OLIG2 and glioblastoma: In the genomic analysis of glioblastoma subtypes, Verhaak et al. 21 found that the majority of secondary glioblastomas have proneural profiles expressing oligodendrocytic development genes such as PDFGRA and OLIG2. Notably, the proneural subtype is less responsive to concurrent chemotherapy and radiation than the classical, mesenchymal, and neural subtypes 21.