Tobacco plant vaccine a cure for cancer?

Jul 22 2008

Scientists in the U.S. say the tobacco plant could be used to "grow" key components of a cancer vaccine; they suggest that the same plant which is responsible for causing cancer may offer a way to treat the disease.

The scientists have developed a plant-based cancer vaccine which is capable of marshalling the body's immune response and they say it can be tailored to suit a patient's specific tumour type.

The scientists from Stanford University in California say the tobacco plant could be used to tackle a form of lymphoma.

The plants are used as factories for an antibody chemical specific to the cells which cause follicular B-cell lymphoma, a type of non-Hodgkin's lymphoma.

The antibodies are placed into a patient newly-diagnosed with the disease, in order to "prime" the body's immune system to attack any cell carrying them.

If the process is successful, the body would then recognise and destroy the lymphoma cells, but as every patient's antibodies are different they need to be produced quickly once the diagnosis is made.

While the concept is not novel, attempts previously made to grow such antibodies inside animal cells, have produced mixed results.

In theory a plant-grown vaccine could be much cheaper and would carry less risk to the patient, as animal cells might hold unknown viruses.

Lead researcher Dr. Ronald Levy says the technology is appealing and relatively straightforward.

Once a patient's cancer cells are isolated in the laboratory, the gene responsible for producing the antibody is extracted and added to the "tobacco mosaic virus" - then the plants are "infected" with the virus, and as it spreads through the cells, the added gene starts the process of producing large quantities of the antibody.

Finding the right target requires cloning the genes from the patient's tumour which 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," a few leaves are taken, ground up, and the antibody extracted from them - only a few plants are needed to make enough vaccine for a patient.

Experts say the speed of the production process means patients could wait for their own tailored vaccine rather than undergoing other treatment and it could be a way to treat cancer without side effects.

The experimental vaccine has already successfully cured cancer in mice and has been tested 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.

This is the first time a plant-based cancer vaccine has been tested on humans and it has a number of advantages in that it can be developed much more quickly and at far less expense.

Levy says the technology is special because it is fast and suited to a customized, personalized approach because each plant can be making a different person's vaccine, but it would not be suitable for preventative purposes.

While they have yet to determine whether the immune response is sufficient to destroy the cancer, the researchers hope the technique will one day lead to a cure for at least some forms of cancer and Dr.Levy says the same technique could one day be used to fight other diseases.

The study is published in the Proceedings of the National Academy of Sciences.