Scientists have shown how a promising viral therapy that delivers a double blow to cancer can sneak up on tumors undetected by hitching a ride on blood cells.
The work, led by researchers from the University of Leeds and The Institute of Cancer Research (ICR), reveals how the 'hitch-hiking' virus is shielded from antibodies in the blood stream that might otherwise neutralize its anti-cancer properties.
The findings, from a study in patients, suggest that viral therapies like this can be effectively injected into the bloodstream during routine outpatient appointments - just like standard chemotherapy agents - making them potentially suitable for use against a wide range of cancers.
Reovirus is a promising new way of treating cancer that attacks the disease on two fronts. Not only does the virus kill cancer cells directly, but it also triggers an immune response - like a vaccine - that helps eliminate residual cancer cells.
Many patient trials of reovirus are currently underway, including several in the UK led by the same University of Leeds and ICR scientists. Up until now, however, doctors have not been sure about the best way to deliver the experimental treatment. Although the virus can be injected directly into tumors, this is a relatively complicated procedure requiring considerable technical expertise. This delivery method also makes it difficult to treat tumors deep within the body, such as the liver, lungs, pancreas, and stomach.
Researchers had been concerned that reovirus might not reach the tumors it was supposed to treat if it was delivered intravenously, like standard chemotherapy agents are. They had expected that antibodies in the blood would mop up and neutralize the virus before it arrived at its intended target.
But now tests on a small group of patients have shown that this is not the case. In fact, not only did the virus stay active during its journey through the bloodstream but it also homed in on cancer cells, ignoring nearby healthy tissue.
University of Leeds' researcher Professor Alan Melcher, who receives funding from Cancer Research UK, jointly led the study. He said: "It seems that reovirus is even cleverer than we had thought. By piggybacking on blood cells, the virus is managing to hide from the body's natural immune response and reach its target intact. This could be hugely significant for the uptake of viral therapies like this in clinical practice."