Cycling hypoxia also induced ROS-mediated activation of hypoxia-inducible factor 1alpha (HIF-1α) and NF-κB, which was associated with increased expression of the antiapoptotic protein BCL-XL in GBM cell lines and xenograft tumors, resulting in temozolomide resistance in GBM [113]. Here, BCL2L1 is linked to glioblastoma.