Clearing The Air

Thursday, April 15, 2004

Tobacco plant researched as a cure for cancer

http://www.dispatch.co.za/2001/08/06/features/TOBACCO.HTM

Tobacco used to fight cancer

COULD the much-maligned tobacco plant be used to help cancer patients? A California biotech company says it can, and it has set up shop in tobacco country to prove it.

Large Scale Biology of Vacaville, California, has built a commercial "biopharmaceutical production facility" in Owensboro, Kentucky. It is one of a handful of companies harnessing plants to produce useful human proteins.

Genetic engineers already use many different ploys to manufacture human proteins, such as insulin and growth hormones. Often, they isolate a human gene that carries the code for making a protein and splice it into yeast or bacteria, which multiply in fermentation vats.

Other methods include putting genes into cancer cells, which grow endlessly in lab cultures, or into farm animals, which make the proteins in their milk.

Now, companies are doing the same thing by the acre. They hope molecular farming, as some call it, will be cheaper and more efficient.

"We borrow the plant's cellular machinery," said Barry Bratcher, Large Scale Biology's biomanufacturing director. "The plant is just a host for us."

Tobacco is a big bulky plant that produces lots of greenery, and it is one scientists have already had plenty of practice genetically manipulating in the lab.

Large Scale Biology has contracts with four local farmers to grow a combined 27 acres of tobacco for research. Tobacco is also grown in the company's five greenhouses in Owensboro.

"It is ironic that tobacco might actually be used to create health instead of reducing health," said chief executive officer Bob Erwin.

Already, the company has begun early-stage testing of a tobacco-produced vaccine intended to trigger the body's immune system to fight non-Hodgkin's lymphoma. Each dose would be a customised protein, made by mutant genes taken from the patient's own cancer cells.

In theory, the proteins should stimulate the body to turn against the cancer.

If the vaccine works, the company says it will produce a plant that can make 15000 individualised doses a year.

The company also is considering human testing of a treatment for Fabry's disease. The therapy is a tobacco-made copy of a normal human enzyme, needed to break down fats, that is missing in victims of the disease.

In earlier stages is a collaboration with the US Navy and the National Institutes of Health to use tobacco to make stem cells grow. The goal is to find a natural human protein that will multiply blood-forming stem cells that have been isolated from the bone marrow.

Stem cells are the source of all human tissue. Those taken from early-stage embryos can grow into any cell in the body, and they will divide forever in test tubes. However, because they are derived from embryos discarded during in vitro fertilisation, many people believe their use is unethical.

Adults also have stem cells. Even though they can be isolated from the brain and other organs, they are difficult to grow on demand.

A team of Navy and NIH researchers, led by Dr John Chute, is attempting to produce a protein that will make blood stem cells divide repeatedly in a test tube. They already have evidence that the body makes such a protein. The collaboration with Large Scale Biology is intended to find the gene responsible so it can be manufactured in quantity.

Chute said the protein could be extremely useful for conducting gene therapy to correct inherited blood diseases, such as sickle cell anaemia.

The idea: isolate a few of the exceedingly rare stem cells from the victim's marrow, then use the protein to produce many more copies of them. This will leave doctors with enough stem cells to attempt gene therapy, replacing the disease-causing genes with healthy copies. The repaired stem cells would be returned to repopulate the patient's marrow.

The work could also have wartime applications. Radiation and chemical weapons can destroy the bone marrow, leaving only a few stem cells. On their own, these cells may reproduce too slowly to prevent death. But victims might be rescued by removing some of the remaining cells, building them up in a lab dish, and then returning them to restore the marrow.

Dr Larry Goldstein, professor of cellular and molecular education at the University of California, San Diego, cautioned that such research is difficult.

"I hope they'll be successful, but I think it's unrealistic to expect rapid success," Goldstein said. "Lots of companies and labs have been working on this for years and it's a painstakingly slow process to do this sort of thing."

However, Erwin said his company hopes to manufacture the stem cell factor soon, using tobacco plants in Owensboro.

"We would like to get the gene identified in the next year and start clinical trials with the product in two years," he said. -- Sapa-AP