Reovirus may be able to eliminate cancer cells from autologous stem cell transplants

Medical studies show that a common virus may be able to eliminate cancer cells from autologous stem cell transplants.

Researchers at Calgary-based Oncolytics Biotech Inc., have patented a way to use the reovirus to purge cancer cells from autologous stem cell transplants that are reintroduced to the body following high-dose chemotherapy. Autologous transplantation following high-dose chemotherapy is a proven treatment alternative for many types of cancer and is extensively used by doctors for both solid tumours and tumours of the blood. In fact, autologous blood and bone marrow transplant procedures surpass the number of transplants derived from donors.

During the procedure, blood stem cells are extracted from a patient prior to high-dose chemotherapy. Once the chemotherapy is completed, the patient's own blood stem cells are transplanted back into the patient. The primary advantage of autologous transplants is that there is no risk of rejection.

However, it has been estimated that as many as 30 per cent of these autologous stem cell transplants are contaminated by cancer cells, and there is a risk that they may contribute to clinical relapse of the cancer by reintroducing cancer cells back into the body.

"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," says Dr. Matt Coffey, Chief Scientific Officer for Oncolytics.

When introduced to the blood, the reovirus enters cancer cells, replicates within them and ultimately kills them. It 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. The results of a study to purge cancer cells from autologous stem cell preparations using the reovirus were previously published in the March 13, 2003 issue of Blood. Researchers concluded that the use of reovirus may be an effective way to purge cancer cells in blood used for ex-vivo autologous stem cell transplants.

The link to reovirus' cancer-killing ability was established after it was discovered that it reproduces well in various cancer cell lines including those found in blood cancers. "Having an effective method to purge cancer cells from autologous blood stem cell transplants may offer doctors another important tool in fighting cancer," said Dr. Coffey. "Patenting this innovation provides us with an important extension of the potential use of the reovirus for the treatment of cancer."