Oncolytic herpes simplex virus inhibits paediatric high grade glioma and diffuse intrinsic pontine glioma migration and invasion: Mechanism and potential for clinical application

INTRODUCTION: Paediatric high grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) are invasive tumours associated with poor survival, and new treatments that target brain tumour invasion are needed. Oncolytic virotherapy, which uses viruses to selectively infect and destroy cancer cells, while stimulating an anti-tumour immune response, offers a novel approach. Here, we evaluate the effect of oncolytic herpes simplex virus (HSV) 1716 on the migratory behaviour of a panel of pHGG and DIPG cell lines. METHOD: Migratory characteristics were examined using 2D (scratch assay, live cell imaging) and 3D (spheroid invasion in collagen) assays. Cell viability was examined by FACS and WST-1 assays. Levels of acetylated tubulin and glycogen synthase kinase-3 (GSK3) were evaluated by Western blot. RESULTS: HSV (multiplicity of infection 10) resulted in blockade of both migration (24h) and invasion (72h) in all cell lines. No significant cytotoxicity was demonstrated at these time points. pHGG cells demonstrated reduced velocity, loss of polarity and altered morphology in the presence of HSV 1716. HSV 1716 treatment of pHGG cells increased expression of acetylated tubulin (associated with stable rather than dynamic microtubules) and substantially reduced expression of GSK3 (a key regulator of cell migration and microtubule Dynamics). CONCLUSION: Our results demonstrate that HSV 1716 can block migration and invasion of pHGG and DIPG cells in vitro, potentially through microtubule stabilisation and inhibition of GSK3. We propose that oncolytic HSV may have therapeutic benefits for pHGG and DIPG, not only as a cytotoxic and immunogenic treatment, but as an anti-invasive agent, improving outcome for this devastating disease.