Sinularin Induces Oxidative Stress-Mediated Apoptosis and Mitochondrial Dysfunction, and Inhibits Angiogenesis in Glioblastoma Cells

Abstract

Glioblastoma multiforme (GBM) is a cancer of largely unknown cause that leads to a 5-year survival rate of approximately 7% in the United States. Current treatment strategies are not effective, indicating a strong need for the development of novel therapies. In this study, the outcomes of sinularin, a marine-derived product, were evaluated against GBM. Our cellular studies using GBM cells revealed that sinularin induces cell death. The measured half maximal inhibitory concentrations (IC50) values ranged from 30 to 6 μM at 24–72 h. Cell death was induced via the generation of ROS leading to mitochondria-mediated apoptosis. This was evidenced by annexin V/propidium iodine staining and an upregulation of cleaved forms of the pro-apoptotic proteins caspase 9, 3, and PARP, and supported by CellROXTM Green, MitoSOXTM Red, and CM-H2DCFDA staining methods. In addition, we observed a downregulation of the antioxidant enzymes SOD1/2 and thioredoxin. Upon treatment with sinularin at the ~IC50 concentration, mitochondrial respiration capacities were significantly reduced, as shown by measuring the oxygen consumption rates and enzymatic complexes of oxidative phosphorylation. Intriguingly, sinularin significantly inhibited indicators of angiogenesis such as vessel tube formation, cell migration, and cell mobility in human umbilical vein endothelial cells or the fusion cell line EA.Hy926. Lastly, in a transgenic zebrafish model, intersegmental vessel formation was also significantly inhibited by sinularin treatment. These findings indicate that sinularin exerts anti-brain cancer properties that include apoptosis induction but also antiangiogenesis.