1. Bcl-2/Bcl-xL inhibition predominantly synergistically enhances the anti-neoplastic activity of a low-dose CUSP9 repurposed drug regime against glioblastoma.
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Halatsch, Marc‐Eric, Kast, Richard Eric, Dwucet, Annika, Hlavac, Michal, Heiland, Tim, Westhoff, Mike‐Andrew, Debatin, Klaus‐Michael, Wirtz, Christian Rainer, Siegelin, Markus David, Karpel‐Massler, Georg, Halatsch, Marc-Eric, Westhoff, Mike-Andrew, Debatin, Klaus-Michael, and Karpel-Massler, Georg
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BCL-2 proteins , *DRUG synergism , *CELL death , *MITOCHONDRIAL membranes , *CELL proliferation , *MEMBRANE potential - Abstract
Background and Purpose: Drug repurposing represents a promising approach to safely accelerate the clinical application of therapeutics with anti-cancer activity. In this study, we examined whether inhibition of the anti-apoptotic Bcl-2 family proteins Bcl-2 and Bcl-xL enhances the biological effects of the repurposed CUSP9 regimen in an in vitro setting of glioblastoma.Experimental Approach: We applied 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays to assess cellular proliferation. Annexin V/propidium iodide and tetramethylrhodamine, ethyl ester staining were used to examine apoptosis. Western blotting, RT-PCR, and specific knockdown experiments using siRNA were employed to examine molecular mechanisms of action.Key Results: Bcl-2/Bcl-xL inhibition exerted synergistic anti-proliferative effects across established, primary cultured, and stem-like glioblastoma cells when combined with CUSP9 which had been reduced to only one tenth of its proposed original concentration (CUSP9-LD). The combination treatment also led to enhanced apoptosis with loss of mitochondrial membrane potential and activation of caspases. On the molecular level, CUSP9-LD counteracted ABT263-mediated up-regulation of Mcl-1. Silencing of Mcl-1 enhanced ABT263-mediated apoptosis which indicates that down-regulation of Mcl-1 is crucial for the induction of cell death by the combination treatment.Conclusion and Implications: These data suggest that Bcl-2/Bcl-xL inhibition enhances the susceptibility of glioblastoma cells towards CUSP9, allowing dramatic dose reduction and potentially decreased toxicity when applied clinically. A clinical trial involving the original CUSP doses (CUSP9v3) is currently ongoing in our institution (NCT02770378). The Bcl-2/Bcl-xL inhibitor ABT263 is in clinical trials and might represent a valuable adjunct to the original CUSP. [ABSTRACT FROM AUTHOR]- Published
- 2019
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