The virus attacks both tumours and healthy cells, known as fibroblasts, that have been 'tricked' into protecting the cancer from the immune system.
Any existing treatment that kills 'tricked' fibroblasts, may also destroy those in the bone marrow and skin.
Researchers said it is the first time cancer-associated fibroblasts within solid tumours have been specifically targeted in this way.
Dr Kerry Fisher, from the University of Oxford's department of oncology, who led the research, said: 'Even when most of the cancer cells in a carcinoma are killed, fibroblasts can protect the residual cancer cells and help them to recover and flourish.
'Until now, there has not been any way to kill both cancer cells and the fibroblasts protecting them at the same time, without harming the rest of the body.
'Our new technique to simultaneously target the fibroblasts while killing cancer cells with the virus could be an important step towards reducing immune system suppression within carcinomas and should kick-start the normal immune process.'
The virus, called enadenotucirev, is already used in clinical trials for treating cancers that start in the pancreas, colon, lungs, breasts, ovaries or prostate.
The scientists attached a protein, called a bi-specific T-cell engager, to the virus.
One end of the protein was targeted to bind to fibroblasts, while the other end specifically stuck to T-cells - a type of immune cell that is responsible for killing defective cells.
Binding the two together triggered the T-cells to kill fibroblasts that are attached to tumours.
Dr Nathan Richardson, head of molecular and cellular medicine at the Medical Research Council (MRC), which was involved in funding the study, said: 'Immunotherapy is emerging as an exciting new approach to treating cancers.
'This innovative viral delivery system, which targets both the cancer and surrounding protective tissue, could improve outcomes for patients whose cancers are resistant to current treatments.
The team, whose findings were published in the journal Cancer Research, tested the therapy on mice and fresh human cancer samples collected from patients.
They also tested the virus on samples of healthy human bone marrow and found it did not cause toxicity.
If further safety testing is successful, it could be tested in cancer patients next year.
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