Sanaz Dastghaib - Endocrine and Metabolism Research Center, Nemazee Hospital, Shiraz University of Medical Sciences, Shiraz, Iran
Shahla Shojaei - Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB R۳E ۰J۹, Canada
Pooneh Mokaram - Department of Biochemistry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran /Autophagy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
Saeid Ghavami - Department of Human Anatomy and Cell Science, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, MB R۳E ۰J۹, Canada/ Autophagy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran

Introduction; Chemo-resistance is a crucial barrier to effective treatment for glioblastoma (GB), the most common malignant primary brain tumor. Temozolomide (TMZ) is the first-line chemotherapeutic drug in GB; nevertheless, chemo-resistance has significantly reduced TMZ effectiveness over time. In the last decade, the combination of simvastatin (Simva), an anti-hyperlipidemic medication, alongside chemotherapy agents, have attracted more attention to improving therapeutic efficacy. Studies have demonstrated that unfolded protein response (UPR) activation followed by endoplasmic reticulum (ER) stress may impart resistance to chemo-agents and contribute to treatment failure. In the current investigation, we addressed the involvement of UPR in Simva-TMZ-induced cell death. Methods: MTT assay was used for TMZ, Simva and mevalonate to find the drugs' proper dose and duration time. U۲۵۱ GB cell was pretreated with Simva (۱ μM) for ۴ h and then co-treated with TMZ (۱۰۰ μM) for ۷۲ h. To assess the status of cell death, flow cytometry PI assay was performed. To detect markers of UPR, western blot analysis was used with different anti-bodies (GRP۷۸, IRE-۱, XBP-۱s, ATF۶, eIF۲α, P-eIF۲α, P-H۲A, Cleaved-Caspase-۳, and GAPDH as loading control). Results: Interestingly, Simva-TMZ significantly decreased cell viability and increased apoptotic cell death independent of the mevalonate cascade. Moreover, Simva–TMZ induced UPR elements, manifesting an increase in GRP۷۸, XBP-۱ splicing, p-eIF۲α, ATF۶, and caspase-۳. Conclusion: Taken together, these results uncovered a novel role of the UPR pathway in Simva that enhances TMZ-induced cell death in U۲۵۱ cells. These results highlight a possible strategy of targeting the UPR to overcome the glioblastoma chemo-resistance.

Glioblastoma, Simvastatin, unfolded protein response, IRE-۱, cell death