Glioblastomas are high-grade brain tumors with poor prognoses, and new therapeutic approaches for these tumors are critically needed. This study revealed the underlying mechanisms of a new orphan drug, ACT001, that is currently in clinical trials for the treatment of advanced glioblastoma in Australia and China. ACT001 significantly suppressed glioma cell proliferation and induced apoptosis and cell cycle arrest in vitro, as determined by Cell Counting Kit-8 assays and flow cytometry. In addition, U-118 MG cells with high expression of p-IKKβ were sensitive to ACT001. Changes in the oxidative stress pathway in U-118 MG cells were detected with the isobaric tags for relative and absolute quantitation (iTRAQ) method. We further verified that ACT001 elevated the levels of reactive oxygen species (ROS) by regulating NF-κB-targeted MnSOD. ACT001 markedly inhibited NF-κB activation by directly binding IKKβ and inhibiting its phosphorylation. Overexpression of IKKβ markedly attenuated the changes in MnSOD and NOX1, indicating that ACT001 increased the levels of ROS by reducing the protein expression of p-IKKβ. Furthermore, ACT001 reduced cyclin B1/CDC2 expression and triggered G2/M phase arrest by increasing ROS production. ACT001 also upregulated the expression of Bax and Bim and induced apoptosis in a ROS-dependent manner. ACT001 effectively suppressed the growth of U-118 MG tumors in BALB/c nude mice and GL-261-luciferase tumors in C57BL/6 J mice. Finally, ACT001 downregulated the expression of p-p65, MnSOD, cyclin B1, CDC2, and Ki67 in U-118 MG tumor tissues. Patients with activated NF-κB signaling should thus be given priority for enrollment in future phase II clinical trials. KEY MESSAGES: ACT001 directly bind to IKKβ and inhibited its phosphorylation. The inhibition of p-IKKβ induced the generation of ROS. ACT001 promoted the generation of ROS by regulating MnSOD expression to induce G2/M phase arrest.
Keywords: Apoptosis; Glioblastoma; IKKβ; NF-κB; ROS.