Plant Pharming: Old Crops Learn New Tricks

Meredith Hanel
11 February 2013

Above: Tobacco field (@istockphoto.com/DrBouz)

Did you know? One pharmed product produced using tobacco binds to tooth decay bacteria and prevents it from sticking to teeth. It has been approved in Europe.You probably don't normally associate tobacco with good health, or carrots with cutting-edge medical breakthroughs. But all that might be about to change, thanks to “pharming,” a technique that uses genetically engineered plants or animals to make pharmacologically important proteins. These proteins include vaccines to protect against diseases like non-Hodgkin’s lymphoma and therapeutic proteins to treat conditions like Gaucher disease.

Pharming works by inserting a segment of DNA that codes for a particular protein into the genome of a host plant or animal. In the case of vaccine production, it will be a protein that causes the immune system to respond to a particular threat. For example, non-Hodgkin’s lymphoma is a cancer of the white blood cells. Patients need a vaccine that directs their own immune system to kill the tumours. But since each patient's tumours are unique, it takes considerable amounts of time (and money) to create a custom vaccine for each individual case.

It turns out tobacco is just what the doctor ordered. It can provide a quicker and potentially cheaper alternative to conventional vaccine production. The gene that codes for a protein unique to a patient’s tumour is first extracted from the tumour and then inserted into a virus known to infect tobacco. The plant becomes a factory where the tobacco virus induces the production of large quantities of the required protein, which then is collected from the plant's leaves. The non-Hodgkin’s lymphoma vaccine produced using tobacco is still in clinical trials, but it has already been proven safe and successful in causing an immune response. The vaccine can be ready for use within weeks of a patient being diagnosed with the disease, compared to the months it would take to produce a vaccine using conventional methods.

Pharming can also be used to produce therapeutic proteins designed to replace an absent or non-functional protein. In this case, the DNA sequence that codes for the functional human protein is inserted into a host. For example, a drug to replace a defective protein associated with Gaucher disease is the first plant pharmed medicine to be approved by the US Food and Drug Administration for use in humans. It is made using cultured carrot cells as the host.

Did you know? Whole plant pharming could bring the cost of treatment for Gaucher disease down to as little as 0.1% of conventional methods using mammalian cells.Cultured plant cell pharming is not as cost effective as whole plant pharming. However, it allows more consistency between batches and yields a purer product. This is one reason why plant cell culture pharmed products will likely have an easier time overcoming regulatory hurdles. The pharmed drug used for the treatment of Gaucher disease costs $150,000 per patient per year. That's 25% less than the alternative drug produced in mammalian cells.

Growing plants in a field is an inexpensive method of producing pharmaceuticals. Conventional medical proteins that require mammalian cells to be grown in high tech bioreactors are expensive to produce. However, there is a risk of environmental contamination with plant pharming. One such case in 2002 raised significant fears and caused a temporary slowdown in pharming research. Using greenhouses or non-food crops like tobacco decrease the risk of contaminating the food chain.

Many pharmed medical proteins are being researched and, if they come to fruition, many medicines could become less expensive and more readily available.

Lean More!

Good and Evil: A Cancer Vaccine from Tobacco Plants (Scientific American)

http://www.scientificamerican.com/article.cfm?id=cancer-vaccine-tobacco-plants First plant-made drug on the market (Amy Maxmen, Nature.com News Blog)

http://blogs.nature.com/news/2012/05/first-plant-made-drug-on-the-market.html Planet Biotechnology

http://www.planetbiotechnology.com/ Pharming the Future (University of Calgary)

http://www.ucalgary.ca/pharmingthefuture/ The Prodigene Incident (Case Studies in Agricultural Biosecurity, Federation of American Scientists)

http://www.fas.org/biosecurity/education/dualuse-agriculture/2.-agricultural-biotechnology/prodigene-incident.html

Other References

McCormick, AA. 2011. Tobacco derived cancer vaccines for non-Hodgkin’s lymphoma: Perspectives and progress. Human Vaccines 7:305-312. Arntzen CJ. 2008. Using Tobacco to Treat Cancer. Science 321:1052-1053. Hodson H, Le Page M. (2012) Field of dreams. New Scientist. 214:50-51. Obembe OO. et al. 2011. Advances in plant molecular farming. Biotechnology Advances. 29:210-222. Xu J et al. 2012. Green factory: Plants as bioproduction platforms for recombinant proteins. Biotechnology Advances. 30:1171-1184. Paul M. et al. 2011. Molecular pharming: Future targets and aspirations. Human Vaccines 7:375-382. Elstein D, Zimran A. 2011. Recent Advances in Treatment Approaches to Gaucher Disease. Current Pharmaceutical Biotechnology. 12: 854-860.

Meredith Hanel

Meredith earned her PhD in medical genetics and spent many years at the lab bench researching in developmental biology and medicine. Meredith writes about science and is also involved in science outreach in elementary schools. She enjoys learning about clever biotechnology and loves to find out the biology behind just about anything in nature.

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