Graphene Oxide Modulates ROS Production and Apoptotic Responses to Bortezomib in Human Glioblastoma Cells: An In Vitro Study

Glioblastoma multiforme (GBM) remains one of the most aggressive and treatment-resistant brain tumors, characterized by rapid proliferation and poor patient prognosis. Novel therapeutic strategies are urgently needed to improve clinical outcomes. In this study, we investigated the cytotoxic and pro-apoptotic effects of bortezomib (BORT), a proteasome inhibitor, and graphene oxide (GO), a nanomaterial with known anticancer potential, on human glioblastoma cell lines. Treatment with BORT and GO, both individually and in combination, significantly reduced cell viability in a dose-dependent manner, as determined by MTT. In this study, we observed enhanced apoptotic cell death, accompanied by increased activation of both caspase-8 and caspase-9, indicating simultaneous engagement of extrinsic and intrinsic apoptotic pathways. Western blot analysis demonstrated downregulation of anti-apoptotic proteins Bcl-2 and upregulation of pro-apoptotic markers (NOXA, cleaved PARP). A central finding of this work is the pronounced increase in intracellular reactive oxygen species (ROS) levels following BORT–GO treatment. The elevated ROS levels observed in BORT–GO-treated cells compared with free bortezomib therefore suggest that GO-mediated oxidative stress may amplify proteasome inhibition-induced apoptosis, which is particularly visible in the A172 and LN229 cell lines. Notably, the combination of BORT and GO may suggest a potential cooperative mechanism through proteasome inhibition and oxidative stress induction. These findings indicate that graphene oxide may modulate the antitumor efficacy of bortezomib in a cell line-dependent manner and support further investigation of this combination as a promising therapeutic approach for glioblastoma.