We also studied the protein amount of GRP78, IRE1, XBP1s, ATF6, eIF2α, and phospho-eIF2α (p-eIF2α) proteins, which are key markers of the UPR pathway in the GBM cell models upon treatment with TMZ, Simva, and Simva-TMZ, after 72 h. Here, ATF6 is linked to glioblastoma.