German scientists have reported making progress towards a vaccine against cancer.
While vaccines are mostly known for their preventative role, the latest study, outlined in the journal Nature, describes a vaccine strategy against existing tumours that harness the body's immune mechanisms normally used to combat viral infection.
The technique, described as "promising", is in early clinical trials and has so far been tested only in mice and three patients with advanced melanoma.
However, scientists say it raises the possibility of a universal vaccine for cancer immunotherapy.
The findings prompt the question: 'why have our bodies not evolved to spot the spread of cancer and launch a defence against it?'
One important reasons is that cancer cells are similar to normal cells and the immune system avoids attacking them.
Another reason is that as cancer spreads, it manages to dodge giving off strong inflammatory signals that would rouse an immune response.
Likened to creating a 'Trojan horse', under laboratory conditions scientists have created nanoparticles containing cancer RNA to persuade the body that a viral pathogen has launched an invasion.
In mice experiments, they targeted immune system cells called dendritic cells by using an intravenously administered vaccine made up of RNA nanoparticles.
They found that adjusting the net electrical charge of the nanoparticles to be slightly negative was enough to efficiently target these dendritic cells.
Hopes for a Universal Cancer Vaccine
They say that if future studies prove this treatment works, it could form the basis for a universal form of cancer therapy.
In an editorial in the same journal, Jolande de Vries and Carl Figdor from Radboud University Medical in the Netherlands comment that the findings may "give a strong boost to the vaccine field, and the results of forthcoming clinical studies will be of great interest."
An 'Exciting Study'
Commenting on the findings to the Science Media Centre, Alan Melcher, professor of translational immunotherapy at the The Institute of Cancer Research, says: "Immunotherapy for cancer is a rapidly evolving and exciting field. This new study, in mice and a small number of patients, shows that an immune response against the antigens within a cancer can be triggered by a new type of cancer vaccine.
"This vaccine is given into the blood, and comprises very small nanoparticules made up of fat joined to RNA (a type of genetic code for the tumour antigens). These nanoparticles target particular cells in the mice, called dendritic cells, which are key to stimulating an immune response.
"Although the research is very interesting, it is still some way away from being of proven benefit to patients. In particular, there is uncertainty around whether the therapeutic benefit seen in the mice by targeting a small number of antigens will also apply to humans, and the practical challenge of manufacturing nanoparticles for widespread clinical application."
'Systemic RNA delivery to dendritic cells exploits antiviral defence for cancer immunotherapy', L Kranz et al, Nature.
'Cancer vaccine triggers antiviral-type defences', J Vries, C Figdor, Nature.
Science Media Centre.