Abstract BACKGROUND Diffuse Midline Gliomas (DMGs) present formidable challenges in neuro-oncology, prompting the exploration of innovative therapeutic strategies. Repurposing approved drugs, particularly those exhibiting multifaceted effects, holds promise for addressing these challenges efficiently. In this study, we investigate the potential of trifluoperazine (TFP), an antipsychotic medication, with a specific focus on its mitochondrial-targeted actions in DMGs. METHODS TFP, a phenothiazine derivative, displayed robust in vitro anticancer activity against DMGs. Our investigation explored the molecular mechanisms underlying TFP’s interaction with mitochondria, emphasizing its influence on mitochondrial function, membrane potential, and reactive oxygen species (ROS) production. TFP is well known to induce irreversible Ca2+ release from intracellular stores by directly interacting with calmodulin 2 (CaM2) at the inositol triphosphate receptor (IP3R), leading to IP3R opening. In DMGs, intracellular Ca2+ plays a pivotal role in gene expression, cell motility, differentiation, and survival. TFP disrupts calcium homeostasis by elevating intracellular Ca2+ concentration, thereby inhibiting DMG invasion and growth. DMG cell lines, exhibiting heightened CaM2 expression compared to control healthy astrocyte cells, display increased sensitivity to TFP. RESULTS Remarkably, mitochondrial homeostasis was seriously affected by TFP, and a loss of mitochondrial membrane potential, ROS overproduction and fragmentation of mitochondrial network was observed. This mitochondrial stress, coupled with ER stress, activated the integrated stress response. We demonstrated that TFP induces cell death triggered by a poor ATP content, observed in TFP-treated cells as a consequence of a dramatic decrease in OXPHOS metabolism due to mitochondrial stress. CONCLUSIONS Our findings underscore TFP’s potential as a targeted therapeutic agent against DMGs, offering a better understanding of its impact on mitochondrial and intracellular signaling pathways. As the mitochondrial landscape remains critical in DMG biology, the observed mitochondrial damage-induced oxidative stress provides valuable insights for future investigations into the clinical application of TFP in neuro-oncology.
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