Troxerutin Potentiated Temozolomide Induced Antitumor Effect in 2D and 3D Glioblastoma Models

Glioblastoma (GBM) is a highly aggressive brain tumour characterised by rapid proliferation and high invasiveness. Temozolomide (TMZ) is the first-line chemotherapy, but its efficacy is often compromised by intrinsic or acquired resistance and significant side effects. Recent studies have demonstrated that combining TMZ with natural compounds can enhance therapeutic efficacy through synergistic mechanisms and reduce systemic toxicity. In this study, the adjuvant potential of troxerutin (TROX), a natural flavonoid present found in tea, coffee, cereals, fruits and vegetables, and known for its antioxidant and anti-inflammatory properties, was evaluated in an in vitro model of human U87 cells. The TROX–TMZ combination showed a significant synergistic effect, effectively reducing cell viability, clonogenic capacity, migration and epithelial-mesenchymal transition (EMT), as well as promoting apoptosis. The combined treatment also modulated oxidative stress and inflammation by activating the KEAP1/NRF2 axis, resulting in increased levels of HO-1, GSH and SOD1, and decreased ROMO1, ROS, nitrites and pro-inflammatory cytokines (IL-6, TNF-α and IL-1β). These effects were also confirmed in three-dimensional models (spheroids), suggesting that the combination exerts significant antitumor activity. These results indicate that TROX could represent an effective adjuvant in the treatment of GBM, providing a novel therapeutic strategy to potentiate the antitumor effects of TMZ.