolated from the peritumoral (PT) tissue, which surrounds the tumor mass (TM) and remains in the brain after tumor removal. We found that PT-GICs are less proliferative but more invasive compared to TM-GICs. Gene expression arrays of cells derived from the tumor mass and the peritumoral tissue of three glioblastoma cases