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While they have not yet determined whether the immune response is sufficient to destroy the cancer, the researchers are hopeful that the technique could one day lead to a cure for at least some types of the deadly disease.
"This would be a way to treat cancer without side effects," said senior author Ronald Levy of the Stanford University Medical Centre.
"The idea is to marshal the body's own immune system to fight cancer," Levy said, adding that he's optimistic he'll get positive results from the next clinical trial.
"We know that if you get the immune system revved up, it can attack and kill cancer."
The process has already successfully cured cancer in mice.
Study results promising
Levy's team tested the vaccine on 16 patients who were recently diagnosed with follicular B-cell lymphoma, a chronic, incurable disease.
None of the patients experienced any significant side-effects and more than 70 percent of the patients developed an immune response, the study published in the Proceedings of the National Academy of Sciences found.
This is the first time a plant-based cancer vaccine has been tested on humans. There have been a few trials of cancer vaccines developed with animal or human cells, but they have had mixed results.
Advantages
The plant-based vaccine has a number of advantages.
It can be developed much more quickly and at far less expense. It does not carry the risk of infection should the animal cells be contaminated. And the antibodies produced may also spark a stronger immune response than those developed in mammalian cells.
"Every lymphoma patient has a target on their tumour cells, but each patient's tumour has a different version of that target," Levy said.
Finding the right target requires cloning the genes from the patient's tumour.
Those genes are then injected into a virus which naturally attacks tobacco plants. This virus is scratched onto the leaves of a tobacco plant and it becomes a "protein production factor," Levy said.
A week later, the leaves are ground up and then the protein is isolated and injected into the patient.
Customised to patient
"This technology is special because it's fast and very suitable to this customised, personalised approach because each plant can be making a different person's (vaccine)," Levy told AFP.
The vaccine would not be suitable for preventative purposes, Levy cautioned.
But the same technique could one day be used to fight other diseases, Levy added.
"We use proteins for a lot of purposes in medicine like enzyme replacement and vaccines and antibodies," he said.
"Growing human cells for production of proteins is really expensive and a long process and it's hard to maintain. Growing these plants are dirt cheap... and we know how to grow tobacco plants really well." – (Sapa)
Read more:
Tobacco used to fight cancer
Cancer Centre
July 2008
