New Smallpox-Radiotherapy Combination May Improve Prostate Cancer Treatment

March 24, 2016 – Researchers found that using a genetically modified strain of the vaccinia virus ( the active component of the smallpox vaccine) to infect and multiply inside cancer cells combined with radioiodide therapy was significantly more effective at killing cancer cells and slowing tumor growth than the single treatments alone.

Although at an early stage, the study, published in the journal Gene Therapy,1 paves the way for future clinical studies of viral and radiotherapy combinations – with the potential of improving the treatment of prostate cancer.

Scientists at The Institute of Cancer Research, London, in collaboration with other research teams in the UK, US and Australia, used human prostate cancer cell lines and studies in mice to investigate the cancer–killing properties of the modified virus on its own and in combination with different types of radiotherapy.

The protein – called the sodium-iodide symporter – allows iodide ions to travel into cells. Using this property, the researchers exposed the prostate cancer cells infected with the virus to a radioactive form of iodine, meaning that radioactive iodine ions were able to enter the cells and kill them.

Radioiodide therapy is already commonly used in the treatment of thyroid cancers – as most of the radioactive iodide is taken up by the thyroid cells that naturally have the channel protein on their surface. This study shows the potential of radioiodide therapy to treat other cancers such as prostate cancer.

The researchers also investigated the modified vaccinia virus in combination with external beam radiotherapy and found that this also increased the rate of prostate cancer cell death. Mice that were treated with viral therapy and radiotherapy survived four times as long as those that were treated with virus alone.

Figure 1. Prostate gland.2 

“Using viruses to kill cancer cells is an innovative way of treating cancers and an exciting area of research. Our study demonstrates the potential of the vaccinia virus to target cancer cells, and shows how its cancer-killing effects can be enhanced by combining the treatment with radiotherapy,” said Professor Kevin Harrington, Professor of Biological Cancer Therapies at the ICR. 


1. Mansfield DC, Kyula JN, Rosenfelder N, et al. Oncolytic vaccinia virus as a vector for therapeutic sodium iodide symporter gene therapy in prostate cancer. Gene Therapy advance online publication 18 February 2016; doi: 10.1038/gt.2016.5.

2. New viral-radiotherapy combination could treat prostate cancers.