Oncolytic herpes simplex virus: An anti-invasive therapeutic strategy for paediatric high grade glioma and diffuse intrinsic pontine glioma

Paediatric high grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) are invasive tumours associated with poor survival. Oncolytic virotherapy, which uses viruses to selectively infect and destroy cancer cells and/or stimulate an anti-tumour immune response, offers a novel treatment approach. Here, we evaluate the effects of oncolytic herpes simplex virus (HSV) 1716 on migration and invasion in in vitro and in vivo models of pHGG and DIPG. In vitro migratory characteristics were examined using 2D (scratch assay, live cell imaging) and 3D (spheroid invasion in collagen) assays. Oncolytic HSV resulted in blockade of both migration and invasion in all pHGG and DIPG cell lines and this did not appear to be a consequence of cytotoxicity or altered proliferation. pHGG cells demonstrated reduced velocity, loss of polarity and changed morphology in the presence of virus. Oncolytic HSV altered pHGG cytoskeletal dynamics, stabilising microtubules through accumulation of post-translational tubulin modifications. Furthermore, oncolytic HSV treatment of pHGG cell lines inhibited glycogen synthase kinase-3 (a key regulator of cell migration and microtubule dynamics) and prevented localised clustering of adenomatous polyposis coli to the leading edge of cells. Importantly, oncolytic HSV treatment reduced tumour infiltration and enhanced therapy in a mouse orthotopic xenograft model of DIPG. In conclusion, this study is the first to demonstrate that it is possible to target migration and invasion of pHGG and DIPG using oncolytic HSV. We propose that oncolytic HSV may have therapeutic benefits for pHGG and DIPG as an anti-invasive agent, improving outcomes for these devastating diseases.