OLIG2 and glioblastoma: To further examine the clinical significance of the classification system in GBM samples, we performed IHC staining of sixteen gene makers selected from Ac-G/Class-G/Neo-G/Opc-G/Undiff-G clusters in 137 GBM samples (Ac-G: ALDOA, MGST1, and ANXA1; Class-G: MRC2, RAB34, SPRY1, and SEMA6D; Neo-G: TUBB2A, TERF2IP, and NFIB; Opc-G: PTPRZ1, MARCKSL1, and OLIG2; and Undiff-G: FABP5, TIMP1, and CRYAB) (Figure 6(a)).