The patients` immune systems responded by producing "killer" T-cells designed to attack cancer.
The vaccine was also found to be effective in fighting “aggressively growing” tumours in mice, according to researchers, who were led by Professor Ugur Sahin from Johannes Gutenberg University in Germany.
“[Such] vaccines are fast and inexpensive to produce, and virtually any tumour antigen [a protein attacked by the immune system] can be encoded by RNA," they wrote
“Thus, the nanoparticulate RNA immunotherapy approach introduced here may be regarded as a universally applicable novel vaccine class for cancer immunotherapy.”
The paper said the three patients were given low doses of the vaccine and the aim of the trial was not to test how well the vaccine worked. While the patients` immune systems seemed to react, there was no evidence that their cancers went away as a result.
In one patient, a suspected tumour on a lymph node got smaller after they were given the vaccine. Another patient, whose tumours had been surgically removed, was cancer-free seven months after vaccination.
The third patient had eight tumours that had spread from the initial skin cancer into their lungs. These tumours remained “clinically stable” after they were given the vaccine, the paper said.
The vaccine, which used a number of different pieces of RNA, activated dendritic cells that select targets for the body`s immune system to attack. This was followed by a strong response from the "killer" T-cells that normally deal with infections.
Cancer immunotherapy is currently causing significant excitement in the medical community.
It is already being used to treat some cancers with a number of patients still in remission more than 10 years after treatment.
While traditional cancer treatment for testicular and other forms of the disease can lead to a complete cure, lung cancer, melanoma, and some brain and neck cancers have proved difficult to treat.
Being able to inject an effective treatment into a patient’s bloodstream would be a significant step forward. The vaccine also produced limited flu-like side-effects in contrast to the extreme sickness caused by chemotherapy.
Professor Alan Melcher, of the Institute of Cancer Research, said: “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.
“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.”
Dr Helen Rippon, chief executive of Worldwide Cancer Research, said “We know the immune system has great potential to be manipulated and reactivated to fight cancer cells, that’s why we’ve been funding research into this for 15 years.
“These are exciting and novel results, showing the promise of an RNA nanoparticle vaccine to do just that.”
She described the immune response in the three patients as “positive” and noted that advanced skin cancer was “a notoriously difficult cancer to treat”.
“However, more research is needed in a larger number of people with different cancer types and over longer periods of time before we could say we have discovered a ‘universal cancer vaccine’. But this research is a very positive step forwards towards this global goal,” she said.
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