PROM1 and glioblastoma: The discovery of a rare, highly tumorigenic, self-renewing sub-population of glioblastoma multiforme (GBM) cells that express the cell surface marker cluster of differentiation (CD) 133 (see [14,15]), the so-called GBM stem cell population, suggests that therapeutic approaches that effectively inhibit or kill CD133+ GBM stem cells may lead to marked improvements in patient outcome.