High energy levels cause glioblastoma cells to proliferate; low levels cause them to grow less and to migrate. This study discovered that a molecule called miR-451 coordinates this grow-or-go behavior, which is closely linked to the cells' ability to invade and spread. Thus, the molecule might be a biomarker for predicting survival in patients with glioblastoma multiforme and may serve as a target to develop drugs to fight these tumors.