Chapter 7 Intratumoral heterogeneity associated with glioblastoma drug response and resistance

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. Despite aggressive multimodal treatment, relapse is inevitable with patients succumbing to disease 15months after diagnosis. Poor prognosis may be attributed to significant intratumoral heterogeneity at the genomic, cellular, and functional levels of a single tumor. However, this heterogeneity highlights the need to understand mechanisms of therapeutic resistance to give insight into the underpinnings of treatment failure. Thus, we review some of the various tumor-intrinsic molecular mechanisms, as well as tumor-extrinsic factors that support GBM progression and therapeutic resistance.