CDKN2A and glioblastoma: CDKN2A/B loss was found in six of thirteen glioblastomas of RTK I subtype (46%) (Figure 2D), in ten of 15 glioblastomas of RTK II subtype (67%) (Figure 2E), and in four of 17 glioblastomas of MES subtype (24%) (Figure 2F).