Adaptive Immune Response to and Survival Effect of Temozolomide- and Valproic Acid-induced Autophagy in Glioblastoma

Background/Aim: The combination of radiotherapy, temozolomide and valproic acid (VPA) has shown some promise in retrospective analyses of patients with glioblastoma, although their mechanisms of action remain unknown. Materials and Methods: We investigated the in vitro and in vivo effects of pretreating glioma cells with temozolomide and VPA as an immunization strategy to boost an adaptive immune response in a syngeneic mouse model. Results: Temozolomide and VPA induced autophagy in GL261 glioma cells, and caused tumor antigen-specific T-cells to become activated effector T-cells. Mice with a pre-existing glioma showed no improvement in clinical outcome when immunized with temozolomide-and VPA-treated glioma cells. Conclusion: Although temozolomide and VPA treatment of glioma cells can boost the adaptive immune response, in the context of a vaccine therapy, additional factors are necessary to eradicate the tumor and improve survival.