Gene therapy with apoptosis-associated speck-like protein, a newly described schwannoma tumor suppressor, inhibits schwannoma growth in vivo

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2019-07, Vol.21 (7), p.854-866
• Main Authors: Ahmed, Sherif G, Abdelnabi, Ahmed, Maguire, Casey A, Doha, Mohamed, Sagers, Jessica E, Lewis, Rebecca M, Muzikansky, Alona, Giovannini, Marco, Stemmer-Rachamimov, Anat, Stankovic, Konstantina M, Fulci, Giulia, Brenner, Gary J
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Basic and Translational Investigations; Biomarkers, Tumor - genetics; Cancer Pain - etiology; Cancer Pain - prevention & control; CARD Signaling Adaptor Proteins - administration & dosage; CARD Signaling Adaptor Proteins - genetics; Cell Proliferation; Dependovirus - genetics; DNA Methylation; Genetic Therapy; Humans; Male; Mice; Neurilemmoma - genetics; Neurilemmoma - pathology; Neurilemmoma - therapy; Prognosis; Promoter Regions, Genetic; Tumor Cells, Cultured; Xenograft Model Antitumor Assays
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noz065

Abstract Background We evaluated apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) as a schwannoma tumor suppressor and explored its utilization in a schwannoma gene therapy strategy that may be translated to clinical use. Methods ASC protein expression and mRNA level were assessed in human schwannoma by immunohistochemistry and quantitative PCR, respectively. Methylation- specific PCR was used to assess ASC promoter methylation. The effect of ASC overexpression in schwannoma cells was evaluated through ATP-based viability, lactate dehydrogenase release, and apoptosis staining. Western blotting and colorimetric assay were used to test the effect of ASC overexpression on endogenous pro-apoptotic pathways. Bioluminescence imaging, behavioral testing, and immunohistochemistry in human xenograft and murine allograft schwannoma models were used to examine the efficacy and toxicity of intratumoral injection of adeno-associated virus (AAV) vector encoding ASC. Results ASC expression was suppressed via promoter methylation in over 80% of the human schwannomas tested. ASC overexpression in schwannoma cells results in cell death and is associated with activation of endogenous caspase-9, caspase-3, and upregulation of BH3 interacting-domain death agonist. In a human xenograft schwannoma model, AAV1-mediated ASC delivery reduced tumor growth and resolved tumor-associated pain without detectable toxicity, and tumor control was associated with reduced Ki67 mitotic index and increased tumor-cell apoptosis. Efficacy of this schwannoma gene therapy strategy was confirmed in a murine schwannoma model. Conclusion We have identified ASC as a putative schwannoma tumor suppressor with high potential clinical utility for schwannoma gene therapy and generated a vector that treats schwannomas via a novel mechanism that does not overlap with current treatments.