MYC and glioblastoma: Immunohistochemical staining of the GSC-derived intracranial xenografts with or without As2O3 treatment showed a marked reduction of c-Myc protein levels in the majority of tumor cells after As2O3 treatment, indicating c-Myc as a downstream effector of As2O3 treatment in GBM tumors (Figure 6F and 6G, Supplementary Figure S4E and S4F).