Reovirus-therapy triggers cancer self destruction
Leeds/Calgary – Oncolytic reoviruses not only kill cancer cells directly but also force them to secrete cytokines that recruit cancer killing cells from the innate and adaptive immune system. According to researchers from Leeds University (UK) and the Canadian biotech firm Oncolytics Biotech, which is conducting several Phase II study with its reovirus-based cancer treatment Reolysin, this opens up the potential of cancer treatment by "bystander" immune-mediated therapy even in the absence of live virus. Published in Molecular Cancer, researchers showed that growth media from reovirus-infected melanoma cells contained pro-inflammatory cytokins such as IL-8 and Interferon beta (INF-beta), which recruited and activated white blood cells, specifically Natural Killer (NK) cells, dendritic cells (DC) and anti melanoma cytotoxic T cells (CTL) which killed off the tumour. The effect was dependent on inactivation of the protein PKR, which protects non-cancer cells from reovirus infection, and the presence of NF-kappaB. The study shows that reovirus therapy can be effective even though reovirus is cleared shortly after infection, through immune system induction of a tumour-specific immune response that initiates apoptosis of tumour cells.