Virus Purges Cancer Cells in Stem Cell Transplants

A common enteric virus may be able to eliminate cancer cells from autologous stem cell transplants following chemotherapy.

A new proprietary formulation of the human respiratory enteric orphan virus (reovirus) called Reolysin is designed to purge cancer cells from autologous stem cell transplants that are reintroduced to the body following high-dose chemotherapy. When introduced into the blood, the reovirus enters cancer cells, replicates within them, and ultimately kills them. The reovirus works by replicating within cancer cells that have an activated Ras pathway, a common mutation that is shared by approximately two-thirds of all human cancers. Reolysin was developed by Oncolytics Biotech (Calgary, Canada).

Tumors bearing an activated Ras pathway are deficient in their ability to activate the anti-viral response mediated by RNA-activated PKR, the protein-kinase host cellular protein. Since PKR is responsible for preventing reovirus replication, tumor cells lacking the activity of PKR become susceptible. In tumor cells with an activated Ras pathway, the reovirus is able to freely replicate and eventually kill the host tumor cells. As cell death occurs, progeny virus particles are then free to infect surrounding cancer cells. This cycle of infection, replication, and cell death is believed to be repeated until there are no longer any tumor cells carrying an activated Ras pathway.

If we can use our reovirus-based therapy, Reolysin, to purge the blood products of cancer cells before they are reintroduced to the body, it could represent an important step forward in increasing the success of these transplants, said Dr. Matt Coffey, chief scientific officer for Oncolytics. Oncolytics has concluded patient follow-up in its Canadian phase I clinical trial examining the use of Reolysin in recurrent malignant glioma, one of the deadliest forms of brain cancer.

Reovirus, an acronym for respiratory enteric orphan virus, is generally believed to inhabit the respiratory and bowel systems in humans. The disease is non-pathogenic, meaning there are typically no symptoms from infections.