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Surfing 'Trojan-horses' stop tumour regrowth after chemotherapy or radiotherapy
By The University of Sheffield

World-leading experts have discovered white blood cells called macrophages surge into tumours from the blood after frontline therapies like chemotherapy or radiotherapy, and are now exploiting this to deliver a second potent blow to stop tumours growing back.

Each macrophage then releases large amounts of virus inside the tumour.

The virus then kills the cancer residue from within preventing regrowth or further spread of the cancer to other parts of the body.

"Our 'Trojan-horse' can convert a patient's own white blood cells into tiny tumour-killing machines which fight to prevent tumour regrowth after the end of chemo or radio therapy treatment," said Professor Lewis.

Dr Muthana added: "With the initial support of the Yorkshire Cancer Research (YCR) and latterly Prostate Cancer UK, our new therapy has been developed to treat prostate cancer; however, it has the potential to be used to treat patients with any form of cancer."

Dr Kate Holmes, Head of Research at Prostate Cancer UK said: “This research is an exciting development on the ‘Trojan Horse’ technique. It demonstrates that this innovative method of delivering a tumour-killing virus direct to the cancer site is successful at reducing the development of advanced prostate tumours in mice which have been treated with chemotherapy and radiotherapy.

BBC News reports that an experimental therapy hides “cancer killing viruses inside the immune system in order to sneak them into a tumour” and that this “Trojan-horse therapy ‘completely eliminates’ cancer in mice”.

This news is based on early stage research into a new type of cancer treatment, using viruses to target and attack cancerous tumours. The current study took advantage of large immune system cells called macrophages that increase in number in the tumour after standard chemotherapy and radiation treatment.

The scientists treated mice that had prostate cancer with chemotherapy, and then used these immune system cells to deliver a virus to the remaining tumour. This virus then multiplied and attacked the tumour cells. This research provides early evidence that using the immune system’s existing cells may offer a mechanism by which to deliver novel cancer treatments. This research is still in its early stages, and trials in people will be needed to ensure that the approach is safe and effective for treating human prostate cancer.

The study was carried out by researchers from the University of Sheffield Medical School and Uppsala University, and was funded by the Prostate Cancer Charity and Yorkshire Cancer Research. The study was published in the peer-reviewed journal Cancer Research.

The research was covered well by the BBC. The researchers used a type of immune cell called a macrophage to hide the virus and deliver it to the tumour. Macrophages are drawn to tumour sites after chemotherapy and radiation treatment, and the researchers were interested in exploiting this natural process to deliver further cancer therapies. Animal studies are often used in the early stages of new treatment research. What did the research involve?

In the first, two groups of mice were treated with chemotherapy. Two days after the treatment ended, the researchers injected one group of mice with the macrophages housing the tumour-attacking virus and provided no further treatment to the other group (which acted as a chemotherapy-alone control group).

The researchers used a similar approach with radiation therapy, with all mice receiving radiation treatment and, two days after the end of treatment, injecting one group with the macrophage-virus combination, and discontinuing treatment in the radiation-only control group.

The researchers then monitored tumour regrowth, spread and mouse survival for 42 days, and compared these outcomes between the two groups of mice.

The researchers found that, compared to chemotherapy alone, mice treated with the macrophage delivered virus prevented tumour regrowth for 35 days. The tumours in these mice also did not spread (metastasise) to the lungs, although some of the virus was detected in the lung tissue.

The researchers say that further research is needed to see if this combined treatment “approach will be equally effective in prostate cancer patients”. For now this is an interesting approach to treating prostate tumours, but we will have to wait and see whether the promise of this early stage animal study bears promise for the treatment of advanced prostate cancer in people.