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Neuro Oncol. 2019 Apr 12. pii: noz065. doi: 10.1093/neuonc/noz065. [Epub ahead of print]

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

Author information

1
Department of Anesthesiology, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States.
2
Department of Neurology, Massachusetts General Hospital, and NeuroDiscovery Center, Harvard Medical School, Boston, MA, United States.
3
Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear and Department of Otolaryngology, Harvard Medical School, Boston, Massachusetts, USA.
4
Harvard Program in Speech and Hearing Bioscience and Technology, Boston, Massachusetts, USA.
5
Biostatistics Center, Massachusetts General Hospital, Boston, MA, United States.
6
Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA and Jonsson Comprehensive Cancer Center (JCCC), University of California, Los Angeles.
7
Molecular Pathology Division, Massachusetts General, Boston, MA.
8
Cancer Center, Massachusetts General Hospital, Boston, MA, United States.

Abstract

BACKGROUND:

We evaluated Apoptosis-associated speck-like protein (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 asses 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.

KEYWORDS:

AAV1; ASC; gene therapy; methylation; schwannoma

PMID:
30977509
PMCID:
PMC6620641
[Available on 2020-07-11]
DOI:
10.1093/neuonc/noz065

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