Evaluating the Role of Nrf-2/HO-1 Pathway in Glioblastoma Treatment Efficacy: A Co-Culture Study

Abstract

Objective: Glioblastoma (GB) is a highly lethal form of brain tumor. Although standard therapy appears to be effective, the survival time is quite short, and the recurrence rate is high. Bortezomib (BTZ), is a proteasome inhibitor, used in GB therapies and resulted in serious off-target effects. Carfilzomib (CFZ), is an alternative for BTZ, has known with nonserious off-target effects. This study aimed to examine the potential off-target effects caused by BTZ and CFZ in terms of the therapy related activation of antioxidant mechanisms regarding to Nuclear factor (erythroid-derived 2)-like 2 (Nrf-2)/Heme Oxygenase-1 (HO-1)-dependent response. Methods: GB cells were co-cultured with heathy astrocyte (HA) cells to mimic the tumor microenvironment in some extent. Cell viability was determined following ionizing radiation (IR), temozolomide (TMZ), BTZ and CFZ alone and in combination. Nrf-2 and HO-1 protein expressions were analyzed by western blotting assay. Results: Co-culture results showed that the GB cells in the BTZ-treated groups expressed higher levels of Nrf-2 and HO-1 than in the CFZtreated groups. In the HAs, the group treated with CFZ showed higher Nrf-2 expression than the group treated with BTZ alone, while the same groups in combination with TMZ&IR showed exactly opposite results. HO-1 expression was also not seen in any of the HA groups. Conclusion: The significant increase in Nrf-2 levels in the CFZ-treated group in the HAs could also be interpreted as CFZ promoting the defence of healthy cells against therapy-induced stress conditions. Although further studies are needed, these preliminary results show that the evaluation of CFZ as a second-line therapy could be a milestone for the treatment of GB.