NDRG2 and glioblastoma: Promoter hypermethylation of the NDRG2 gene increased the OR for GBM development by 1.45 (1.25–1.85, p < 0.001), while promoter hypermethylation of the GLI1 gene increased the OR by 1.26 (1.14–1.45, p < 0.001).