The missing effect of ABCG2 methylation on GBM patients’ survival could be explained by the fact that temozolomide, which is the most applied cytostatic for patients with GBM, is not a substrate of ABCG2[43], and thus modulation of ABCG2 expression should not affect the therapy and survival of GBM patients. The gene discussed is ABCG2; the disease is glioblastoma.